Article

On The Measurement of Temperature in Material Removal Processes

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Abstract

Because it is key to understanding the performance of material removal processes and resultant workpiece quality, the measurement of temperature during material removal is done extensively. We review several widely used temperature measurement methods and show how they can be applied to temperature monitoring during material removal. Since there is little documentation on measurement uncertainties as relates to material removal, this paper outlines the physics of each method, detailing the sources and evaluation of uncertainty. Finally, using criteria critical in measuring material removal, methods are compared, and the results presented in guide-format for participants in this field of work.

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... For more than 100 years, cutting temperature has been the most examined cutting characteristic [12]. During this time, numerous important developments have taken place in analytical models for the calculation of temperature [13] as well as in experimental investigations [14,15] into the temperature distribution in tools, workpieces and in the contact between these objects [16][17][18]. In the first phase, the heat distribution in the layout of the heat exchange for cutting processes was assumed to be a plane process [19]. ...
... When calculating the temperature distribution in the length of the plastic contact, it was assumed that the temperature can be calculated according to the maximum heat flow density and temperature (Eqs. (17) and (20)) in a point of the rake face at a distance C H (Fig. 1) from the cutting edge. To simplify the subsequent calculations, the length of the considered area C H was assumed to be 1 due to the transition to the dimensionless coordinate ...
... The distribution of heat flow density and temperature was represented as a joint effect of the evenly distributed heat sources with the density of the heat flow q 0 (Eq. (17)) and the evenly distributed heat dissipations. These heat dissipations were introduced individually into each interval. ...
Article
A methodology for temperatures calculating in different cutting zones is proposed, taking the peculiarities of heat distribution for moving sources into account. For this, the correlation was established between the heat flow densities and temperatures in the chip forming area, in the stagnation zone as well as in the zone of plastic contact between the chip and the tool. The method for temperature calculation was based on the joint solution of the heat conduction equation and the constitutive equation of the machined material. A significant simplification of the temperature calculation was achieved without sacrificing accuracy by considering the features of the heat propagation from fast-moving sources. Taking into account material softening, the temperature and heat flow density distributions along the tool rake and clearance faces and in the stagnation zone were numerically calculated. The developed models were confirmed by experiment. The comparison showed good agreement between theoretical and experimental results.
... This makes it challenging to fix the thermocouples on the rotating spindles. 2 Polymethyl methacrylate (PMMA) has been recently adopted in the medical field due to its biocompatibility, vertebrae in osteoporotic people. 3 The materials' high scratch and impact resistance properties have also attracted its application in the manufacturing of microsensors used in medical devices and other drug delivery devices. ...
... Regression analyses were conducted for the two temperature sets (dependent variables) to establish their relationship with the parameters (independent variables). 24 Two linear regression models for the maximum and average milling temperatures were developed, as shown in equations (2) and (3): ...
... T max ( • C) = 54.9 + 0.01144S + 18.37D − 0.0641F (2) T Avg ( • C) = 54.8 + 0.011465S + 15.39D − 0.0655F (3) The two linear models yielded R 2 values of 0.7566 and 0.7383, respectively. Further, plots of the experimental maximum and average temperatures against the predicted values were produced as shown in Supplemental Figure 9(a) and (b), respectively. ...
