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Convective Heat Transfer Coefficient Model Under Nanofluid Minimum Quantity Lubrication Coupled with Cryogenic Air Grinding Ti–6Al–4V
Abstract
Under the threat of serious environmental pollution and resource waste, sustainable development and green manufacturing have gradually become a new development trend. A new environmentally sustainable approach, namely, cryogenic air nanofluid minimum quantity lubrication (CNMQL), is proposed considering the unfavorable lubricating characteristic of cryogenic air (CA) and the deficient cooling performance of minimum quantity lubrication (MQL). However, the heat transfer mechanism of vortex tube cold air fraction by CNMQL remains unclear. The cold air fraction of vortex tubes influences the boiling heat transfer state and cooling heat transfer performance of nanofluids during the grinding process. Thus, a convective heat transfer coefficient model was established based on the theory of boiling heat transfer and conduction, and the numerical simulation of finite difference and temperature field in the grinding zone under different vortex tube cold air fractions was conducted. Simulation results demonstrated that the highest temperature initially declines and then rises with increasing cold air fraction. Afterward, this temperature reaches the lowest peak (192.7 °C) when the cold air fraction is 0.35. Experimental verification was conducted with Ti–6Al–4V to verify the convective heat transfer coefficient model. The results concluded that the low specific grinding energy (66.03 J/mm3), high viscosity (267.8 cP), and large contact angle (54.01°) of nanofluids were obtained when the cold air fraction was 0.35. Meanwhile, the lowest temperature of the grinding zone was obtained (183.9 °C). Furthermore, the experimental results were consistent with the theoretical analysis, thereby verifying the reliability of the simulation model.
... The In situ U-value testing explains how the thermal transmission characteristics of building materials like walls, floors and roofs are measured using a heat flow meter (Kim et al., 2022). The U-value measures how effectively building elements or fabric prevent heat loss to the external environment, influencing building energy efficiency (Zhang et al., 2020). Using the U-value in retrofit decision-making enables informed choices regarding the necessary insulation levels before retrofitting and evaluating the insulation's performance after retrofitting (Zhang et al., 2020). ...
... The U-value measures how effectively building elements or fabric prevent heat loss to the external environment, influencing building energy efficiency (Zhang et al., 2020). Using the U-value in retrofit decision-making enables informed choices regarding the necessary insulation levels before retrofitting and evaluating the insulation's performance after retrofitting (Zhang et al., 2020). The International Organization for Standardization recommends ISO 9869 as the in situ U-value determination standard (ISO) (Choi and Ko, 2019). ...
... The determination of the U-value involves several steps or elements. Firstly, it entails choosing the right heat flow meters with a minimum accuracy of 65% (Zhang et al., 2020). It is important to note that larger heat flow meters offer greater sensitivity but are more challenging to mount on a wall. ...
Purpose-The purpose of this study is to investigate and analyse the potential of existing buildings in the UK to contribute to the net-zero emissions target. Specifically, it aims to address the significant emissions from building fabrics which pose a threat to achieving these targets if not properly addressed.
Design/methodology/approach-The study, based on a literature review and ten (10) case studies, explored five investigative approaches for evaluating building fabric: thermal imaging, in situ U-value testing, airtightness testing, energy assessment and condensation risk analysis. Cross-case analysis was used to evaluate both case studies using each approach. These methodologies were pivotal in assessing buildings' existing condition and energy consumption and contributing to the UK's net-zero ambitions.
Findings-Findings reveal that incorporating the earlier approaches into the building fabric showed great benefits. Significant temperature regulation issues were identified, energy consumption decreased by 15% after improvements, poor insulation and artistry quality affected the U-values of buildings. Implementing retrofits such as solar panels, air vents, insulation, heat recovery and air-sourced heat pumps significantly improved thermal performance while reducing energy consumption. Pulse technology proved effective in measuring airtightness, even in extremely airtight houses, and high airflow and moisture management were essential in preserving historic building fabric.
Originality/value-The research stresses the need to understand investigative approaches' strengths, limitations and synergies for cost-effective energy performance strategies. It emphasizes the urgency of eliminating carbon dioxide (CO 2) and greenhouse gas emissions to combat global warming and meet the 1.5°C threshold.
... The grinding fluid in the heat exchange zone of the LSG-GW exerts convective heat exchange on the grinding surface to carry away the heat generated in the contact area. However, the calculation of convective heat transfer coefficient, which can characterize the strength of heat transfer capacity in the grinding arc, has been the focus and difficulty of research [25][26][27][28] . In addition, in terms of heat transfer performance, the latest research findings show that when the grinding fluid is ejected from the nozzle and continues to flow by inertia, the speed is gradually reduced. ...
... The boundary conditions are given for Eq. (28). ...
... It may be approximated by == .After correcting it to obtain the solution result when Pr≠1. When Pr = 1, since all variables in Eq.(28) are dimensionless quantities, u * and Θ should have exactly the same solution. and then: ...
In view of the high specific removal energy, high heat generation rate, low heat transfer efficiency, easy to produce local high temperature and grinding burns, new macro-structured grinding wheel forms were proposed, namely, Large Spiral-angle Grooved Grinding Wheels (LSG-GW, β > 85°) and Large Spiral-angle flow Disturbance Grooved Wheels (LSDG-GW). Considering the influence of wheel parameters, groove parameters and process parameters, an analytical model of the airflow field in the wedge area and contact area of LSG-GW was established. Analytical model of gas-liquid two-phase flow field and theoretical model of convective heat transfer coefficient distribution in heat transfer channels were established. The results showed that increasing the groove width, groove depth and the spiral angle can reduce the pressure of the flow field in the air barrier layer and make it easier for the grinding fluid to enter the grinding contact area. The LSDG-GW further reduces the grinding fluid back flow and side flow intensity, proving that the flow disturbance structure can bring in more grinding fluid into the grinding contact area. A theoretical model for the distribution of convective heat transfer coefficient in the grinding contact area was derived, and the analysis results proved that the flow disturbance structure can significantly improve the convective heat transfer coefficient in the grinding contact area. The LSDG-GW, as a new macro surface structured grinding wheel, has a very promising application in the high efficiency and high precision grinding process of difficult-to-machine alloy materials.
... CAMQL technology was proposed in [8][9][10]: supply of a minimum quantity of lubricant in a cooled air flow. That reduces the thermal load in grinding and improves the quality of the machined surface. ...
... The grinding conditions are as follows: the azimuthal wheel speed = 35 m/s; the table supply S = 6 m/min; the supply depth t = 0.01 mm/pass; the margin removed per experiment h = 0.5 mm; and the number of parallel experiments is three. Two rates of lubricant supply are chosen on the basis of literature data for MQL and CAMQL technology in grinding [8,9,15,16]: p = 30 and 50 mL/h of soybean oil [10,13]. That minimizes the environmental impact [2]. ...
... Cold air at T = −8, −3, and 0°С is supplied at rates P = 4, 8, and 12 m 3 /h, respectively. The air flow rate is chosen on the basis of data in [8,9]. By 3D printing, a nozzle is produced and placed at the center of a round end piece; the nozzle inclination with respect to the workpiece is 15°. ...
Abstract—Two grinding technologies with air cleaning of the wheel surface are compared: the baseline system
ensures minimum lubricant supply; the other includes additional air cooling of the wheel. The influence of
the lubricant supply and air f low rate on the grinding of a heat-stable nickel alloy is considered.
... The grinding fluid in the heat exchange zone of the LSG-GW exerts convective heat exchange on the grinding surface to carry away the heat generated in the contact area. However, the calculation of convective heat transfer coefficient, which can characterize the strength of heat transfer capacity in the grinding arc, has been the focus and difficulty of research [19][20][21]. In addition, in terms of heat transfer performance, the latest research findings show that when the grinding fluid is ejected from the nozzle and continues to flow by inertia, the speed is gradually reduced. ...
... The graph shows that the convective heat transfer coefficient increases with the increase of grinding speed. However, in the actual grinding process, the grinding speed and the macro-convective heat transfer coefficient of the grinding fluid do not always maintain a positive correlation [21]. This is because as grinding speed increases, grinding temperature rises as well, and when the temperature above the boiling point of the grinding fluid, the grinding fluid's macro-convective heat transfer coefficient decreases instead. ...
In view of the high specific removal energy, high heat generation rate, low heat transfer efficiency, and easy-to-produce local high-temperature and grinding burns, new macro-structured grinding wheel forms were proposed, namely, large spiral angle grooved grinding wheels (LSG-GW, β>85°) and large spiral angle flow disturbance grooved wheels (LSDG-GW). Considering the influence of wheel parameters, groove parameters, and process parameters, an analytical model of the airflow field in the wedge area and contact area of LSG-GW was established. Analytical model of gas–liquid two-phase flow field and theoretical model of convective heat transfer coefficient distribution in heat transfer channels were established. The results showed that increasing the groove width, groove depth, and the spiral angle can reduce the pressure of the flow field in the air barrier layer and make it easier for the grinding fluid to enter the grinding contact area. The LSDG-GW further reduces the grinding fluid back flow and side flow intensity, proving that the flow disturbance structure can bring in more grinding fluid into the grinding contact area. A theoretical model for the distribution of convective heat transfer coefficient in the grinding contact area was derived, and the analysis results proved that the flow disturbance structure can significantly improve the convective heat transfer coefficient in the grinding contact area. The LSDG-GW, as a new macro-surface-structured grinding wheel, has a very promising application in the high-efficiency and high-precision grinding process of difficult-to-machine alloy materials.
... Their results showed that Low molecular weight Polyethylene mine (PEI) was more effective than extra molecular weight Polyethylene mine (PEI) in virus gene delivery. other researchers have shown that the method is effective in vivo gene delivery [229][230][231][232][233][234]. ...
With the rapid development of nanotechnology in the recent decade, novel DNA and RNA delivery systems for
gene therapy have become available that can be used instead of viral vectors. These non-viral vectors can be
made of a variety of materials, including inorganic nanoparticles, carbon nanotubes, liposomes, protein and
peptide-based nanoparticles, as well as nanoscale polymeric materials. They have as advantages over viral
vectors a decreased immune response, and additionally offer flexibility in design, allowing them to be functionalized and targeted to specific sites in a biological system with low cytotoxicity.gene therapy keeps hopes a
life for the treatment of a wide range of diseases such as cancer, nano particles are now known as promising
carriers for the effective and safe vectors of genes to specific cells or tissues. This could provide alternative
therapies for conventional approaches that use viruses as gene carriers. The expression of genetic material such
as DNA, RNA into cells and tissues has raised considerable hopes for therapeutic and diagnostic purposes. But
getting nucleic acids into the cell also faces challenges. These challenges are less for non-virus carriers as a gene
and drug vectors method than for viral or free vectors and are therefore considered less risky and more
appropriate. of expanding nonverbal nano carriers, we will look at a few of these nano carriers, penicillin, PEI,
PLGA, silica, block copolymer, Quantum dot, gold nano particles, and common carbon nano tubes. Problems
include the use of nano particles such as polymer nano particles, liposomes, solid lipid particles, in targeted gene
vectors will be investigated. Gene-based therapy is the intentional modulation of gene expression in specific cells
to treat pathological conditions. This modulation is accomplished by introducing exogenous nucleic acids such as
DNA, mRNA, small interfering RNA (siRNA), microRNA (miRNA) or antisense oligonucleotides. Given the large
size and the negative charge of these macromolecules, their delivery is typically mediated by carriers or vectors.
In this Review, we introduce the biological barriers to gene delivery in vivo and discuss recent advances i
... In recent years, the authors paved their attention towards the study of heat transfer applications using hybrid type nanofluids. Recently, Ramesh et al. [43], Shahsavar et al. [44], Yaseen et al. [45], Liu et al. [46], Mahmood et al. [47] and Zhang et al. [48] discussed the nanofluid for engineering applications. These studies revealed that inclusions of nanoparticles in common solvents is a reliable way to make them more effective. ...
... Zhang et al. [30] in their experimental research utilized an environmentally friendly coolant named cryogenic air nanofluid. In their work, a model of convective heat transfer was validated by grinding Ti-6Al-4V alloy. ...
Polymeric resins are becoming increasingly popular in medical and engineering applications due to their properties, such as their low weight, high strength, corrosion resistance, non-allergenicity, and extended service life. The grinding process is used to convert these materials into desired products, offering high accuracy and surface quality. However, grinding generates significant heat, which can potentially degrade the material. This study investigates the grinding of acrylic-based resins, spe-cifically focusing on the interplay between the grind zone temperature and surface finish. The low glass transition temperature (57 °C) of the acrylic necessitates the precise control of the grinding parameters (spindle speed, feed rate, depth of cut, and grinding wheel grain size), to maintain a low temperature and achieve high-quality machining. Thermal imaging and thermocouples were em-ployed to measure the grind zone temperature under various grinding conditions. This study in-vestigates the influence of four parameters: spindle speed, feed rate, depth of cut, and grinding wheel grain size. The best surface finish (Ra: 2.5 µm) was obtained by using a finer-grained (80/Ø 0.18 mm) grinding wheel, combined with slightly adjusted parameters (spindle speed: 11.57 m/s, feed rate: 0.406 mm/rev, depth of cut: 1.00 mm), albeit with a slightly higher grind zone temperature (~54 °C). This study highlighted the importance of balancing the grind zone temperature and surface finish for the optimal grinding of acrylic-based resins. Further, this research finds that by carefully controlling the grinding parameters, it is possible to achieve both a high surface quality and prevent material degradation. The research findings could be highly valuable for optimizing the grinding process for various medical and engineering applications.
... Zhang et al. [57] established a convective heat transfer coefficient model based on boiling heat transfer and thermal conductivity theory and numerically simulated the temperature field of the grinding zone under different vortex tube cryogenic air flow rates. The simulation results were only 5.1% different from the experimental data, and it indicated that the theoretical model has a high accuracy. ...
The cutting fluid plays an important role in lubrication, cooling, chip removal, and rust protection in mechanical manufacturing. The waste-cutting fluid can pose a threat to the water environment and even human health. The minimum quantity lubrication (MQL) technology can meet the requirements of clean manufacturing, and it has been widely recognized as a replacement for traditional flood-cutting technology. As an emerging green cutting technology, it has broad application prospects. The latest progress in MQL machining technology is reviewed, and the cutting performance of MQL is elaborated in this article. Firstly, the composition and implementation form of the MQL system were elaborated. The impact of the MQL system parameters on cutting performance was also illustrated in this part. Secondly, the combination of MQL technology, low-temperature technology synergistic effect of additives, and the atomization and hardware improvement of MQL was introduced. Thirdly, the cutting performance of MQL technology on cutting force, cutting temperature, residual stress, tool wear, and surface quality was analyzed. Finally, the limitations of MQL technology were discussed, and its development direction was prospected. It provides suggestions for the engineering application of MQL technology.