Article
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Conventional machining of materials is often characterized by the generation of heat and elevation of cutting point temperatures. This induces thermal transformations and development of residual stresses. Therefore, there is a necessity to evaluate the interaction of machining temperatures with heat generation to identify the optimal values for the least heat generation. This is the main aim of this study, where an analysis of temperature is conducted during the computer numerical control (CNC) milling of medical-grade poly(methyl methacrylate) (PMMA). The samples were obtained from used optical lenses with an average Shore D hardness and transparency of 79.1 and 89.2%, respectively. The experiments were designed using the Taguchi methodology. The milling parameters used were the spindle speed, depth of cut, and feed rate. A special adjustable jig and several fixtures were developed for workpiece holding. During the milling process, in-situ temperature monitoring was undertaken using a FLIR-E63900 Infrared Thermometer. From the analysis, the parameter combination for the least values of maximum and average temperatures was a spindle speed of 1250 rev/min, a depth of cut of 0.3 mm, and a feed rate of 350 mm/min. A one-way analysis of variance depicted that the spindle speed was the most significant parameter toward the maximum and average milling temperatures owing to the generated friction and cutting forces. The depth of cut and feed rate were insignificant to the temperature of the process. It is also reported that the spindle speed exhibited a direct relationship produced by the machining forces whereas the feed rate exhibited an inverse relationship with the machining temperature, which was attributed to the reduced contact time and high chip removal, hence high heat dissipation. Lastly, a regression analysis was conducted, which showed that the maximum ( R ² = 0.7566) and average temperatures ( R ² = 0.7383) during the CNC milling of medical-grade PMMA could be predicted using linear regression models.
... Their work also provides an insight into the background theory for each methodology. Davies et al. [15] reviewed the methodologies applicable for material removal processes, giving a historical overview of the advancements in temperature measurement for material removal processes. The authors provided a brief overview on the background theory for each methodology and proceeded to discuss major work performed in various material removal processes, highlighting the capabilities and challenges faced in each process. ...
... The use of thermocouple sensors is the most common conductive temperature measurement technique [57,58]. The principal factors for thermocouple use is that they are durable, can be relatively inexpensive, and are able to operate over a wide range of temperatures [14,15]. There are several ways to implement thermocouples to obtain temperature measurements during machining, as shown in Figure 2. ...
... Non-contact, or radiative, measurement techniques interpret and measure the thermal energy, in the form of infrared (IR) radiation, emitted by an object of interest to determine its thermodynamic temperature based on the wavelength of the emitted radiation [15,88]. This often allows for non-intrusive temperature measurements to be taken from a distance [56]. ...
Article
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During the machining process, substantial thermal loads are generated due to tribological factors and plastic deformation. The increase in temperature during the cutting process can lead to accelerated tool wear, reducing the tool’s lifespan; the degradation of machining accuracy in the form of dimensional inaccuracies; and thermally induced defects affecting the metallurgical properties of the machined component. These effects can lead to a significant increase in operational costs and waste which deviate from the sustainability goals of Industry 4.0. Temperature is an important machining response; however, it is one of the most difficult factors to monitor, especially in high-speed machining applications such as drilling and milling, because of the high rotational speeds of the cutting tool and the aggressive machining environments. In this article, thermocouple and infrared radiation temperature measurement methods used by researchers to monitor temperature during turning, drilling and milling operations are reviewed. The major merits and limitations of each temperature measurement methodology are discussed and evaluated. Thermocouples offer a relatively inexpensive solution; however, they are prone to calibration drifts and their response times are insufficient to capture rapid temperature changes in high-speed operations. Fibre optic infrared thermometers have very fast response times; however, they can be relatively expensive and require a more robust implementation. It was found that no one temperature measurement methodology is ideal for all machining operations. The most suitable temperature measurement method can be selected by individual researchers based upon their experimental requirements using critical criteria, which include the expected temperature range, the sensor sensitivity to noise, responsiveness and cost.
... Their work also provides an insight into the background theory for each methodology. Davies et al. [15] reviewed the methodologies applicable for material removal processes, giving a historical overview of the advancements in temperature measurement for material removal processes. The authors provided a brief overview on the background theory for each methodology and proceeded to discuss major work performed in various material removal processes, highlighting the capabilities and challenges faced in each process. ...
... The use of thermocouple sensors is the most common conductive temperature measurement technique [57,58]. The principal factors for thermocouple use is that they are durable, can be relatively inexpensive, and are able to operate over a wide range of temperatures [14,15]. There are several ways to implement thermocouples to obtain temperature measurements during machining, as shown in Figure 2. ...
... Non-contact, or radiative, measurement techniques interpret and measure the thermal energy, in the form of infrared (IR) radiation, emitted by an object of interest to determine its thermodynamic temperature based on the wavelength of the emitted radiation [15,88]. This often allows for non-intrusive temperature measurements to be taken from a distance [56]. ...
... Historical background of cutting temperature measuring methods in metal cutting. [62] Reproduced with permission from Ref. [62]. Copyright Elsevier (2007). . ...
... Historical background of cutting temperature measuring methods in metal cutting. [62] Reproduced with permission from Ref. [62]. Copyright Elsevier (2007). . ...
Article
The demand for high temperature-resistant superalloys such as Inconel 718 is increasing rapidly, as they possess superior mechanical, chemical, and physical properties. Hence, these materials are highly adaptable for aerospace, nuclear, and marine applications. Nonetheless, during machining of such alloys, high temperatures develop at the interface region. It accelerates the tool wear and adversely affects the integrity of the prepared surfaces. Although conventional metalworking fluids are competent in normalizing/limiting the cutting-edge temperature, the environmental obligations and health issues to the workers have forced the manufacturing industry to move towards environment-friendly machining process, viz. dry machining. High-speed machining of Inconel 718 (under dry condition) can lead to the attainment of high cutting temperatures, thereby activating the mechanisms of built-up-edge (BUE) development and diffusion, leading to enhanced wear rate of tool. Besides, high temperatures can alter the integrity, infuse residual stresses, and promote crack generation/propagation on the processed surface. Therefore, the present paper contributes a detailed insight into heat generation during machining of Inconel 718 and its influence on various machining responses. Additionally, the work addresses multiple possibilities to reduce the cutting temperature with due emphasis on distinct machining methodologies, viz. dry, wet, and tool texturing. Abbreviations: BUE: Built-up Edge; AISI: American Iron and Steel Institute; AJM: Abrasive Jet Machining; AlTiN: Aluminium Titanium Nitride; Al2O3: Aluminum Oxide or Alumina; Al2O3/SiC: SiC whisker-reinforced alumina Al2O3 ceramic; Al2O3-TiC: TiC added alumina ceramic; AS: Conventional tool; AT-PA: Parallel grooves; AT-PE: Perpendicular grooves; AT-W: Wavy pattern; CaF2: Calcium fluoride; CBN: Cubic boron nitride; CBN-OR: Perpendicular to cutting edge; CBN-ORE : Perpendicular grooves 30 µm away from main cutting edge; CBN-PA: Parallel to cutting edge; CFT: Nano textured tool; CFT WS: Nano textured with soft coated WS2; CrN: Chromium Nitride; CT: Conventional cutting tool; DOC notch wear: Depth-of-cut notch wear; EBSD: Electron back scatter diffraction; ECM: Electrochemical machining; FCC: Face centered cubic; GWP: Global warming potential; HPC: High-pressure cooling; HPJ: High-pressure jet; HPJA: High-pressure jet assistance; HRSA: Heat-resisted super alloy; HSS: High-speed steel; IPF: Inverse pole figure; ISO: International organization for standardization; l/h: liter/hour; L/min: Liter/minute; Micro-EDM: Micro-electrical machining; MoS2: Molybdenum disulfide; MQL: Minimum quantity lubrication; MWFs: Metal-working fluids; NIOSH: National Institute of Occupational Safety and Health; PCBN: Polycrystalline Cubic Boron Nitride; PVD: Physical vapor deposition; SEM: Scanning electron microscope; Si3N4: Silicon nitride; ST: Graphite soft-coated tool; STT-F: Linear grooves on the flank surface; STT-R: Elliptical textures on the rake face; STT-0: Plain WC/Co carbide tool; STT-1: Elliptical grooves; STT-2: Parallel grooves; STT-3: Perpendicular grooves; TiAlN: Titanium Aluminium Nitride; TiCN: Titanium Carbonitride; TiN: Titanium Nitride; T-IPA: Perpendicular textures to chip flow; T-IPE: Parallel textures to the chip flow; T-PA: Texture surfaces inclined an angle to the chip flow; TT: Textured tool under dry condition; TT+SL: Textured tool under solid lubricant-assisted MQL cooling conditions; T1: Un-textured tool; T2: Texture tool having circular pit holes; T3: Hybrid texture tool combination of circular pit holes and linear grooves; TT: Textured inserts; TT: WS2-soft-coated WS2 textured tool; T1: Conventional insert; T2: Conical dimple-textured tool; T3: Square dimple-shaped insert; T4: Scratches provided on the cutting insert; T-1: Untextured insert; T-2: Pit holes textured insert; T-3: Hybrid textured insert; US: United States; USM: Ultrasonic Machining; WC: Tungsten carbide; WC–Co: Tungsten carbide-cobalt; WEDM: Wire electrical discharge machining; WS2: Tungsten disulfide
... Although the main reason for continued temperature measurement work is to improve the quality of the finished part, and it can also help predict tool wear and the development of predictive modeling software. In addition, studies have shown that, in material removal processes, a phenomenon that can degrade the quality of the piece, they often follow an Arrhenius model (exponential type), implying that some otherwise incompatible behaviors can actually be attributed to variations of temperature [7]. ...