... Their results showed that Low molecular weight Polyethylene mine (PEI) was more effective than extra molecular weight Polyethylene mine (PEI) in virus gene delivery. other researchers have shown that the method is effective in vivo gene delivery [229][230][231][232][233][234]. ...
With the rapid development of nanotechnology in the recent decade, novel DNA and RNA delivery systems for
gene therapy have become available that can be used instead of viral vectors. These non-viral vectors can be
made of a variety of materials, including inorganic nanoparticles, carbon nanotubes, liposomes, protein and
peptide-based nanoparticles, as well as nanoscale polymeric materials. They have as advantages over viral
vectors a decreased immune response, and additionally offer flexibility in design, allowing them to be functionalized
and targeted to specific sites in a biological system with low cytotoxicity.gene therapy keeps hopes a
life for the treatment of a wide range of diseases such as cancer, nano particles are now known as promising
carriers for the effective and safe vectors of genes to specific cells or tissues. This could provide alternative
therapies for conventional approaches that use viruses as gene carriers. The expression of genetic material such
as DNA, RNA into cells and tissues has raised considerable hopes for therapeutic and diagnostic purposes. But
getting nucleic acids into the cell also faces challenges. These challenges are less for non-virus carriers as a gene
and drug vectors method than for viral or free vectors and are therefore considered less risky and more
appropriate. of expanding nonverbal nano carriers, we will look at a few of these nano carriers, penicillin, PEI,
PLGA, silica, block copolymer, Quantum dot, gold nano particles, and common carbon nano tubes. Problems
include the use of nano particles such as polymer nano particles, liposomes, solid lipid particles, in targeted gene
vectors will be investigated. Gene-based therapy is the intentional modulation of gene expression in specific cells
to treat pathological conditions. This modulation is accomplished by introducing exogenous nucleic acids such as
DNA, mRNA, small interfering RNA (siRNA), microRNA (miRNA) or antisense oligonucleotides. Given the large
size and the negative charge of these macromolecules, their delivery is typically mediated by carriers or vectors.
... The results of viscosity measurements are shown in Fig. 5. Although low viscosity is of critical importance in the MQL arrangement, so that the oil can be pulverized better and form a mist cloud [38], it is necessary that the nanofluids used as lubricants have a high viscosity in order to form a more effective film layer in the wear zone. For this purpose, viscosity measurements of graphene (nano-MQL1), hBN (nano-MQL2) and graphene/hBN hybrid nanofluids (nano-MQL3) were made and the results are given in Fig. 6. ...
Titanium and its alloys are widely utilized in the biomedical sector, they still exhibit poor tribological properties and low wear resistance when employed against even weaker substances. The poor hardness, instability, high coefficient of friction, low load-carrying capacity, and insufficient resistance to not only abrasive but also adhesive wear are further disadvantages of titanium alloys. The focus of this investigation is on the tribological performance of Ti-6Al-4 V alloy in contact with WC carbide abrasive balls when subjected to nanodoped cooling and lubrication conditions. Tribological experiments were executed on Ti-6Al-4 V flat samples using a ball-on-flat tribometer in dry hybrid graphene/boron nitride combination nanoparticles (MQL, nano-3), nanographene with MQL (nano-1), and boron nitride with MQL (nano-2) conditions. After that, the most significant tribological characteristics were investigated, including volume loss, friction coefficient, wear rate, and micrographic structures. The outcomes also demonstrated that the hybrid nanoparticle situation experienced the least amount of volume loss.
... Their results showed that Low molecular weight Polyethylene mine (PEI) was more effective than extra molecular weight Polyethylene mine (PEI) in virus gene delivery. other researchers have shown that the method is effective in vivo gene delivery [229][230][231][232][233][234]. ...
With the rapid development of nanotechnology in the recent decade, novel DNA and RNA delivery systems for gene therapy have become available that can be used instead of viral vectors. These non-viral vectors can be made of a variety of materials, including inorganic nanoparticles, carbon nanotubes, liposomes, protein and peptide-based nanoparticles, as well as nanoscale polymeric materials. They have as advantages over viral vectors a decreased immune response, and additionally offer flexibility in design, allowing them to be functionalized and targeted to specific sites in a biological system with low cytotoxicity. gene therapy keeps hopes a life for the treatment of a wide range of diseases such as cancer, nano particles are now known as promising carriers for the effective and safe vectors of genes to specific cells or tissues. this could provide alternative therapies for conventional approaches that use viruses as gene carriers. the expression of genetic material such as DNA, RNA into cells and tissues has raised considerable hopes for therapeutic and diagnostic purposes. but getting nucleic acids into the cell also faces challenges. These challenges are less for non-virus carriers as a gene and drug vectors method than for viral or free vectors and are therefore considered less risky and more appropriate. of expanding nonverbal nano carriers, we will look at a few of these nano carriers, penicillin, PEI, PLGA, silica, block copolymer, Quantum dot, gold nano particles, and common carbon nano tubes. Problems include the use of nano particles such as polymer nano particles, liposomes, solid lipid particles, in targeted gene vectors will be investigated. Gene-based therapy is the intentional modulation of gene expression in specific cells to treat pathological conditions. This modulation is accomplished by introducing exogenous nucleic acids such as DNA, mRNA, small interfering RNA (siRNA), microRNA (miRNA) or antisense oligonucleotides. Given the large size and the negative charge of these macromolecules, their delivery is typically mediated by carriers or vectors. In this Review, we introduce the biological barriers to gene delivery in vivo and discuss recent advances in material sciences, nanotechnology and nucleic acid chemistry that have yielded promising non-viral delivery systems, some of which are currently undergoing testing in clinical trials. The diversity of these systems highlights the recent progress of gene-based therapy using non-viral approaches
... Moreover, cutting fluid causes serious 36:11 pollution to the environment and endangers human health [9,10]. Milling must comply with current trends and meet the need for a green process to achieve sustainable development [11,12]. Minimum-quantity lubrication (MQL) is an effective and green method, also known as near-dry machining [13] or micro-lubrication [14], which has been used to improve the machining performances [15]. ...
Nanofluid minimum quantity lubrication (NMQL) is a green processing technology. Cottonseed oil is suitable as base oil because of excellent lubrication performance, low freezing temperature, and high yield. Al 2 O 3 nanoparticles improve not only the heat transfer capacity but also the lubrication performance. The physical and chemical properties of nanofluid change when Al 2 O 3 nanoparticles are added. However, the effects of the concentration of nanofluid on lubrication performance remain unknown. Furthermore, the mechanisms of interaction between Al 2 O 3 nanoparticles and cottonseed oil are unclear. In this research, nanofluid is prepared by adding different mass concentrations of Al 2 O 3 nanoparticles (0, 0.2%, 0.5%, 1%, 1.5%, and 2% wt) to cottonseed oil during minimum quantity lubrication (MQL) milling 45 steel. The tribological properties of nanofluid with different concentrations at the tool/workpiece interface are studied through macro-evaluation parameters (milling force, specific energy) and micro-evaluation parameters (surface roughness, micro morphology, contact angle). The result show that the specific energy is at the minimum (114 J/mm ³ ), and the roughness value is the lowest (1.63 μm) when the concentration is 0.5 wt%. The surfaces of the chip and workpiece are the smoothest, and the contact angle is the lowest, indicating that the tribological properties are the best under 0.5 wt%. This research investigates the intercoupling mechanisms of Al 2 O 3 nanoparticles and cottonseed base oil, and acquires the optimal Al 2 O 3 nanofluid concentration to receive satisfactory tribological properties.
... The lower thermal conductivity and elastic modulus will induce strong adhesion effects during the surface machining processes. The traditional contact processing methods are difficult to ensure the processing efficiency and surface quality for the large-area titaniferous alloy parts [3,4]. Aiming at the problems, scholars have developed a variety of non-contact processing methods, such as abrasive flow machining (AFM) [5], abrasive water jet (AWJ) [6], and soft abrasive flow (SAF) [7], in which the key technologies are the regulation of the abrasive flow field and surface quality [8,9]. ...
Soft abrasive flow (SAF) finishing has advantages in precise processing for titaniferous alloy parts with large-area surfaces. However, the processing efficiency and surface quality of current SAF methods require to be improved. To address the issues, a novel gas–liquid-solid three-phase rotary abrasive flow polishing method (RGLSP) is proposed based on the microbubble cavitation effect. Referring to the energy conservation principles of bubbles group movement, an improved realizable k-ε turbulence model is set up. Based on the above model, a mechanical dynamic model of the machining apparatus is established to obtain the flow field distribution of different structural parameters. The simulated results show that the pitch-down angle determines the distribution of the rotary flow field, and an optimized processing apparatus is developed. The machining experiments show that the proposed RGLSP method can improve the machining efficiency by 60%, and the surface roughness can reach Ra 0.1 μm with lower surface defects. The RGLSP can provide an important reference direction for low-carbon emission processing.
... The results show that the composite process of cold air and NMQL has the best cooling effect, followed by low-temperature cold air and NMQL. Furthermore, Zhang et al. [155] established a CHTC model of cold air nanofluids in vortex tubes based on boiling heat transfer conduction theory and conducted numerical simulations of the finite difference and temperature field in the grinding zone under different cold air fractions in vortex tubes. The simulation results show that with an increase in the cold air fraction, the maximum temperature initially decreases and then increases. ...
Nanofluids are efficient heat transfer media that have been developed over the past 27 years and have been widely used in the electronic microchannel, engine, spacecraft, nuclear, and solar energy fields. With the high demand for efficient lubricants in manufacturing, the application of nanofluids in machining has become a hot topic in academia and industry. However, in the context of the huge amount of literature in the past decade, existing review cannot be used as a technical manual for industrial applications. There are many technical difficulties in establishing a mature production system, which hinder the large-scale application of nanofluids in industrial production. The physicochemical mechanism underlying the application of nanofluids in machining remains unclear. This paper is a complete review of the process, device, and mechanism, especially the unique mechanism of nanofluid minimum quantity lubrication under different processing modes. In this paper, the preparation, fluid, thermal, and tribological properties of nanofluids are reviewed. The performance of nanofluids in machining is clarified. Typically, in friction and wear tests, the coefficient of friction of jatropha oil-based alumina nanofluids is reduced by 85% compared with dry conditions. The cutting fluid based on alumina nanoparticles improves the tool life by 177–230% in hard milling. The addition of carbon nanotube nanoparticles increases the convective heat transfer coefficient of normal saline by 145.06%. Furthermore, the innovative equipment used in the supply of nanofluids is reviewed, and the atomization mechanisms under different boundary conditions are analyzed. The technical problem of parameterized controllable supply system is solved. In addition, the performance of nanofluids in turning, milling, and grinding is discussed. The mapping relationship between the nanofluid parameters and the machining performance is clarified. The flow field distribution and lubricant wetting behavior under different tool-workpiece boundaries are investigated. Finally, the application prospects of nanofluids in machining are discussed. This review includes a report on recent progress in academia and industry as well as a roadmap for future development.
... Some kinds of nanoparticles/micron particles are added into the cooling fluid for improving grinding performance. Nanoparticles/micron particles including molybdenum disulfide (MoS 2 ) [35,36], nanodiamond (ND) [37], silicon carbide (SiC) [38,39], alumina (Al 2 O 3 ) [40], carbon nanotubes (CNTs) [41,42], carbon (C) [43], and so on are commonly used [44][45][46]. The experiments showed that graphite and MoS 2 have a lubrication effect in grinding hard and brittle materials [35]. ...
Prolonged polishing deteriorates the shape accuracy of an optical element and reduces production efficiency simultaneously. In order to reduce the amount of polishing and polishing time, even obtain polish-free fine surfaces, a cerium oxide (CeO2) slurry-enhanced grinding (SEG) is investigated. However, the lack of in-depth mechanism explanation limits the optimization and application of SEG. In this research, a novel theoretical model was established to predict the surface roughness of the workpiece processed by CeO2 SEG. The modeling considered the effects of the protrusion height of active grains in the grinding wheel and the sizes and mass fractions of CeO2 particles in the grinding zone on undeformed chip thickness (UCT). Then, the mechanism of CeO2 SEG was investigated through the nanoindentation method. Indentation hardness and energy spectrum of the surface were estimated to verify the softened layer. The results showed that the model of surface roughness was well consistent with the experiment. CeO2 particle size significantly influenced the surface roughness than the mass fraction. The load-bearing effect of larger CeO2 particle size reduced the protruding height of the grinding wheel grains and reduced the UCT to a greater extent in the grinding process. The chemical reaction between CeO2 slurry and BK7 glass results in a softening layer which enhances the critical load and critical depth of the ductile–brittle transition of grinding. Finally, the optimized parameters were used for CeO2 SEG of ellipsoid BK7 optics and obtained the high surface quality.
... Some kinds of nano/micron particles are added into the cooling fluid for improving grinding performance. Nano/micron particles including molybdenum disulfide (MoS2) [35,36], nanodiamond (ND) [37], silicon carbide (SiC) [38], alumina (Al2O3) [39], carbon nanotubes (CNTs) [40,41] and so on are commonly used [42][43][44]. The experiments showed that the graphite and MoS2 have a lubrication effect in grinding hard and brittle materials [35]. ...
Prolonged polishing deteriorates the shape accuracy of an optical element and reduces production efficiency simultaneously. In order to reduce the amount of polishing and polishing time, even obtain polish-free fine surfaces, a cerium oxide (CeO 2 ) slurry assisted grinding (SAG) is investigated. A novel theoretical model was established to predict the surface roughness of the workpiece processed by CeO 2 SAG. The modelling considered the effects of the protrusion height of active grains in the grinding wheel and the sizes and mass fractions of CeO 2 particles in the grinding zone on undeformed chip thickness (UCT). Then, the mechanism of CeO 2 SAG was investigated through nanoindentation method. Indentation hardness and energy spectrum of the surface were estimated to verify the softened layer. The results showed that the model of surface roughness was well consistent with the experiment. The CeO 2 particle size significantly influenced on the surface roughness than the mass fraction. The load-bearing effect of larger CeO 2 particle size reduced the protruding height of the grinding wheel grains and reduced the UCT to a greater extent in grinding process. The chemical reaction between CeO 2 slurry and BK7 glass results in a softening layer which enhances the critical load and critical depth of ductile-brittle transition of grinding. Finally, the optimized parameters were used for CeO 2 SAG of an ellipsoid BK7 optics.