... For cutting temperature measurement, a digital infrared thermometer was used, and a measurement technique already established in the literature [7,8,47] coupled to a computer running data acquisition software was applied. e thermometer was always directed to the cutting area, as shown in Figure 3(b), in a distance of about 800 mm thereof. ...
Article
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This study aims to correlate the influence of thermal and microstructural parameters such as growth rate and cooling rate (VL and TR) and secondary dendrite spacing (λ2), respectively, in the machining cutting temperature and tool wear on the necking process of the Al–7 wt.% Si alloy solidified in a horizontal directional device using a high-speed steel with a tungsten tool. The dependence of λ2 on VL and TR and dependence of the maximum cutting temperature and maximum flank wear on λ2 were determined by power experimental laws given by λ2 = constant (VL and TR)ⁿ and TMAX, VBMAX = constant (λ2)ⁿ, respectively. The maximum cutting temperature increased with increasing of λ2. The opposite occurred with the maximum flank wear. The role of Si alloying element on the aforementioned results has also been analyzed. A morphological change of Si along the solidified ingot length has been observed, that is, the morphology of Si in the eutectic matrix has indicated a transition from particles to fibers along the casting together with an increase of the particle diameters with the position from the metal/mold interface.
... During this period, well-established methods and procedures for determining thermal properties have been developed. The basic procedures for determining these properties specifically for material removal processes are outlined in a review by Davies and colleagues [27]. Most publications on the modeling of cutting processes have taken the thermal properties of the machined material from the constant values included as standard in the simulation software (see e.g., [28][29][30][31][32]). ...
... The temperature distribution within the primary zone, inside the area bounded by the indicated temperature isolines (see Fig. 1), is approximately constant compared with the temperature distribution in the secondary and tertiary cutting zones, in which there is a temperature gradient of up to 5 °C/μm [27,53,54,57]. Moreover, the accessibility to the temperature measurement of the primary cutting zone is considerably better and more comfortable than in other cutting zones, because the temperature can be measured at the exterior surface of the chip during the transition from workpiece material to chip (see Fig. 1). ...
Article
Full-text available
Thermal properties of machined materials, which depend significantly on the change in cutting temperature, have a considerable effect on thermal machining characteristics. Therefore, the thermal properties used for the numerical simulation of the cutting process should be determined depending on the cutting temperature. To determine the thermal properties of the machined materials, a methodology and a software-implemented algorithm were developed for their calculation. This methodology is based on analytical models for the determination of tangential stress in the primary cutting zone. Based on this stress and experimentally or analytically determined cutting temperatures, thermal properties of the machined material were calculated, namely the coefficient of the heat capacity as well as the coefficient of thermal conductivity. Three variants were provided for determining the tangential stress: based on the yield stress calculated using the Johnson-Cook constitutive equation, based on the experimentally determined cutting and thrust forces as well as by directly calculating the tangential stress. The thermal properties were determined using the example of three different materials: AISI 1045 and AISI 4140 steel as well as Ti10V2Fe3Al titanium alloy (Ti-1023). With the developed FE cutting model, the deviation between experimental and simulated temperature values ranged from approx. 7.5 to 14.4%.
... In addition, changes in the microstructure of heated tool materials, such as cemented tungsten carbide, are insignifi cant. Thermosensitive coating methods (PVD fi lms [10] and thermal paints [13]) have high inertness and low accuracy in measuring temperature fi elds due to differences in the thermophysical characteristics of the coating material and the study object material, and the processes of heat transfer between them. ...
... Because of the change in the vector rotation direction, after passing through the wave plate, the resulting beam becomes vertically polarized and is refl ected from the diagonal beam splitter surface toward the lens (11) of the camera (12). A collimated backlight was used (13) to determine the tool and workpiece contours. A strain gauge multicomponent dynamometer (14) with an amplifi er (15) and an analog-to-digital converter (16) were used to record the force components during the cutting process. ...
Article
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Introduction. The efficiency of the metalworking processes highly depends on the performance of the implemented cutting tools that can be increased by studying its stress-strain state and temperature fields. Existing stress analysis methods either have a low accuracy or are inapplicable for research during the operation of the tools made of materials with high mechanical properties. In addition, the study of temperature fields using known methods is difficult due to the small size of the cutting zone, high temperatures, and a heavy temperature gradient appearing during metal cutting. The purpose of this study is to develop new experimental methods for measuring the stress-strain and temperature fields in the cutting tool during its operation using laser interferometry. The methods include: obtaining interference fringe patterns using an interferometer with the original design, obtaining the tool deformation field during the cutting process by recording the changes in interference fringe patterns using a high-speed camera, processing fringe patterns with the separation of deformations caused by heating and cutting forces, and calculating temperature fields and stress distributions using mechanical properties and the coefficient of thermal expansion of the tool material. The advantages of the developed methods include: applicability under real operating conditions of the cutting tool, ability to study the non-stationary stress-strain state and temperatures during an operation, and achievement of a high spatial resolution and a small field of view for the investigated surface. Results and Discussion. The experimental study confirmed the efficiency of the methods. The results of the study included the fields of stresses and temperatures obtained during the orthogonal cutting of heat-resistant steel with a tool made of cemented tungsten carbide WC-8Co. The developed methods can be used to study the cutting tool efficiency at close to real conditions and in obtaining boundary conditions for the study stress-strain state of a workpiece material near the cutting zone.
... The focus of several publications has been on determining the thermal properties of different materials. The general procedure for establishing these properties is described in [13], for example. The thermal properties of materials have mainly been determined by experiment (see e.g. ...
... This occurs already in the stagnant area of the secondary cutting zone [38], [41]. The temperature distribution within the primary zone, inside the area bounded by the indicated temperature isolines (see Fig. 1), is approximately constant compared with the temperature distribution in the secondary and tertiary cutting zones, in which there is a temperature gradient of up to 5 °C/µm [13], [39], [42], [43]. ...
Preprint
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Thermal properties of work materials, which depend significantly on the change in cutting temperature, have a considerable effect on thermal machining characteristics. Therefore, the thermal properties used for the numerical simulation of the cutting process should be determined depending on the cutting temperature. To determine the thermal properties of the work materials, a methodology and a software-implemented algorithm were developed for their calculation. This methodology is based on analytical models for the determination of tangential stress in the primary cutting zone. Based on this stress and experimentally or analytically determined cutting temperatures, thermal properties of the work material were calculated, namely the coefficient of the heat capacity as well as the coefficient of thermal conductivity. Three variants were provided for determining the tangential stress: based on the normal stress calculated using the Johnson-Cook constitutive equation, based on the experimentally determined cutting and thrust forces as well as by directly calculating the tangential stress. The thermal properties were determined using the example of three different materials: AISI 1045 and AISI 4140 steel as well as Ti10V2Fe3Al titanium alloy (Ti-1023). With the developed FE cutting model, the deviation between experimental and simulated temperature values ranged from approx. 7.5–14.4%.
... Unfortunately, the infrared emissions may be easily blocked by the chips in material removal processes so typically this method is only adopted in orthogonal cutting. Another disadvantage of this method is the introduction of errors due to uncertainty in emissivity and surface characterization [18]. Calibration is required every time before the measurement of cutting temperatures. ...