... The study revealed that the SCCO2 + MQL outperforms both dry and MQL burnishing in terms of burnishing force, temperature, and surface roughness [12] and that the difference between dry and MQL processing is small. Articles [13,14] present CAMQL (cold air with minimum quantity lubrication) studies where the optimal proportion of cold air needed to minimize temperature during processing was found. ...
Burnishing, the plastic deformation of the workpiece surface due to sliding contact with a tool called burnisher, is a finishing operation widely used in various industries. In this work, impacts of the initial surface roughness Ra of the workpiece being burnished, the nature of friction in the contact zone, and the clamping force on the stability and energy efficiency of burnishing have been investigated. Experiments have been conducted with and without lubricant, represented by low-viscosity deep-hydrogenated fraction of sour oils, at initial surface roughness Ra of 0.8 and 1.25 μm and variable (100–200 N) clamping force. A key process indicator, which largely controls mechanics of burnishing, the temperature in the tool-workpiece contact zone has been measured using natural thermocouple method. Microhardness of the workpiece surface after burnishing has also been measured. It has been shown that changes in the temperature of the tool-workpiece contact zone are proportional to the changes in the squared tool clamping force. This dependence appeared to be universal and equally applicable to burnishing with and without lubrication. Based on the analysis of the experimental data, а new criterion of the burnishing efficiency has been developed. The new criterion simplifies the choice of optimum operational parameters and helps in preventing adverse impacts of structural phase transformations in the workpiece surface layer that unavoidably lead to reduced product quality and operational reliability and in reducing tool wear, which is critically important in the case of dry burnishing. The obtained results show that the nature of friction accompanying the surface plastic deformation has a significant impact on the stability and energy efficiency of the burnishing process. While the clamping force is equally important for burnishing with and without lubrication, the initial roughness Ra has an impact on dry burnishing only. Application of minimum quantity lubrication (MQL) under experimental conditions typical for industrial burnishing is found to be favorable. In particular, it was shown that MQL not only enhances the stability of burnishing process and but also increases its energy efficiency by more than 20%.
... nanofluid under the MQL application is the most suitable solution in the terms of cost savings and pollution-free substance. Zhang et al. [26] performed experimentations on an environmentally friendly substance named cryogenic air nanofluid. The convective heat transfer coefficient model was validated experimentally using Ti-6Al-4 V. ...
In the light-activated work-holding devices, hardened adhesive residues on the fixture plate need to be removed to make it available for the subsequent work holding. There are several ways to remove the cured adhesive from the gripper, such as laser-based degradation, and softening and removing with high temperature pressured water wash. These processes are associated with the generation of carbon black, affecting transparency which compromises the efficiency of the light-activated device. A novel peripheral grinding-based cleaning process has been developed to strip the adhesive from the fixture plate. The present research is aimed to analyze the effect of variation in grinding parameters, viz., spindle speed, feed, depth of cut, and the grain size of the grinding wheel on the temperature of the adhesive being ground and cleaning of the adhesive-filled channel. Aggressive values of grinding parameters are selected to achieve the desired removal of adhesive, putting a step towards sustainability. Moreover, a comprehensive investigation of the temperature of the grinding zone and the grinding wheel is made by inspecting the effective cleaning of the cured adhesive-filled channel. Higher values of spindle speed (11.57 m/s) and feed (0.406 mm/rev) resulted in an improved, cleaned surface of the ground adhesive-filled channel. Moreover, the grinding wheel with a more prominent grain size (46/Ø 0.35 mm) and porosity was proved to be more effective in the cleaning process by reducing and maintaining the grinding temperature (~52 °C) of the adhesive-filled channel.
... Results exhibited that the specific grinding energy of the hybrid nanofluids was reduced by 39% compared with that of deionized water, and there was no thermal damage on the workpiece surface. Zhang et al. [26] proposed using cryogenic air nanofluid minimum quantity lubrication (CNMQL) to improve the cooling and lubrication conditions in the grinding zone. The grinding temperature field simulation results showed that us-ing CNMQL could effectively reduce the grinding temperature, and the lowest grinding zone temperature (192.7 °C) was reached when the cold air fraction was 0.35. ...
The traditional flood cooling method is hard to dissipate the massive amount of heat accumulated in the grinding zone during the high-efficiency grinding process, which easily causes burnout of the workpiece that limits the increase of the processing efficiency. Employing an abrasive phyllotaxy arrangement and an internal cooling grinding wheel (ICGW) can augment the heat transfer of the coolant in the grinding zone to lower the grinding temperature. An abrasive phyllotaxy arrangement internal cooling grinding wheel that is a combination of an ICGW and abrasive phyllotaxy arrangement was proposed in this study. To optimize geometric dimensions and phyllotaxy coefficient of the abrasive phyllotaxy arrangement ICGW, simulation and experimental investigations were carried out to explore the effects of coolant (water-based ILs-MWCNTs/MoS2 hybrid nanofluids), grinding wheel diameters, and phyllotaxy growth coefficient on the heat transfer capability of the wheels. Within a specific range, the ICGWs with a smaller diameter and larger phyllotaxy growth coefficient show an advantage in fluid flow and heat transfer. Experimental results exhibit that, compared with the typical orderly arrangement, the grinding temperature and surface roughness of the ICGWs with the phyllotaxy pattern was reduced by about 20% and 50%, respectively. Under the same phyllotaxis coefficient, the grinding temperature and surface roughness obtained by the ICGWs with a smaller diameter were reduced by 10% and 22.3%, respectively. The residual compressive stress was elevated by 10.94%.
... There are four typical types to describe the moving heat source: rectangular model, parabolic model, triangular model, and inclined heat source, which were shown in Fig. 1. Triangular model is most suitable for plane grinding temperature distribution [17]. ...
As an energy-saving and eco-friendly combined machining, Grinding-strengthening (GS) technology has been widely applied. Because the strengthened layer is a critical factor affecting surface mechanical properties, it is worthwhile to study the predicting method of surface-strengthened layer. The relevance of strengthened layer and dynamic vibration signal of GS was studied in this paper. Firstly, the alternation direction implicit (ADI) method was creatively used to build a dynamic grinding temperature field system according to the Jager theory model, which can simulate the workpiece’s temperature at any time step during processing. Secondly, the strengthened depth was worked out based on the relationship between dynamic temperature variation and phase transformation character. Thirdly, a regenerative vibration system was developed, and different process parameters’ influences on grinding vibration were discussed in simulation. Lastly, the correlation of strengthened layer and vibration signal was analyzed by surface grinding experiments of AISI1045. Both simulation and experimental results proved that the grinding vibration signal includes abundant strengthened layer information. In addition, the probability density feature of grinding vibration signal was consistent with strengthened layer’s depth. The results also demonstrated the feasibility of predicting strengthened layer by vibration signal in GS process.
... The five heat transfer mechanisms of spray cooling during material removal [95,96] are liquid film heat transfer, liquid film surface convective heat transfer, surface nucleate boiling heat transfer, secondary nucleate boiling heat transfer, and ambient heat transfer. Fig. 5 also shows the four stages of boiling heat transfer of the lubricating medium with respect to temperature change [97,98]: non-boiling heat transfer stage, nucleate boiling stage, transition boiling stage, and stable film boiling stage. In the non-boiling zone, the heat transfer coefficient remains unchanged. ...
The tribological behavior of cutting is a decisive factor in changing the production cycle, cost, and quality of parts. Minimum quantity lubrication (MQL) based on environmentally friendly biolubricants can convert contact conditions in cutting zones, but it cannot meet the manufacturing requirements of difficult-to-machine materials in the continuous friction turning process. Under the boundary conditions of high temperature, high cutting speed, and high pressure at the tool–workpiece interface, the scientific issue of performance enhancement remains unclear and thus has been the focus of academic and industry research. Moreover, under the continuous cutting boundary condition, technology enhancement as a development trend has not yet been systematically reviewed. Wetting, friction reduction, and heat transfer mechanisms have also not yet been investigated. In this study, the cooling lubrication mechanism and technical iteration motivation of MQL were initially analyzed. Subsequently, a quantized comparative assessment of cutting force, cutting temperature, tool wear, and surface quality under enhanced environmentally friendly lubrication turning, including parts enhanced by nanoparticles, cryogenic medium, ultrasonic vibration, and textured tools, was performed. The technical performance, parameter optimization, and mechanism of enhanced MQL were comprehensively studied, and the development stages of biolubricant MQL turning (MQLT) were fully reviewed. Finally, the development trend of the theory and application of MQLT for difficult-to-machine materials was prospected. This study may be used by scientists to deeply understand the mechanism, tribological behavior, and development trend of lubrication in relation to continuous cutting.
... Therefore, scholars have proposed green cutting processes, such as dry cutting and minimum quantity lubrication (MQL) cutting. However, these processes cannot meet the needs of titanium alloy grinding due to the serious shortage of cooling and lubrication performance in dry cutting [20,21]. MQL uses compressed air to atomize a small amount of lubricant to form fine particle oil mist, improve its own migration and penetration activity, so as to play the role of cooling and lubrication [22][23][24]. ...
As a dielectric, biolubricant (vegetable oil) cannot maximize the efficiency of electrostatic atomization minimum quantity lubrication (EMQL). The lecithin-enhanced technology is expected to solve this technical bottleneck. The effects of lecithin on the electrophysiological properties of biolubricant (soybean oil) were investigated. Lecithin can increase the conductivity, viscosity, and charge mass ratio and reduce the surface tension of soybean oil. Comparative experiments show that the maximum average temperature rise of workpiece surface with MQL is 241.6 °C. The value under flooding, EMQL, and L+EMQL is reduced by 28.97%, 42.8%, and 48.92%, respectively, compared with MQL. The influence of lecithin mixing ratio on grinding performance was discussed. The minimum surface roughness value (0.49 μm) is obtained at the mixing ratio of 2:10.
... Cryogenic cooling aims to inject the low-temperature gas (commonly used air, LN 2 , and CO 2 [94,95]) cooled by the refrigeration system into the cutting area to replace the cutting fluid for lubrication, cooling, and chip removal, as shown in Fig. 14. Therefore, a minimal quantity of vegetable oil can be mixed to enhance the lubricity of low-temperature cold air [96]. Cryogenic cooling cutting technology includes the advantages of cryogenic airflow and minimum quantity lubrication [97]. ...
Realizing the integrated manufacturing of components with high specific strength and stiffness is easy using carbon fiber reinforced polymer (CFRP), which has become the preferred material for weight reduction and efficiency enhancement in the aerospace field. Massive connection holes are machined in assembly. However, CFRP is a multiphase material comprising fiber, resin, and interface at the mesoscopic level. Macroscopically, CFRP has the characteristics of heterogeneity, anisotropy, and heat sensitivity, thus easily causing delamination and burr, which limits its application. Only a few systematic analyses and reviews from the aspects of drilling systems, machining conditions, and tools are currently available. This paper presents a systematic scheme of drilling damage suppression from the overall drilling system. First, the formation mechanism of damage at different hole positions, including exit push-out delamination, entrance peel-up delamination, and burr and fiber pull-out, is analyzed. Second, the suppression strategies are systematically reviewed from the following four aspects: drilling techniques and methods, drilling conditions, tool design, and multi-techniques integration. The damage evaluation methods are then summarized from qualitative detection and quantitative characterization, covering destructive and nondestructive testing and delamination factors in different dimensions. Finally, the unique advantages of various suppression strategies are determined, and the research gaps and future popular research directions are prospected.
... In the process of mechanical stress modeling, the influence of abrasive particle attitude on the effective abrasive particle number was ignored, thereby, affecting the magnitude of mechanical stress. Moreover, as the theoretical model of residual thermal stress is established on the basis of the model [23] in this paper, the theoretical model ignored the convection heat transfer capacity of air and the residual thermal capacity of cutting fluid on the workpiece [51]. In the model temperature field, the workpiece temperature was slightly higher than the measured temperature, and the thermal stress improved, so more residual tensile stress would affect the results. ...
The special mechanical properties of cemented carbide with high strength and hardness will cause complex stress due to excessive force and heat in the process of precision manufacturing, which will affect precision retention and endurance limit. Given the health and environmental threat of conventional flood cooling and the harsh processing environment of dry grinding, minimum quantity lubrication (MQL) has become an irreplaceable method to machining cemented carbide. However, the addition of nanoparticles changes the force and heat during grinding, which makes the influence on the residual stress of cemented carbide complicated. Therefore, based on the single abrasive grinding force model, the effective abrasive particle number was obtained by simulating the distribution of abrasive particles on the grinding wheel surface, and the mechanical stress model was established, which was loaded onto the workpiece in iterative attenuation mode. The thermal stress model was established based on the temperature field model. The final residual stress prediction model was obtained by determining whether the grinding process yields results and carrying out stress loading and stress relaxation. Experimental verification of the model was carried out under four different grinding conditions of YG8. The minimum friction coefficient of 0.385 was obtained under nanofluid minimum quantity lubrication (NMQL). In the precision analysis of the model, the minimum error value was 5.9% in the direction perpendicular to the feed direction of the workpiece in the dry grinding condition, which proved that the residual stress model had certain reliability.
... These bactericides could inactivate bacteria by destroying the cell membrane of microorganisms, destroying the structure of microbial proteins, and interfering with DNA synthesis [36,37]. The types of bactericides commonly used in the industry include formaldehyde releasers, isothiazolinones, boric acids, and amines [38]. However, these kinds of bactericides are generally irritating and allergenic, and they could not avoid the harm to human health while killing bacteria [39,40]. ...
The application of cutting fluid in the field of engineering manufacturing has a history of hundreds of years, and it plays a vital role in the processing efficiency and surface quality of parts. Among them, water-based cutting fluid accounts for more than 90% of the consumption of cutting fluid. However, long-term recycling of water-based cutting fluid could easily cause deterioration, and the breeding of bacteria could cause the cutting fluid to fail, increase manufacturing costs, and even endanger the health of workers. Traditional bactericides could improve the biological stability of cutting fluids, but they are toxic to the environment and do not conform to the development trend of low-carbon manufacturing. Low-carbon manufacturing is inevitable and the direction of sustainable manufacturing. The use of nanomaterials, transition metal complexes, and physical sterilization methods on the bacterial cell membrane and genetic material could effectively solve this problem. In this article, the mechanism of action of additives and microbial metabolites was first analyzed. Then, the denaturation mechanism of traditional bactericides on the target protein and the effect of sterilization efficiency were summarized. Further, the mechanism of nanomaterials disrupting cell membrane potential was discussed. The effects of lipophilicity and the atomic number of transition metal complexes on cell membrane penetration were also summarized, and the effects of ultraviolet rays and ozone on the destruction of bacterial genetic material were reviewed. In other words, the bactericidal performance, hazard, degradability, and economics of various sterilization methods were comprehensively evaluated, and the potential development direction of improving the biological stability of cutting fluid was proposed.
Surface grinding experiments are conducted on Compacted Graphite Iron (CGI) GJV450 using a resinoid cubic boron nitride (cBN) wheel. The cutting performance of the dry grinding process is compared to emulsifying oil-based fluid, synthetic oil-based fluid, and synthetic oil-based with exfoliated graphite nano-platelets (xGnP) additives. The study also investigates the influence of longitudinal feed on grinding forces, specific energy, force ratio, surface morphology, and surface roughness. The application of all cooling and lubricating fluids leads to a slight reduction of normal and tangential forces. The synthetic oil-based cooling with xGnP nano-platelet only shows a little improvement in cutting force reduction as a result of a relatively low concentration of nano-particles. The ascending of the longitudinal feed generally introduces a higher surface roughness of the CGI workpiece. The roughness under the emulsifying oil-based condition has a higher value, while the cutting with synthetic oil added xGnP exhibits a better surface finish.
The degradation of scaffolds is a critical aspect in tissue engineering and regenerative medicine. Various factors that influence the degradation of scaffold are viscosity, density, hydrophilicity, temperature, cells and degradation environment. In present study, the degradation of scaffold were evaluated in presence of perfused media, Red blood cells (RBC), and cryogenic conditions. Different properties such as density, viscosity and contact angle of bio-ink used for fabrication of scaffold were also evaluated and their correlation to desired environment conditions were also evaluated. A poly electrolyte complex scaffolds (chitosan: alginate, chitosan: gelatine), and explicit scaffolds were considered for degradation study. Explicit scaffold and PEC scaffolds were fabricated form chitosan, alginate and gelatine at mixing ratio of 20:80, 50:50, and 80:20 concentration by solvent casting and etching method. The scaffold degradation studies in perfused media were performed at flow rate of 0.5 ml/min, 1 ml/min and 2 ml/min. The parameters related to degradation of scaffold such as weight and pH of discharge media were also evaluated. Results indicated that degradation of chitosan: alginate at 20:80 concentration had shown maximum degradation in presence of RBCs. Similarly, degradation pattern was equal to linear patten for all the scaffolds except 20:80 and 50:50 concentration of chitosan-alginate in cryogenic conditions. Result of scaffolds degradation in perfused media had shown that scaffolds were degraded maximal at a flow rate of 1 ml/min as compare to other flow rates. Contact angle measurement had proved that all PEC scaffold belongs to the category of hydrophilic family. The scaffold fabricated from higher concentration of chitosan had revealed slower degradation as compare to others configuration. The acceleration of scaffold degradation was tiggered by enzymatic and cellular activities in the presence of RBCs. Perfused media had caused scaffold degradation due to presence of mechanical shear stress.
Nanoparticle-enhanced coolants (NPECs) are increasingly used in minimum quantity lubrication (MQL) machining as a green lubricant to replace conventional cutting fluids to meet the urgent need for carbon emissions and achieve sustainable manufacturing. However, the thermophysical properties of NPEC during processing remain unclear, making it difficult to provide precise guidance and selection principles for industrial applications. Therefore, this paper reviews the action mechanism, processing properties, and future development directions of NPEC. First, the laws of influence of nano-enhanced phases and base fluids on the processing performance are revealed, and the dispersion stabilization mechanism of NPEC in the preparation process is elaborated. Then, the unique molecular structure and physical properties of NPECs are combined to elucidate their unique mechanisms of heat transfer, penetration, and antifriction effects. Furthermore, the effect of NPECs is investigated on the basis of their excellent lubricating and cooling properties by comprehensively and quantitatively evaluating the material removal characteristics during machining in turning, milling, and grinding applications. Results showed that turning of Ti–6Al–4V with multi-walled carbon nanotube NPECs with a volume fraction of 0.2% resulted in a 34% reduction in tool wear, an average decrease in cutting force of 28%, and a 7% decrease in surface roughness Ra , compared with the conventional flood process. Finally, research gaps and future directions for further applications of NPECs in the industry are presented.
Grinding is a crucial process in machining workpieces because it plays a vital role in achieving the desired precision and surface quality. However, a significant technical challenge in grinding is the potential increase in temperature due to high specific energy, which can lead to surface thermal damage. Therefore, ensuring control over the surface integrity of workpieces during grinding becomes a critical concern. This necessitates the development of temperature field models that consider various parameters, such as workpiece materials, grinding wheels, grinding parameters, cooling methods, and media, to guide industrial production. This study thoroughly analyzes and summarizes grinding temperature field models. First, the theory of the grinding temperature field is investigated, classifying it into traditional models based on a continuous belt heat source and those based on a discrete heat source, depending on whether the heat source is uniform and continuous. Through this examination, a more accurate grinding temperature model that closely aligns with practical grinding conditions is derived. Subsequently, various grinding thermal models are summarized, including models for the heat source distribution, energy distribution proportional coefficient, and convective heat transfer coefficient. Through comprehensive research, the most widely recognized, utilized, and accurate model for each category is identified. The application of these grinding thermal models is reviewed, shedding light on the governing laws that dictate the influence of the heat source distribution, heat distribution, and convective heat transfer in the grinding arc zone on the grinding temperature field. Finally, considering the current issues in the field of grinding temperature, potential future research directions are proposed. The aim of this study is to provide theoretical guidance and technical support for predicting workpiece temperature and improving surface integrity.
One-dimensional nanostructures are generally cited as nanowires, nanofibers, nanotubes, and so on. The foremost prominent feature of these materials is their electrical conductivity, which, unlike classical physics, doesn't increase their resistance because the diameter decreases. Numerous properties of these materials like electrical conductivity, optical, magnetic, biological, and environmental their sensory have created many applications for them altogether industries. nanowires (NWs) propose potential impact on electronics, computing, memory, data storage, communications, manufacturing, health, medicine, national security, and other economic sectors as well. NWs offer excellent surface-to-volume ratio (interface phenomena), low defect density, high optical output, and controllable n-type conductivity, making them more appropriate and sensitive for sensing applications. NWs with their ultra-sensitive and real-time detection capabilities lend their applications in nano biosensors, chemical sensors, gas sensors, and electrochemical sensors. NWs have been used in improving the optical absorption as well as for the collection efficacy in photovoltaic devices. NWs having small size, low weight, low cost for mass production, and are also compatible with commercial planar processes for large-scale circuitry. In the paper, the authors are focusing to summarize the recent advances in NWs with their potential applications in various fields such as research, health, security, education, entertainment, and power generation.
Carbon group nanofluids can further improve the friction-reducing and anti-wear properties of minimum quantity lubrication (MQL). However, the formation mechanism of lubrication films generated by carbon group nanofluids on MQL grinding interfaces is not fully revealed due to lack of sufficient evidence. Here, molecular dynamic simulations for the abrasive grain/workpiece interface were conducted under nanofluid MQL, MQL, and dry grinding conditions. Three kinds of carbon group nanoparticles, i.e., nanodiamond (ND), carbon nanotube (CNT), and graphene nanosheet (GN), were taken as representative specimens. The [BMIM]BF4 ionic liquid was used as base fluid. The materials used as workpiece and abrasive grain were the single-crystal Ni-Fe-Cr series of Ni-based alloy and single-crystal cubic boron nitride (CBN), respectively. Tangential grinding force was used to evaluate the lubrication performance under the grinding conditions. The abrasive grain/workpiece contact states under the different grinding conditions were compared to reveal the formation mechanism of the lubrication film. Investigations showed the formation of a boundary lubrication film on the abrasive grain/workpiece interface under the MQL condition, with the ionic liquid molecules absorbing in the groove-like fractures on the grain wear’s flat face. The boundary lubrication film underwent a friction-reducing effect by reducing the abrasive grain/workpiece contact area. Under the nanofluid MQL condition, the carbon group nanoparticles further enhanced the tribological performance of the MQL technique that had benefited from their corresponding tribological behaviors on the abrasive grain/workpiece interface. The behaviors involved the rolling effect of ND, the rolling and sliding effects of CNT, and the interlayer shear effect of GN. Compared with the findings under the MQL condition, the tangential grinding forces could be further reduced by 8.5%, 12.0%, and 14.1% under the diamond, CNT, and graphene nanofluid MQL conditions, respectively.
Surface integrity is an important term that describes the surface behaviour of a ground component. Grinding is defined as a finishing operation that has high specific energy consumption. High heat generation while grinding, adversely affects the surface integrity of the ground surfaces. With the development of advanced materials such as superalloys, this process is widely used in bulk machining for making critical components used in dynamic loading. Therefore, it becomes necessary to investigate the surface integrity of the ground components, as their surface integrity primarily determines their performance and durability. The purpose of this work is to enhance the grinding performance of Inconel 718, a difficult-to-grind material, by employing silver and zinc oxide (ZnO)-based ecological nanofluids in a minimum quantity lubrication (MQL) mode. The grinding parameters such as wheel speed and table speed are kept constant with variations in the grinding infeed. The grinding performance in terms of grinding forces, apparent coefficient of friction, surface roughness and residual stresses on the ground surfaces have been investigated. Skewness, kurtosis and the Abbott–Firestone curve have also been analysed using two-dimensional and three-dimensional plots for an in-depth study of ground surface behaviour. The finding suggests that ZnO-based nanofluid outclass the silver-based nanofluid using MQL mode in terms of reduced grinding forces and favourable residual stress. Therefore, it appears as the potential grinding environment for the improved grinding performance of Inconel 718.
Grinding is one of the most complex techniques of removing material from parts by the countless number of hard and sharp abrasive grains. Grinding creates a substantial amount of heat, which causes surface or subsurface damage, thermal damage, change in the metallographic structure of the material surface. In order to lesson these phenomena, cutting fluids are frequently used in the grinding zone. Minimum Quantity Lubrication (MQL) was suggested as a cost-effective and environmentally friendly lubrication for reducing heat and the expenses of grinding fluid. Despite the fact that MQL plays a crucial role in increasing machining performance, reviews on its use in high-speed machining are conflicted. This review article examines some of the most frequent nanofluids used in MQL systems during grinding processes. Nanofluids in MQL technique are a cutting-edge and eco-friendly approach that substitutes both traditional MQL and flood coolant in the grinding process. The effects of nanofluids on workpiece surface roughness, tangential force, coefficient of friction, G-ratio, grinding specific energy, wheel wear, grinding temperature, workpiece hardness and residual stress are thoroughly discussed and the findings were compared. After reading this review article, one may quickly gain an overview of existing research in the fields of nanofluids. Finally, this study looks at the thermo-physical characteristics of different nanofluids such as contact angle, thermal conductivity, and viscosity.
A high grinding temperature will cause thermal damage to a workpiece surface and deterioration of surface integrity, which is the bottleneck of grinding. The present grinding temperature theoretical model is based on grain homogeneity and the continuous heat source distribution in the grinding zone. However, the random change in interference between the effective grains and a workpiece during the machining process causes a change in the grain tribological properties, resulting in varying transient grinding temperatures. Based on the current situation, the grain tribological mechanism and an improved temperature model based on a discrete heat source are proposed to reveal the temperature variation law of a workpiece in an actual grinding process. First, the surface topography model of a grinding wheel is established based on the geometric characteristics of grains, and the determination mechanism of effective grains is revealed. Furthermore, the interference mechanical behavior of the grains and workpiece is analyzed according to the kinematic law of grains in the sliding, plowing, and cutting stages. The mechanical model and specific grinding energy model at different stages are established, and the thermal distribution mechanism of effective grains is revealed. Finally, a temperature field mathematical model of a discrete heat source is established, and numerical simulation is performed to demonstrate the dynamic temperature change process of different grains. A new experimental method for measuring temperature at different positions of the workpiece with a bipolar thermocouple array is designed, and a regional numerical simulation and experimental temperature comparison method is innovatively proposed. Experimental results show that the grinding temperature measured under different cutting depth conditions is in good agreement with the numerical results, and the variation law is consistent. The minimum error in 64 groups of experimental measuring and numerical calculation comparison zones can reach 4.9%, and the proportion of zones with errors less than 10% can approach 86%. This study will provide a theoretical basis for the accurate suppression of workpiece surface thermal damage and the development of precision grinding in engineering discipline and machinery industry.
The substitution of biolubricant for mineral cutting fluids in aerospace material grinding is an inevitable development direction, under the requirements of the worldwide carbon emission strategy. However, serious tool wear and workpiece damage in difficult-to-machine material grinding challenges the availability of using biolubricants via minimum quantity lubrication. The primary cause for this condition is the unknown and complex influencing mechanisms of the biolubricant physicochemical properties on grindability. In this review, a comparative assessment of grindability is performed using titanium alloy, nickel-based alloy, and high-strength steel. Firstly, this work considers the physicochemical properties as the main factors, and the antifriction and heat dissipation behaviours of biolubricant in a high temperature and pressure interface are comprehensively analysed. Secondly, the comparative assessment of force, temperature, wheel wear and workpiece surface for titanium alloy, nickel-based alloy, and high-strength steel confirms that biolubricant is a potential replacement of traditional cutting fluids because of its improved lubrication and cooling performance. High-viscosity biolubricant and nano-enhancers with high thermal conductivity are recommended for titanium alloy to solve the burn puzzle of the workpiece. Biolubricant with high viscosity and high fatty acid saturation characteristics should be used to overcome the bottleneck of wheel wear and nickel-based alloy surface burn. The nano-enhancers with high hardness and spherical characteristics are better choices. Furthermore, a different option is available for high-strength steel grinding, which needs low-viscosity biolubricant to address the debris breaking difficulty and wheel clogging. Finally, the current challenges and potential methods are proposed to promote the application of biolubricant.
Carbon fiber reinforced polymer (CFRP)/titanium alloy (Ti) stacks have promising application in aerospace field due to their excellent mechanical properties. During integrated drilling of CFRP/Ti stacks, the machining process at interface between CFRP and titanium alloy is very complicated. The interaction among CFRP, titanium alloy and cutting tool leads to poor processing quality, serious tool wear and other problems. In this paper, in order to deeply analyze the influence mechanism of interface area on the machining process, the research achievements and progress of drilling CFRP/Ti stacks are reviewed. Special attention is paid to the machining characteristics and CFRP damage mechanism at stack interface during drilling and helical milling of CFRP/Ti stacks. The cutting force characteristics, temperature characteristics and tool wear characteristics of interface machining are analyzed, and the damage mechanism and evaluation method are summarized. In order to solve the existing problems in drilling CFRP/Ti stacks, the suppression strategies of interface damage in recent years are discussed from four aspects: machining parameters, machining environment, tool structure and advanced machining technology. The research trend of laminated interface machining is prospected, which provides an important reference value for the realization of precision, high efficiency and low damage integrated drilling of CFRP/Ti stacks.
Metal cutting fluids (MCFs) under flood conditions do not meet the urgent needs of reducing carbon emission. Biolubricant-based minimum quantity lubrication (MQL) is an effective alternative to flood lubrication. However, pneumatic atomization MQL has poor atomization properties, which is detrimental to occupational health. Therefore, electrostatic atomization MQL requires preliminary exploratory studies. However, systematic reviews are lacking in terms of capturing the current research status and development direction of this technology. This study aims to provide a comprehensive review and critical assessment of the existing understanding of electrostatic atomization MQL. This research can be used by scientists to gain insights into the action mechanism, theoretical basis, machining performance, and development direction of this technology. First, the critical equipment, eco-friendly atomization media (biolubricants), and empowering mechanisms of electrostatic atomization MQL are presented. Second, the advanced lubrication and heat transfer mechanisms of biolubricants are revealed by quantitatively comparing MQL with MCF-based wet machining. Third, the distinctive wetting and infiltration mechanisms of electrostatic atomization MQL, combined with its unique empowering mechanism and atomization method, are compared with those of pneumatic atomization MQL. Previous experiments have shown that electrostatic atomization MQL can reduce tool wear by 42.4% in metal cutting and improve the machined surface R a by 47% compared with pneumatic atomization MQL. Finally, future development directions, including the improvement of the coordination parameters and equipment integration aspects, are proposed.
Cutting fluid plays a cooling-lubrication role in the cutting of metal materials. However, the substantial usage of cutting fluid in traditional flood machining seriously pollutes the environment and threatens the health of workers. Environmental machining technologies, such as dry cutting, minimum quantity lubrication (MQL), and cryogenic cooling technology, have been used as substitute for flood machining. However, the insufficient cooling capacity of MQL with normal-temperature compressed gas and the lack of lubricating performance of cryogenic cooling technology limit their industrial application. The technical bottleneck of mechanical—thermal damage of difficult-to-cut materials in aerospace and other fields can be solved by combining cryogenic medium and MQL. The latest progress of cryogenic minimum quantity lubrication (CMQL) technology is reviewed in this paper, and the key scientific issues in the research achievements of CMQL are clarified. First, the application forms and process characteristics of CMQL devices in turning, milling, and grinding are systematically summarized from traditional settings to innovative design. Second, the cooling-lubrication mechanism of CMQL and its influence mechanism on material hardness, cutting force, tool wear, and workpiece surface quality in cutting are extensively revealed. The effects of CMQL are systematically analyzed based on its mechanism and application form. Results show that the application effect of CMQL is better than that of cryogenic technology or MQL alone. Finally, the prospect, which provides basis and support for engineering application and development of CMQL technology, is introduced considering the limitations of CMQL.
Grinding is a manufacturing process which significantly contributes in producing high precision and durable components required in numerous applications such as aerospace, defence and automobiles. This review article is focused to uncover history, witness the present and predict the future of the grinding process. While going through the literature, it has been observed that minimal work has been done in explaining the history, present status and future scopes of the grinding process. In this era of information and environmental awareness, sustainability aspects have become a primary concern of almost every research field. In the grinding process too, the research work includes ecological elements such as reducing the consumption of cutting fluids through minimum quantity lubrication, utilizing cryogenics, hybrid lubrication and cooling techniques that are still required to be explored critically. Further, some significant findings of the prevailing research in grinding include modification in grinding wheel surface, merging different grinding principles such as usages of the textured grinding wheel, ultrasonic grinding, 3D printing of grinding wheel and artificial intelligence in grinding are also presented. Another unascertained problem is the management of grinding swarf, which is being attended to by recycling it to fabricate composites which is expected to be another prominent domain of research. Further, the advancements taking place exhibit the potential of the grinding process, suggesting that its future is bright and ever-growing.
The conventional flood i.e., mineral-based cutting fluid approach was extensively utilized on the shop floor to diminish the amount of friction and power consumption while precision grinding of “difficult-to-machine” materials like hardened AISI H13 tool steel. The excessive exposure and usage of conventional fluids lead to severe environmental threats like air and water pollution, and unfavourable impacts on operator health. Therefore, sustainable manufacturing in terms of minimum quantity lubrication (MQL) grinding is major concert in modern tooling industries including technological, economical, and environmental aspects. The objective of present study is to identify the impact of six different eco-friendly nano-lubricants i.e., castor oil (CO), soybean oil (SO), castor oil-deionized water (CO + DIW) emulsion, soybean oil-deionized water (SO + DIW) emulsion, Al2O3 nanofluids (NFs): 0.5 wt%, and Al2O3 NFs: 1 wt% on grindability and surface integrity indices, energy consumption, carbon emission, and production cost while MQL grinding of AISI H13 tool steel. The lubrication mechanism and its characteristics were studied by biodegradation rate, pH and sedimentation test, thermal conductivity, viscosity, surface tension, and wettability. The grindability indices, namely, apparent friction coefficient, surface roughness (Rɑ and Rz value), bearing area (BC) ratio, surface topography, and microchip morphology were evaluated and analyzed. The results suggest that the downfeed and Al2O3 NFs have the greatest impact on technological, economical, and environmental aspects of MQL grinding. It is found that the extensive cooling and lubricating performance of Al2O3 NFs was superior to that of biodegradable emulsion, and straight vegetable oil offered the optimal results under all lubrication evaluation tests. Also, significant improvement in grindability performance was obtained with Al2O3 NFs: 1 wt% owing to strong anti-friction lubricating tribo-film, and higher boiling heat transfer through effective rolling and mending effect. The grindability enhancement rates of apparent friction coefficient, Rɑ, Rz, and BC ratio are 28.48%, 59.66%, 50.18%, and 6.25%, respectively at 32 μm downfeed as followed by SO + DIW emulsion. Furthermore, poor ground surface quality along with spherical and sharp wear tracks on microchips was indicated with SO + DIW emulsion. According to sustainable aspects, Al2O3 NFs: 1 wt% outperformed straight vegetable oil in terms of lower energy consumption (17.06 kJ), carbon emission (00468 kgCO2), and production cost (0.255 $), which were 15.10%, 26.76%, and 13.55% lower than soybean oil. It is confirmed that Al2O3 NFs is the best substitute for the straight vegetable oil and vegetable oil-deionized water emulsion for robust sustainable manufacturing of tooling components.
The application of cutting fluid is the most direct and effective method for improving the productivity in machining difficult-to-cut materials. Besides the typical flood cooling method, advanced and eco-friendly solutions such as minimum quantity lubrication (MQL) and cryogenic minimum quantity lubrication (CMQL) have been applied in green manufacturing processes to avoid the environmental and health issues associated with conventional cutting fluid. High-efficiency machining of thin-wall components is of significant importance to the aerospace and defence industries. However, the effects of CMQL in the thin-wall milling process have not been investigated, and the mechanisms of tool wear, chip evolution, stress distribution and part deformation are still unclear. To address this gap, this paper presents the investigation and corresponding analysis of CMQL in the machining of titanium thin-wall components. Comparative experiments were carried out under different cutting environments, including flood cooling, MQL and CMQL machining. The tool wear state, cutting force, chip morphology, surface quality and workpiece deformation were compared and analysed. Experimental results show that CMQL machining can significantly lower the cutting loads and deformation values of thin-wall parts, especially at higher spindle speed. Compared with flood and MQL machining, CMQL machining led to approximate 28.5% and 31.2% smaller cutting force at the spindle speed of 4500 rpm, and the maximum deformation in CMQL machining was decreased by 41.4% and 44.7%, respectively. Meanwhile, the wear resistance of the cutting tool and surface quality is enhanced in comparison with flood cooling and MQL machining. It was shown that the machined surface under CMQL condition exhibited 34.5% and 45.8% lower surface roughness (Ra) compared to flood and MQL machining at the highest spindle speed. Overall, the experimental outcomes demonstrate the feasibility of CMQL in improving the machinability of thin-wall components made from difficult-to-cut material, owing to its superior lubrication and cooling functions. The cryogenic cooling action and induced thermal effect are especially beneficial to controlling the flexible deformation.
Hybrid nanofluids are characterized as dilution of hybrid nanoparticles in the base fluids. The hybrid nanoparticles may comprise two or more nanoparticles. The investigation effort toward the applicability of hybrid nanofluids in various equipment is increasing gradually because of its synergistic properties. This chapter outlines hybrid nanofluids’ hydrothermal properties, demonstrating that they possess higher heat transfer rates over the single nanoparticle-based nanofluids. Properties like surface tension, pumping power, pressure drop, friction factor, and fouling factor are discussed. Surface tension, friction factor, pressure drop, and pumping power are augmented with higher particle loadings. Increased fouling factor indicates a reduction in heat transfer coefficient with the use of hybrid nanofluids. Recent challenges are presented and reported that further investigation is required to study various types of hybrid nanoparticles, the stability of the nanofluid, thermophysical properties, heat transfer, less friction factor, pumping power, and pressure drop characteristics.
A novel type of nanofluid, known as the hybrid nanofluid, is prepared by suspending different kinds of nanoparticles (more than one) or hybrid (composite) nanoparticles in the pure fluid to produce a colloidal suspension. The chemical and physical features of different materials are combined in the hybrid material simultaneously, providing the characteristics in a homogeneous phase. The effective viscosity and density of hybrid nanofluids may be in the same order for mononanofluids, while their thermal conductivity might be substantially higher than mono nanofluids considering synergistic effects. The outstanding enhancement in thermal transfer properties of nanofluids led researchers to use them in various engineering applications, including nuclear cooling, desalination, machining, refrigeration, engine cooling, heat exchangers (HEX), solar collectors, and electronics cooling. This chapter gives a brief overview of the applications of hybrid nanofluids and the challenges associated with them, as well as the way forward for research gaps that still need attention.
Carbon fiber-reinforced polymer (CFRP) easily realizes the integrated manufacturing of components with high specific strength and stiffness, and it has become the preferred material in the aerospace field. Grinding is the key approach to realize precision parts and matching the positioning surface for assembly and precision. Hygroscopicity limits the application of flood lubrication in CFRP grinding, and dry grinding leads to large force, surface deterioration, and wheel clogging. To solve the above technical bottleneck, this study explored the grindability and frictional behavior of CNT biological lubricant MQL through grinding experiments and friction-wear tests. Results showed that the CNT biological lubricant reduced the friction coefficient by 53.47% compared with dry condition, showing optimal and durable antifriction characteristics. The new lubrication was beneficial to suppressing the removal of multifiber block debris, tensile fracture, and tensile-shear fracture, with the advantages of tribological properties and material removal behavior, the tangential and normal grinding force, and the specific grinding energy were reduced by 40.41%, 31.46%, and 55.78%, respectively, compared with dry grinding. The proposed method reduced surface roughness and obtained the optimal surface morphology by preventing burrs, fiber pull-out, and resin smearing, and wheel clogging was prevented by temperature reduction and lubricating oil film formation. S a and S q of the CNT biological lubricant were reduced by 8.4% and 7.9%, respectively, compared with dry grinding. This study provides a practical basis for further application of CNT biological lubricant in CFRP grinding.
In nanofluid minimum quantity lubrication (NMQL) milling of aviation aluminum alloy, it is the bottleneck problem to adjust the position parameters (target distance, incidence angle, and elevation angle) of the nozzle to improve the surface roughness of milling, which has large and uncontrollable errors. In this paper, the influence law of milling cutter speed, helical angle, and cavity shape on the flow field around the milling cutter was studied, and the optimal nozzle profile parameters were obtained. Using 7050 aluminum alloy as the workpiece material, the milling experiment of the NMQL cavity was conducted by utilizing cottonseed oil-based Al2O3 nanofluid. Results show that the high velocity of the surrounding air flow field and the strong gas barrier could be attributed to high rotating velocities of the milling cutter. The incidence angle of the nozzle was consistent with the helical angle of the milling cutter, the target distance was appropriate at 25–30 mm, and the elevation angle was suitable at 60°–65°. The range and variance analyses of the signal-to-noise ratio of milling force and roughness were performed, and the chip morphology was observed and analyzed. The results show that the optimal combination of nozzle position parameters was the target distance of 30 mm, the incidence angle of 35°, and the elevation angle of 60°. Among these parameters, target distance had the largest impact on cutting performance with a contribution rate of more than 55%, followed by incidence angle and elevation contribution rate. Analysis by orthogonal experiment revealed that the nozzle position parameters were appropriate, and Ra (0.087 μm) was reduced by 30.4% from the maximum value (0.125 μm). Moreover, Rsm (0.05 mm) was minimum, which was 36% lower than that of the seventh group (Rsm = 0.078 mm).
Owing to superior physio-chemical characteristics, titanium alloys are widely adopted in numerous fields such as medical, aerospace and military applications. However, titanium alloys have poor machinability due to its low thermal conductivity which results in high temperature during machining. Numerous lubrication and cooling techniques have already been employed to reduce the harmful environmental footprints, temperature elevation, and to improve the machining of titanium alloys. In this current work, an attempt has been made to evaluate the effectiveness of two cooling and lubrication techniques namely cryogenic cooling and hybrid nano-additives based minimum quantity lubrication (MQL). The key objective of this experimental research is to compare the influence of cryogenic CO2 and hybrid nanofluid based MQL techniques for turning Ti-6Al-4V. The used hybrid nano-fluid is Alumina (Al2O3) with Multi-walled carbon nanotubes (MWCNTs) dispersed in vegetable oil. Taguchi based L9 orthogonal-array was used for the design of the experiment. The design variables were cutting speed, feed rate, and cooling technique. Results showed that the hybrid nano-additives reduced the average surface roughness by 8.72%, cutting force by 11.8%, and increased the tool life by 23% in comparison with the cryogenic cooling. Nevertheless, the cryogenic technique showed a reduction of 11.2% in cutting temperature compared to the MQL-hybrid nano-fluids at low and high levels of cutting speed and feed rate. In this regard, a milestone has been achieved by implementing two different sustainable cooling/lubrication techniques.
The removal of material in the ductile regime while improving machining efficiency is currently the technical bottleneck in grinding zirconia ceramics. Prediction models of minimum chip thickness (hmin) and ductile–brittle transition chip thickness (hd–b) were developed according to grinding mechanism. Results showed that both hmin and hd–b decreased with increasing friction coefficient. Grinding experiments were carried out using the maximum undeformed chip thickness as the input parameter. Experimental results showed that the hmin value in dry grinding is 0.24 μm. Meanwhile, the hmin values under minimum quantity lubrication (MQL) and nanoparticle jet MQL (0.4, 0.8, 1.2, 1.6, and 2 vol.%) are 0.27, 0.34, 0.49, 0.65, 0.76, and 0.91 μm, respectively. Furthermore, the hd–b value in dry grinding is 0.8 μm, and the hd–b values under lubrication condition that corresponds to hmin are 1.79, 1.98, 2.15, 2.27, 2.39, and 2.59 μm, respectively. The experimental results show the same trend as that of the prediction model. The theoretical calculation is basically consistent with the measured values, with model errors of 7.9% and 6.3%, thereby verifying the accuracy of the chip thickness models.
Nanofluid minimum quantity lubrication (NMQL) technique has many technological and economic advantages in grinding operation. NMQL can improve grinding performance in terms of cooling and lubrication and is ecofriendly because it consumes a small amount of grinding fluid. Ultrasonic machining can improve grinding performance owing to its reciprocating vibration mechanism and furrow widening. Consequently, the simultaneous utilization of these techniques is anticipated to improve the surface quality, especially for hard brittle materials. In this research, multiangle two-dimensional (2D) ultrasonic vibration is utilized in zirconia ceramic grinding. Results reveal that the adhesion and material peeling phenomenon on the workpiece surface is obviously reduced compared with dry grinding without ultrasonic vibration. The synergistic effect of multiangle 2D ultrasonic and NMQL is also studied. With increased angle, the roughness value is found to initially increase (from 45° to 90°) and then decreases (from 90° to 135°). Moreover, the lubricating effect under 90° is the poorest, with the highest Ra and RSm values of 0.703 μm and 0.106 mm, respectively; conversely, the minimum Ra value (0.585 μm) is obtained under 45°, and the lowest RSm value (0.076 mm) is obtained under 135°.
Difficult-to-cut materials have been widely employed in many engineering applications, including automotive and aeronautical designs because of their effective properties. However, other characteristics; for example, high hardness and low thermal conductivity has negatively affected the induced surface quality and tool life, and consequently the overall machinability of such materials. Inconel 718, is widely used in many industries including aerospace; however, the high temperature generated during machining is negatively affecting its machinability. Flood cooling is a commonly used remedy to improve machinability problems; however, government regulation has called for further alternatives to reduce the environmental and health impacts of flood cooling. This work aimed to investigate the influence of dispersed multi-wall carbon nanotubes (MWCNTs) and aluminum oxide (Al2O3) gamma nanoparticles, on enhancing the minimum quantity lubrication (MQL) technique cooling and lubrication capabilities during turning of Inconel 718. Machining tests were conducted, the generated surfaces were examined, and the energy consumption data were recorded. The study was conducted under different design variables including cutting speed, percentage of added nano-additives (wt.%), and feed velocity. The study revealed that the nano-fluids usage, generally improved the machining performance when cutting Inconel 718. In addition, it was shown that the nanotubes additives provided better improvements than Al2O3 nanoparticles.
Considering the poor lubricating effect of cryogenic air (CA) and inadequate cooling ability of nanofluid minimum quantity lubrication (NMQL), this work proposes a new manufacturing technique cryogenic air nanofluid minimum quantity lubrication (CNMQL). A heat transfer coefficient and a finite difference model under different grinding conditions were established based on the theory of boiling heat transfer and conduction. The temperature field in the grinding zone under different cooling conditions was simulated. Results showed that CNMQL exerts the optimal cooling effect, followed by CA and NMQL. On the basis of model simulation, experimental verification of the surface grinding temperature field under cooling conditions of CA, MQL, and CNMQL was conducted with Ti–6Al–4V as the workpiece material. Simultaneously, CNMQL exhibits the smallest specific tangential and normal grinding forces (2.17 and 2.66 N/mm, respectively). Further, the lowest grinding temperature (155.9 °C) was also obtained, which verified the excellent cooling and heat transfer capabilities of CNMQL grinding. Furthermore, the experimental results were in agreement with theoretical analysis, thereby validating the accuracy of the theoretical model.
Efficient application of minimum quantity lubrication (MQL) in grinding is not only related to grinding conditions and delivery parameters but also affected by spraying atomization characteristics. In this study, a double-outlet nozzle is proposed and the flow field of the MQL grinding is investigated by two-stage atomization model. The side-mixing structure of double-outlet nozzle indicates that the grinding fluid is atomized at the windward side and the flow rate of grinding fluid for a single radial hole is smaller than that for the liquid pipe. Therefore, more excellent atomization performances, in terms of liquid droplet size, uniformity, and velocity of the liquid droplets, are obtained for double-outlet nozzle in comparison with single-outlet nozzle. The liquid droplets sprayed from auxiliary outlet of double-outlet nozzle impact on the grinding wheel and change the airflow direction around the grinding wheel. Thus, the air barrier around the grinding wheel is disturbed and the liquid droplets sprayed from main outlet can be injected into the grinding zone easily. Experimental results indicate that two-stage atomization model is reliable.
This paper investigated the effect of nanofluid MQL with vegetable-based oil and ester oil as base fluids on cutting force and temperature in cylindrical turning of AISI 1045 medium carbon steel. Comparative experiments were carried out under different cooling/lubrication conditions, i.e., dry cutting, minimal quantity lubrication (MQL) with LB2000 vegetable-based oil, MQL with PriEco6000 unsaturated polyol ester, graphite-LB2000 nanofluid MQL, and graphite-PriEco6000 nanofluid MQL. For this research, graphite-LB2000 and graphite-PriEco6000 nanofluids were prepared by a two-step method, and their thermophysical properties such as viscosity, surface tension, wettability, and thermal conductivity were measured. The experimental results show that application of graphite oil-based nanofluid MQL reduced the cutting force and temperature significantly. Furthermore, graphite-LB2000 nanofluid MQL showed better performance than graphite-PriEco6000 nanofluid MQL in terms of reduction in cutting force and temperature, especially at a high cutting speed. Therefore, compared with PriEco6000 unsaturated polyol ester, LB2000 vegetable-based oil was optimal base oil for graphite oil-based nanofluid MQL machining.
New experimental data are reported for water based nanofluids to enhance the heat transfer performance of a car radiator. ZnO nanoparticles have been added into base fluid in different volumetric concentrations (0.01%, 0.08%, 0.2% and 0.3%). The effect of these volumetric concentrations on the heat transfer performance for car radiator is determined experimentally. Fluid flow rate has been varied in a range of 7–11 LPM (liter per minute) (corresponding Reynolds number range was 17,500–27,600). Nanofluids showed heat transfer enhancement compared to the base fluid for all concentrations tested. The best heat transfer enhancement up to 46% was found compared to base fluid at 0.2% volumetric concentration. A further increase in volumetric concentration to 0.3% has shown a decrease in heat transfer enhancement compared to 0.2% volumetric concentration. Fluid inlet temperature was kept in a range of 45–55 °C. An increase in fluid inlet temperature from 45 °C to 55 °C showed increase in heat transfer rate up to 4%.
Cryogenic machining of porous tungsten is an effective method to achieve as-machined porous surfaces. Dispenser cathodes, which are high performance electron emitting devices, rely on the (surface) porosity of porous tungsten for their functionality. Conventional (dry, flood, MQL) machining results in unwanted smearing of surface pores and requires the use of a plastic infiltrant to stabilize pores during machining. Previous studies have shown the ability of PCD tools to achieve controlled micro-fracture which occurs only at low cutting speeds (vc∼10-20 m/min) along with cryogenic cooling. This study investigates the influence of cryogenic pre-cooling time and depth of cut on the attainable surface morphology of porous tungsten. Negative rake cermet tool inserts were used to demonstrate the ability of non-diamond tools to achieve similar results. Three cryogenic pre-cooling times (60, 120 and 180s) are compared to establish their relative effectiveness in enabling the infiltrant-free cryogenic machining of porous tungsten with the objective of achieving maximum surface porosity. It is found that increased pre-cooling time increases the as- machined surface porosity and significantly alters the deformation mechanism during machining. Lastly, a qualitative relationship between the chips generated during the cryogenic machining and as-machined surface porosity is laid out.
Nanofluids, suspensions of nanoparticles in base fluid, has shown attractive cooling and lubricating properties. The nano-coolants and nano-lubricants find applications in a wide variety of materials processing technologies. It is anticipated that, if properly employed, nanofluids usage could surpass the conventional cutting fluids in the future. Minimum quantity lubrication (MQL) technique also, has achieved a significant consideration in manufacturing processes to minimise the environmental loads caused by the usage of traditional cutting fluids. The aim of this work is to examine the potential of Al2O3 nanofluid under MQL mode to improve the grinding characteristics of Ti-6Al-4V alloy. 1% Volume concentration of water-based Al2O3 nanofluid was applied during the surface grinding operation using an indigenously developed MQL setup and the results have been compared with those of conventional coolant under both flood cooling and MQL mode.
Gear hobbing in cryogenic air with minimal quantity lubricant (MQL) is a better choice to take place of traditional gear hobbing in oily cutting fluid, in which cryogenic air with pulverized vegetable oil place the great amount of mineral cooling oil, to play the role of lubrication, cooling, chip clearance, and rust prevention. By the comparative experiments, differences on cutter wear are explored, among cryogenic gear hobbing with MQL, gear hobbing in oily cutting fluid, and dry gear hobbing. It indicates that the gear hobbing in cryogenic air with minimal quantity lubricant is practical, and not only a great amount of cooling oil is saved to lower cost and environment pollution, but also life-saving of hobbing cutter reduces production cost.
This paper details an investigation into the performance of PVD tungsten carbide coated ball nose milling inserts when conducting high-speed cutting of Inconel 718 under eco-friendly machining methods of cryogenic carbon dioxide (CO2) and dry cutting conditions. The experiments were performed at varying cutting parameters of; cutting speed: 120–140 m/min, feed rate: 0.15–0.25 mm/tooth, and axial depth of cut: 0.3–0.7 mm. The radial depth of cut was kept constant at 0.4 mm. A new cryogenic CO2 cooling system was introduced for efficient and consistent cooling performance during cutting. The analysis includes the tool life, tool wear patterns and mechanisms as well as its relationship with the chips’ morphology. The experimental results showed that cryogenic and dry cutting conditions reported approximately similar tool wear patterns. The tool wear started with smooth abrasion and chipping around the depth of cut line, which then progressed into flank wear and finally notching and flaking via mechanisms of abrasive and adhesive wears. However, severe BUE was repeatedly observed under dry cutting, which widened the flaking and accelerated the notching. Hence, cryogenic CO2 showed significant improvement towards increasing the tool life to a maximum of 70.8% relative to dry cutting. The consistent cooling effect by the cryogenic CO2 managed to efficiently reduce the cutting temperature at the cutting point to 80% compared to dry cutting, which is believed to be the main factor causing the aforementioned improvement. The strong influence of cutting conditions and tool wear patterns upon the chip morphology was also evident. Compared to cryogenic cutting, the shape and colour of the chips were found to be severe, distorted, and darker in dry cutting, which confirmed that it was thermally affected by the high cutting temperature.
Nanofluid minimum quantity lubrication (NMQL) is an emerging cleaner and sustainable technique. However, the effective immersion of nanofluids in the grinding zone in NMQL grinding limits the extensive application of this technique. Ultrasonic vibration can exert a pumping effect that injects nanofluids into the interface between the grinding wheel and workpiece. Furthermore, technique integration benefits the infiltration state transition of micro-droplets. However, evaluation of the coupling effect and surface morphology of multi-angle 2D ultrasonic vibration integrated with NMQL has rarely been performed. This study aims to address these research limitations. A kinematics model was developed, and the grain and workpiece relative motion trails in 2D ultrasonic vibration-assisted grinding (UVAG) were simulated at different resultant vibration angles (θ). The grain’s cutting characteristics were then analyzed and found to be conducive to the full infiltration of nanofluids into the grinding zone. Moreover, the surface characterization of multi-angle 2D UVAG coupled with NMQL was evaluated experimentally. Results showed that the optimal θ was achieved at 45° due to the differential cutting action of the follow-up grain. NMQL obtained a better result than flooding at the same θ. When the gain effect of the coupling techniques was reflected in surface roughness, the Ra value decreased by 19.5 % (compared with UVAG) and 39.9 % (compared with NMQL). The autocorrelation function curves presented periodic and continuous local oscillations under the grinding conditions of 2D UVAG with θ = 45° and θ = 135°.
To address the current bottleneck of debris formation mechanism in plastic removal for hard-brittle materials, a minimum chip thickness (h min ) model that considers lubrication conditions (represented by frictional angle β) is developed according to strain gradient, as well as geometry and kinematics analyses. Model results show that h min decreases with increasing β. Furthermore, grinding experiments using single diamond grain under different lubricating conditions are carried out to verify the model. With increasing β, h min values are 71.6, 57.8, 52.0, 50.7, 45.6, 39.7, and 32.4 nm, thereby verifying the trend of h min decreasing with increasing β. Furthermore, the location of size effect occurs is determined according to the variation trend of single abrasive particle specific energy and unit grinding force curves. The size effect occurs in the border area of ploughing, the cutting region, and mainly, in the ploughing region. Theoretical analysis results are consistent with experimental results with a model error of 6.06%, thereby confirming the validity of the theoretical model.
The objective of compiling this study is to seek the attention of young scholars and experts working in the field of heat transfer by discussing the applications and challenges of hybrid nanofluids with a concise discussion on its history, synthesis techniques, thermophysical properties, research gaps, future directions, current status, and the leading groups, organizations, and countries around the world. Applications in different fields like solar energy, heat pipes, automotive industry, manufacturing industry, heat exchangers, cooling of electronic equipment's etc. have been reviewed and discussed in this study. Nanofluids are part of these inventions that possess the ability of uprising the field of heat transfer, but instead of its superior thermal, electrical, and optical properties, advancement in the form of hybrid nanofluids and a numerous study conducted around the world, investigators and manufacturers are still facing the problem of practicing nanofluids in heat transfer devices used commercially and even in an individual's life. This problem works like a magnet, capturing the attention of research societies working around the world by inspiring them to take control and lead this field to the destination of domestic and commercial implementation. With the help of this article, authors endeavored to identify some important work orientations and existing problems that interrupted its performance and implementation for the convenience of captivated scholars. The most recent research work has improved the thermophysical properties of nanofluids by introducing hybrid nanofluids, working on preparation techniques, and by adding the surfactants to improve its stability but still need a lot of attention for the development of correlations/models that can predict the thermophysical properties and heat transfer characteristics, to make it cost-effective, improve its stability, and finally its implementation.
Titanium alloys are generally known as difficult-to-machine materials because of their low machinability ratings. Their usage is favored for demanding sectors because of their high strength to weight ratio, high corrosion resistance and ability to operate at elevated temperatures. Machining of titanium alloys results in higher environmental burden, because they require high energy and generous amount of cutting fluids during machining. It is a well-known fact that most of the cutting fluids are toxic and non-biodegradable in nature and their disposal is costly. Therefore, researchers in metal cutting are keen to explore the potential of minimum quantity lubrication (MQL) and minimum quantity cooling lubrication (MQCL) based cooling techniques as an alternate to conventional flood cooling. When MQL and MQCL techniques are used by employing biodegradable vegetable based oils then there is an encouraging potential of replacing the non-biodegradable cutting fluids. This study documents the recent experimental and numerical advances achieved in the MQL and MQCL assisted techniques for machining titanium alloys. The study also highlights the current challenges in this area and recommends future work to address these challenges.
Excessively high temperature is currently the technical bottleneck in clinical neurosurgery bone grinding, while nanoparticle jet mist cooling (NJMC) is an effective solution to prevent heat injuries. Undeformed chip thickness model and heat flux model are established, and convective heat transfer coefficient model under NJMC condition is established by using mathematical statistics method. Results show that bone surface temperature decreases with the increase of nanoparticle volume fraction. The mechanical properties of bovine femur compact bone are most similar to human bone, which is used in the micro grinding experiment. Results found that, compare with mist cooling (32.7℃), temperature using 0.5%, 1%, 1.5%, 2%, 2.5% nanofluids is 14.1%, 17.1%, 19.6%, 22.9% and 33.3% lower, verifying the law of surface temperature decreases with the increase of nanoparticle volume fraction. The theoretical analysis is in good agreement with experimental results, confirming the validity of the theoretical model. Mechanical machining techniques are applied to healthcare, aiming to provide an effective way to lower micro-grinding temperature in clinical neurosurgery.
CNTs are commonly used nanoparticles in NMQL for their excellent heat transfer enhancement performance. However, winding and conglobation are constraints against their tribological performance, these constraints can be solved by surfactants. However, the influences of surfactant type and dispersing mechanism on the dispersion effect of CNTs have not been studied systemically. Consequently, this study analyzed the dispersing mechanism of different surfactants and evaluated the dispersion stability and tribological performances of PPO-based CNT nanofluids. Results showed that nanofluids with APE-10 obtain the highest viscosity, lowest friction coefficient, minimum roughness value and favorable surface morphology, thus indicating their excellent dispersion stability and tribological performance. Further, different experimental evaluations confirm that APE-10 is the optimal dispersant of CNT nanofluids.
Sustainable development and green manufacturing are becoming an international consensus in the face of the threat of severe environmental pollution and waste of resources. Cryogenic air (CA) and nanofluid minimum quantity lubrication (NMQL) are state-of-the-art green manufacturing technologies. However, the lubricating performance of cryogenic air is ineffective, and the cooling ability of nanofluids minimum quantity lubrication is unsatisfactory. To specifically address the bottlenecks in these manufacturing methods, a new green processing technology combining their advantages was proposed, namely, cryogenic air nanofluid minimum quantity lubrication (CNMQL). Compared to traditional processing modes and other green technologies, cryogenic air nanofluid minimum quantity lubrication is superior for its economic efficiency, low carbon use, high utilization efficiency, energy saving as well as excellent cooling and lubricating performances. A surface grinding experiment was conducted under three lubricating conditions (cryogenic air, minimum quantity lubrication, and cryogenic air nanofluids minimum quantity lubrication) with Ti–6Al–4V as the workpiece material. Experimental results showed that: cryogenic air nanofluids minimum quantity lubrication achieved the best lubricating effect and obtained minimum specific grinding energy (51.96 J/mm³) and friction coefficient (0.60), followed by nanofluids minimum quantity lubrication and cryogenic air. The lubricating mechanisms under cryogenic air nanofluids minimum quantity lubrication and nanofluids minimum quantity lubrication conditions were also analyzed according to the viscosity of nanofluid lubricants in grinding zone, contact angle, stability of lubricating oil film, atomization effect of droplets, and microtopography of workpiece surface. Relative to other conditions, the higher viscosity and larger contact angle of nanofluid lubricants under cryogenic air nanofluids minimum quantity lubrication condition led to higher stability and better lubricating effect of the lubricating oil film in the grinding zone. Droplets sprayed onto the grinding zone had a larger atomization angle, and the distribution density of droplets in the entire atomization spraying zone was relatively uniform. The droplets were uniformly distributed and had a larger spreading area, facilitating superior atomization effect in the grinding zone. On the other hand, workpiece surface had clear and smooth grinding pipelines, which presented minimal obstruction for the longitudinal flow and horizontal spreading effect of the micrometer pipelines, so the nanofluid lubricants achieved better spreading infiltration effect. Under the joint influence of the above factors, cryogenic air nanofluids minimum quantity lubrication achieved optimal lubricating effect, thus obtaining minimum specific grinding energy and friction coefficient.
Minimum quantity lubrication (MQL) is an efficient, green, and eco-friendly method of applying cutting fluids in machining processes. This study presents the processing characteristics of different vegetable oil-based nanofluid MQL for grinding various workpiece materials. The performance of three lubricant types (i.e., pure palm oil, MoS2 nanofluid, and Al2O3 nanofluid) of good lubrication performance and three types of materials (i.e., Inconel 718, ductile cast iron, and AISI 1045 steel) was evaluated in terms of force ratio, specific grinding energy, and G ratio. The optimal processing combination of lubricants and workpiece materials under the same experimental conditions was obtained using orthogonal experiment. Optimization results were verified by evaluating the morphology of the workpiece surface and grinding debris. Experimental results show the different processing characteristics of materials when various workpieces are processed using dissimilar MQL lubricants. MoS2 nanofluid MQL is suitable for machining soft medium carbon steels, such as 45 steel, while Al2O3 nanofluid is suitable for machining materials of high strength and hardness, such as nickel-based alloys.
This paper discusses the experimental characterization on micro-drilling process of titanium alloy (Ti-6Al-4V), which is one of representative difficult-to-cut materials, with the nanofluid minimum quantity lubrication (nMQL). The miniaturized machine tool system is set up, and then, a series of micro-drilling experiments are performed under compressed air (CA), pure MQL and nMQL for a comparison. For the nanofluid, nanodiamond particles with the sizes of 35 nm and 80 nm are chosen, and the base fluid is vegetable oil. For the micro-drilling process, an uncoated carbide twist drill having the diameter of 300 μm is used for drilling holes in the titanium alloy workpiece. The experimental results show that the nMQL can reduce the drilling torques and thrust forces, but its effect is more obvious at a low feed rate (10 mm/min). In addition, the edge corner radii and hole circularity errors are significantly reduced in the case of small size (35 nm) and high weight concentration (0.4 wt. %) of the nanodiamond particles at the low feed rate. It is also found that the nMQL effectively mitigates chip adhesion of drill tool and burr of drilled holes.
In order to explore the grinding characteristics of cBN-WC-10Co composites, the grinding experiment with a resin bond diamond grinding wheel was carried out. The grinding forces, surface roughness, surface morphology and residual stress were investigated. It was found that the material removal mechanism of cBN-WC-10Co was the combination of the brittle fracture of cBN particles, ductile removal of Co phase, plastic deformation, grain dislodgement and grain crush of WC grains. The brittle removal model resulted in a lower specific grinding energy. The main contributor to the surface roughness was cBN particles. Some cBN particles over the surface of cBN-WC-10Co composites were fractured or pulled out and then formed cavities with different depths, this led to a rougher surface. The surface roughness was increased but the specific grinding energy decreased with an increase of the maximum undeformed chip thickness. A high-level residual compressive stress was induced at WC phase and it was increased with an increase of the depth of cut. The depth of cut has more significant influence on the grinding forces than the table speed or the wheel speed.
A study of microscale skull bone grinding temperature field under different cooling conditions is presented and discussed. Micro-grinding model, heat flux density model, convective heat transfer coefficient model and intra-workpiece heat conduction model are developed, based on which, a simulation study on microscale bone grinding temperature field under dry grinding, drip cooling, mist cooling, and nanoparticle jet mist cooling (NJMC) is performed. Simulation results show that NJMC displayed the lowest temperature peak (27.5 °C), followed by mist cooling, drip cooling, and dry grinding successively. A verification experiment using fresh bovine femur bone is performed under different cooling conditions. Results find that the temperature peak of dry grinding is 41.6 °C, which is 10.1%, 29.3%, and 37% higher than those of drip cooling, mist cooling, and NJMC, respectively, verifying the optimal cooling effect of NJMC. The experimental results are consistent with the theoretical analysis results, confirming the validity of the theoretical models.
This study investigates the critical maximum undeformed equivalent chip thickness for ductile-brittle transition (DBhmax-e) of zirconia ceramics under different lubrication conditions. A DBhmax-e model is developed through geometry and kinematics analyses of ductile-mode grinding. Result shows that DBhmax-e decreases with increasing friction coefficient (μ). An experimental investigation is then conducted to validate the model and determine the effect of dry lubrication, minimum quantity lubrication (MQL), and nanoparticle jet minimum quantity lubrication (NJMQL) conditions on DBhmax-e. According to different formation mechanisms of debris, the grinding behavior of zirconia ceramics is categorized into elastic sliding friction, plastic removal, powder removal, and brittle removal. Grinding forces per unit undeformed chip thickness (Fn/h and Ft/h) are obtained. The lubrication condition affects the normal force and ultimately influences the resultant force on workpiece. In comparison with dry grinding (DBhmax-e = 0.8 μm), MQL and NJMQL grinding processes increase DBhmax-e by 0.99 and 1.79 μm respectively; this finding is similar to model result. The theoretical model is then assessed by different volume fractions of nanofluids under NJMQL condition with an average percentage error of less than 8.6%.
Numerous researchers have developed theoretical and experimental approaches to force prediction in surface grinding under dry conditions. Nevertheless, the combined effect of material removal and plastic stacking on grinding force model has not been investigated. In addition, predominant lubricating conditions, such as flood, minimum quantity lubrication, and nanofluid minimum quantity lubrication, have not been considered in existing force models. This work presents an improved theoretical force model that considers material-removal and plastic-stacking mechanisms. Grain states, including cutting and ploughing, are determined by cutting efficiency (β). The influence of lubricating conditions is also considered in the proposed force model. Simulation is performed to obtain the cutting depth (ag) of each “dynamic active grain.” Parameter β is introduced to represent the plastic-stacking rate and determine the force algorithms of each grain. The aggregate force is derived through the synthesis of each single-grain force. Finally, pilot experiments are conducted to test the theoretical model. Findings show that the model's predictions are consistent with the experimental results, with average errors of 4.19% and 4.31% for the normal and tangential force components, respectively.
An investigation into the effect of nanofluid minimum quantity lubrication (MQL) on the temperatures in surface grinding is presented and discussed. Six types of nanoparticles, namely molybdenum disulfide (MoS2), zirconium dioxide (ZrO2), carbon nanotube (CNT), polycrystalline diamond, aluminum oxide (Al2O3), and silica dioxide (SiO2), are considered to mix individually with a pollution-free palm oil in preparing the nanofluids. A commonly used Ni-based alloy is chosen as the workpiece material. It is shown that CNT nanofluid results in the lowest grinding temperature of 110.7 °C and the associated energy proportionality coefficient of 40.1%. Furthermore, the relevant physical properties of the nanofluids such as the coefficient of thermal conductivity, viscosity, surface tension and the contact state between the droplets and workpiece surface (contact angle) are discussed to shine a light on their effect on the cooling performance. A mathematical model for convective heat transfer coefficient is then developed based on the boundary layer theories. The model calculation indicates that the CNT nanofluid has the highest heat transfer coefficient (1.3 × 10⁴ W/(m K)) which to some extent explains why CNT nanofluid MQL gives the lowest grinding temperature.
Lubricants play a critical role in machining, especially in the grinding process. As a result of the growing need for environmental protection and the increasing number of health problems faced by workers, traditional lubricants are gradually being replaced. Nanofluids, which contain nanoparticles in the proper base fluid, can serve as a low-carbon, “green” lubricant. As a lubricant, nanofluids show improved heat transfer capability and lubricating properties. Friction between abrasive grains and workpieces during grinding can directly influence grinding force, grinding wheel wear, and workpiece quality. Therefore, increasing lubricating effects is an effective way to improve machining performance. In this study, a nanofluid, as the lubricating fluid, is developed by adding 0.5 vol% to 4.0 vol% Al2O3 nanoparticles to palm oil for the surface grinding of a Ni-based alloy in minimum quantity lubrication (MQL) mode. The tribological performance at the grinding wheel/workpiece interface under different concentrations of nanoparticles is studied on the basis of macroparameters (force ratio, specific energy, and G-ratio) and microparameters (surface quality, microstructure of abrasive grains and grinding debris, viscosity, and contact angle). Results show that the nanofluid flows through the grinding wheel and workpiece interface and forms a lubricating oil film that reduces friction significantly. An optimum concentration of nanoparticles is also achieved. The smallest force ratio of 0.281 is obtained when the volume concentration of the nanoparticles is 1.5%, whereas the minimum roughness of Ra = 0.301 μm, slender grinding debris, and maximum drop wetting area are realized when the volume concentration is 2.0%. Hence, the nanofluid exhibits excellent overall tribological performance. In addition, a nonlinear relationship exists between the lubricating effect and the concentration of the nanofluid. The appropriate concentration of Al2O3 in the nanofluid thus provides good tribological performance and have both environmental and economic benefits for industrial applications.
Vegetable oil is employed as base fluid in precision grinding because of its biodegradability and non-pollutant properties. Castor oil exhibits superior lubrication performance to other vegetable oils, but its high viscosity and poor flow limit its application in industrial production. In this study, castor oil was used as base oil and individually mixed with six other kinds of vegetable oils (i.e., soybean, maize, peanut, sunflower, palm, and rapeseed oils) at a ratio of 1:1 to change the rheological properties of the former. Each mixture was obtained as base oil for minimum quantity lubrication grinding. The high-temperature nickel-based alloy GH4169 was used as workpiece to evaluate the lubrication performance at the grinding wheel/workpiece interface. The mechanism of lubrication was also studied based on the molecular structure of vegetable oil. Specific grinding force, specific grinding energy, surface roughness, surface microtopography, and grinding debris were compared among the experimental and comparison groups (castor oil). The workpiece surface profile was analyzed using the correlation function and cross-correlation coefficient. Results indicated that the comprehensive lubricating performance of mixed oil was superior to that of castor oil, and soybean/castor oil exhibited the optimal performance. The specific tangential grinding force and specific normal grinding force were 0.664 and 1.886 N/mm, respectively, with 27.03% and 23.15% reduction, respectively, with respect to those of castor oil. The surface profile curves of the workpiece obtained from four kinds of working conditions (castor oil, castor/soybean oil, castor/maize oil, and castor/palm oil) were also analyzed. The amplitude of the surface profile curve in castor/soybean oil is larger and the correlation coefficient is higher (0.51) than those under other mixed oils; hence, the workpiece showed the optimal surface quality.
Engine oil is a type of lubricants and coolants that is used in internal combustion engines. In this paper, an examination of viscosity of MWCNTs/ZnO-SAE40 hybrid nano-lubricants under various temperatures and solid volume fractions is presented. The experiments performed at temperature ranging from 25 °C to 60 °C and solid volume fractions of 0, 0.05%, 0.075%, 0.1%, 0.2%, 0.4%, 0.5%, 0.75% and 1%. The results revealed that the nano-lubricant behaves as Newtonian fluid. Viscosity measurements also showed that the viscosity decreases with increasing temperature and increases with an enhancement in the solid volume fraction. Using experimental data, relative viscosity indicated that the maximum enhancement of viscosity of the nano-lubricant was 33.3%. This occurred at solid volume fraction of 1.0% and temperature of 40 °C. Based on experimental results, the correlation has been proposed to estimate the viscosity of MWCNTs/ZnO-SAE40 hybrid nano-lubricants.
The current study investigates the influence of applying cryogenic liquid nitrogen cooling and minimum quantity lubrication (MQL) in drilling glass aluminium reinforced epoxy (GLARE) fibre-metal laminates. Cutting forces, surface roughness, cutting tool condition and post-machining microhardness of the surface of the upper and lower aluminium sheets near the edge of drilled holes were investigated. The findings are also compared with results from previous dry drilling trials of a similar GLARE grade. An analysis of variance ANOVA was carried out to evaluate the impact of cutting parameters, and cooling conditions, and their percentage contributions when drilling GLARE. The use of MQL and cryogenic liquid nitrogen coolants increased the cutting forces; however, they both reduced the surface roughness of machined holes, adhesions and built-up edge formation on the cutting tool compared to dry drilling. Inspection of post-machining microhardness of the upper and lower aluminium sheets near the hole edges showed that it increased when using both coolants.
A three-dimensional thermal model that the grinding wheels are simplified as a moving heat source in the rail grinding process was established and used to explore the effect of grinding parameters on the temperature field of ground rail. The results indicate that the highest temperature of ground rail increases with an increase in the grinding power. The increase of grinding surface width and moving velocity causes a fall of ground rail temperature. It should be noted that the temperature of ground rail would continue to rise when the first car with 12 grinding wheels passes through the rail surface. However, the temperature does not increase when the second car passes through. Compared with distributing on the same grinding surfaces, two grinding wheels distributing on two adjacent grinding surfaces would lower grinding rail temperature. The results are beneficial to improve the reasonable arrangement of grinding wheels in the rail grinding process.
Different nanoparticles exhibit various physicochemical properties (e.g., structure and shape), which can influence their lubricating properties. In this work, six nanofluids, namely, MoS2, SiO2, diamond, carbon nanotubes (CNTs), Al2O3, and ZrO2, were used as minimum quantity lubrication grinding fluids to select the kind of nanoparticles with optimum lubrication performance in grinding nickel alloy GH4169. Experimental results concluded the following: 1) Nanoparticles with spherical or sphere-like molecular structure and nanofluids with high-viscosity demonstrate superior lubrication performances. 2) The polishing effect of nanodiamond particles enhances their surface morphology. 3) The lubricating property of the six nanofluids is described in the following order: ZrO2<CNTs<ND<MoS2<SiO2<Al2O3.
Abstract In any metal cutting operation, the cutting fluid plays a vital role by cooling the surface of the work piece and the cutting tool, removing chips from the cutting zone and by lubricating the tool-work piece interface. However, misuse of the cutting fluid and wrong methods of its disposal can affect human health and the environment badly. Also, it accounts for 16 - 20% of the total cost of manufacturing in the production industry. Among various techniques available on application of the coolant, researchers, of late, have been focussing on Near Dry Machining (NDM)/Minimum Quantity Lubrication (MQL) as it minimizes the use of coolant by spraying the mixture of compressed air and cutting fluid in an optimized manner instead of flood cooling. The MQL technique has proved to be suitable because it complies with the requirements of ‘green’ machining. This paper presents a review of the important research papers published regarding the MQL-based application of mineral oils, vegetable oils and nanofluid-based cutting fluids for different machining processes, such as, drilling, turning, milling and grinding, etc. The paper explains the mechanism of the MQL technique. In a systematic manner, the present work also discusses its effect on the performance parameters of different machining processes. Most of the experimental studies have shown that application of MQL produces surface better than dry machining and similar to that as produced under wet machining. Its application also reduces cutting forces, cutting zone temperature, tool wear, friction coefficient in comparison to dry and wet machining. Therefore, MQL technique has proved to be a viable alternative to the flood lubrication under similar performance parameters.
Given the increasing attention to environmental and health problems caused by machining, the development of an environment-friendly grinding fluid has become an urgent task. As an environment-friendly grinding fluid, vegetable oil has gained considerable attention. In this study, seven typical vegetable oils (i.e., soybean, peanut, maize, rapeseed, palm, castor, and sunflower oil) were used as the minimum quantity lubrication (MQL) base oil to conduct an experimental evaluation of the friction properties of the grinding wheel/workpiece interface. With nickel-based alloy GH4169 as workpiece material, the flood grinding working condition and MQL grinding working condition (i.e., using the seven vegetable oils and paraffin oil) were selected. The evaluation of the lubrication property mainly referred to grinding force, friction coefficient, specific grinding energy, and grinding ratio (G-ratio), as well as surface morphology and surface roughness. Experimental results indicated that MQL grinding using vegetable oil achieved a lower friction coefficient, specific grinding energy, and grinding wheel wear than flood grinding. Among the grinding fluids, castor oil achieved the best lubrication property and the best surface quality of workpiece. Castor oil had a friction coefficient and specific grinding energy of 0.30 and 73.47 J/mm3, which decreased by 50.1% and 49.4%, respectively, compared with flood grinding. Moreover, various grinding fluids changed cutting forces through changes in their lubrication property and further changed G-ratio. However, lubrication property was one of factors that influenced the G-ratio. Maize oil had the highest G-ratio of 29.15. Peanut, sunflower, and soybean oil with more saturated fatty acids, castor oil with more castor acids, and palm oil with numerous palmitic acids were suitable as lubricating fluids.
This study presents an experimental study of the effect of solid volume fraction and Reynolds number on heat transfer coefficient and pressure drop of CuO-Water nanofluid. Pure Water and nanofluid with particle volume fractions of 0.0625%, 0.125%, 0.25%, 0.5%, 1%, 1.5% and 2% are used as working fluids. Nanofluids were flowed inside a horizontal double-tube counter flow heat exchanger under turbulent flow regime. Flow Reynolds numbers of each volume fraction of nanofluid were between from 2900 to 18500 during the experiments. The Result shows that generally heat transfer coefficient of nanofluids is higher than that of base fluid. Moreover, it is observed that heat transfer coefficient and Nusselt number of nonofluids increases with an increase in solid volume fraction and Reynolds number. But the rate of this increase in low Reynolds numbers was more than that at high Reynolds numbers. The measurements also show that the pressure drop of nanofluid is slightly higher than that of the base fluid and increases with an increase in the nanoparticles volume fraction. But the rate of this increase in low Reynolds numbers was more than that at high Reynolds numbers. Therefore, it can be concluded that the effect of increasing percentage of nanoparticle in low Reynolds number of this research is stronger than that of high Reynolds number. Moreover, friction factors were calculated and compared with blasious correlation. Finally, in order to find the optimum condition of this nanofluid for practical applications, thermal performance factor was defined to consider increasing Nusselt ratio besides increasing friction ratio simultaneously. The results show that the maximum thermal performance factor of this nanofluid was 1.266, which was calculated for 2% nanoparticle volume fraction at Reynolds number 3677.
Laser cutting of a cBN-WC-10Co composite material was carried out using a pulsed Nd: YAG laser. The cutting characteristics, as well as the changes in microstructure and mechanical property, were investigated. It was found that cracks were induced by laser machining on the sub-surface and the evidence of phase transformation from cBN to hBN was observed on the cut surface. Cutting parameters had significant effect on the cut surface. A higher laser power produced a smoother cut surface, but a larger heat-affected zone, in comparison to the lower laser power used. No radical cracks were found on the cross-section at the laser power of 100 W. The surface roughness and the heat-affected zone depth decreased with the increased cutting speed and the gas pressure. The material removal involved in the laser cutting of cBN-WC-Co composite was attributed to the melting or evaporation of cBN and WC-Co. The dropping of cBN particles from the cut surface was also found during the cutting at the laser power of 30 W for the loss of the supporting from the WC-Co matrix.
This paper presents an overview of the recent advances in high performance cutting of aerospace alloys and composite currently used in aeroengine and aerostructure applications. Progress in cutting tool development and its effect on tool wear and surface integrity characteristics of difficult to machine materials such as nickel based alloys, titanium and composites is presented. Further, advances in cutting technologies are discussed, focusing on the role of hybrid machining processes and cooling strategies (MQL, high pressure coolant, cryogenic) on machining performance. Finally, industrial perspectives are provided in the context of machining specific components where future challenges are discussed.
A heat transfer model for grinding has been developed based on the finite difference method (FDM). The proposed model can solve transient heat transfer problems in grinding, and has the flexibility to deal with different boundary conditions. The model is first validated by comparing it with the traditional heat transfer model for grinding which assumes the semiinfinite workpiece size and adiabatic boundary conditions. Then it was used to investigate the effects of workpiece size, feed rate, and cooling boundary conditions. Simulation results show that when the workpiece is short or the feed rate is low, transient heat transfer becomes more dominant during grinding. Results also show that cooling in the grinding contact zone has much more significant impact on the reduction of workpiece temperature than that in the leading edge or trailing edge. The model is further applied to investigate the convection heat transfer at the workpiece surface in wet and minimum quantity lubrication (MQL) grinding. Based on the assumption of linearly varying convection heat transfer coefficient in the grinding contact zone, FDM model is able to calculate convection coefficient from the experimentally measured grinding temperature profile. The average convection heat transfer coefficient in the grinding contact zone was estimated as 4.2 x 10(5) W/m(2)-K for wet grinding and 2.5 x 10(4) W/m(2)-K for MQL grinding using vitrified bond CBN wheels. [DOI: 10.1115/1.4003947]
Nano-scale Al2O3 spherical particles, prepared via a hydrothermal method and modified by silane coupling agent, can be well-dispersed in lubricating oil. The tribology properties of Al2O3 nanoparticles as lubricating oil additives have been studied by four-ball and thrust-ring friction test, which illustrate that the modified Al2O3 nanoparticles can effectively improve the lubricating behaviors compared to the base oil. When the added concentration is 0.1 wt%, the friction coefficient and the wear scar diameter are both smallest. The lubrication mechanism is that a self-laminating protective film is formed on the friction surface and the wear behavior changes from sliding friction to rolling friction.
Tribological investigations were performed on mineral oil containing Fe, Cu and Co nanoparticles and their combinations. The tribological tests showed that each set of nanoparticles significantly reduced the friction coefficient and wear (up to 1.5 times) of friction pairs. The use of Cu nanoparticles provides the most effective reduction of friction and wear in each combination of nanoparticles. Surface analysis shows that the constituent elements of nanoparticles precipitated on the contact surface during the use of the oils with nano-additives. Different structures formed on the friction surface are observed in the contact zone and over the remainder of the ball surface. The SEM micrographs and EDX chemical analysis confirm the formation of a tribo-layer composed of the elements from the nanoparticles.
A brass vortex tube with changeable parts is used to obtain the optimum nozzle intake numbers and diameter. The effects of inlet pressure and CF (cold fraction) are also investigated. Results illustrate that increasing the number of nozzles causes a temperature drop and the optimum nozzle diameter corresponds to quarter of vortex tube diameter. The distance between cold end orifice and nozzle intakes is investigated in this work and it is found that for a better performance, this distance should be decreased. A series of experiments conducted to investigate the CF effect on VT performance and an optimum amount for this parameter is found. A two-dimensional computational fluid dynamics simulation of a VT has been carried out as well. CFD code is applied to investigate the role of nozzle diameter on the temperature separation. The highly rotating flow field structure and its characteristic are simulated and analyzed with respect to various operating inlet pressure ranges and different CFs. Finally, some results of the CFD models are validated by the available experimental data, showing reasonable agreement for future development.
Nanofluid, fluid suspensions of nanometer sized particles are revolutionizing the field of heat transfer area. Addition of nano particles to the base fluid also alters the lubricating properties by reducing the friction. In grinding process, friction between the abrasive grains and the workpiece is a key issue governing the main grinding output. It has a direct influence on grinding force, power, specific energy and wheel wear. Moreover, high friction force increases the heat generation and lead to thermal damage in the surface layer of the ground work. Hence, any effort towards the friction control will enhance the component quality significantly. In this study, nanofluid as metalworking fluid (MWF) is made by adding 0.05, 0.1, 0.5 and 1% volume concentration of Al2O3 and CuO nano particles to the water during the surface grinding of Ti-6Al-4V in minimum quantity lubrication (MQL) mode. Surface integrity of ground surface, morphology of the wheel, and chip formation characteristics are studied using surface profilometer, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and stereo zoom microscopy (SZM). Coefficient of friction was estimated On-Machine using the measured forces. The results showed that the type of nano particle and its concentration in base fluid and the MQL flow rate play a significant role in reducing friction. Application of nanofluid leads to the reduction of tangential forces and grinding zone temperature. The cooling effect is also evident from the short C-type chip formation. MQL application with Al2O3 nanofluid helps in effective flushing of chip material from the grinding zone, thereby solving the main problem during the grinding of Ti-6Al-4V.