Article
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In metal cutting, how to measure the tool tip temperature is always an issue. The highest temperature occurs at the contact surface between the tool and the chip, which is difficult for non-contact measuring methods such as the infrared thermal imaging technique. For other measuring methods, such as thermocouples, an additional small hole is required to be drilled before the sensor is able to be placed at the designated position, which greatly increases the cost. This paper presented a cutting temperature measurement with an ink-jet printed thermistor array. The printed sensor had high thermal index β, which possessed high temperature sensitivity, while its miniature dimension contributed to a fast response time. The ink-jet printing sensors can be made in advance so the setup time is short. Also, the sensors can be easily installed at different locations on the tool or the workpiece. In order to estimate the tool tip temperature, the finite element method (FEM) was used with the measured temperatures as inputs, which was known as an inverse heat conduction problem (IHCP). In order to increase computation efficiency to meet the requirement of online monitoring, the model order reduction method (MOR) was applied. In both non-cutting and cutting experiments, the temperature history could be easily estimated. In this study, the tool tip temperature was updated in 0.72 s, while the errors were only about 10% in non-cutting tests. This made it possible for online monitoring of cutting temperatures, while complex tool geometry and boundary conditions were considered.
... The signal was amplified and recorded by a digital oscilloscope. In principle, the sensitivity of this measuring method is independent of the emissivity of the object because the temperature is determined by the output ratio of each photodetector (Davies, et al., 2007). ...
Article
Tool flank temperature at various intervals after cutting ISO C45 steel through dry turn-milling is measured using a two-color pyrometer with an optical fiber in order to investigate the cutting characteristics. The complicated undeformed chip geometry, which depends on various parameters such as cutting tool diameter, nose radius of cutting tool, number of tooth, workpiece diameter, tool-work revolution speed ratio, depth of cut, feed per tooth, tool axis offset, and cutting distance, is analyzed and visualized by the 3D-CAD system. The effect of cutting parameters associated with material removal rate (MRR) such as workpiece diameter, revolution speed, and feed rate on tool flank temperature is investigated in this study. The analysis by the 3D-CAD system indicated that workpiece diameter affects tool flank temperature, and an increase in 10 mm in diameter results in approximately 40 °C higher temperature at any workpiece revolution speed due to the variation in undeformed chip geometry. The tool flank temperature increases as the feed rate and workpiece revolution speed increase because the cross-sectional cutting area of undeformed chip increases with workpiece revolution speed, and the cutting time during the engagement of each flute also increases with feed rate. Further, almost similar values are obtained between the tool flank temperature and MRR when both the workpiece revolution speed and feed rate are changed.
... Other temperature measurement methods cannot determine cutting temperature, but rather the temperature of the point where the detector was placed or the temperature field. Davies summarized various temperature measurement methods during machining [29]. ...
Article
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Turning of carbon fibre reinforced thermoplastic pipes is used for production of fluid ducts for the aerospace and oil industries. Although thermoplastics are chemically stable, the matrix could be affected by the heat introduced by the machining process. This paper presents how to measure cutting temperature using C/PEEK and C/PA12 material as examples. A suitable method based on a thermocouple circuit and electric conductivity of the carbon fibres is presented, including system calibration. Measurement uncertainties were established for this new method of calibration and measurement for both tested materials. The cutting temperature measurements were analysed by ANOVA and significant factors and its dependence on temperature were identified for further machining process optimization and determination of the predictive model equation. This mathematical cutting temperature model was estimated based on the measurements, and empirical coefficients were identified for selected statistically significant parameters for both composite materials. Because the measured temperatures were above the melting point, the machined surface, chips and structural changes of polymeric matrices were measured in order to prove heat affection.
... It is quite challenging to measure the temperature in the deformation region directly through experimental manners. Traditional methods, including infrared imager and embedded thermocouple, face the problem of low resolution and difficulty in practice [31][32][33][34]. From this point of view, numerical simulation is a more effective method to obtain the temperature field of the processing area. ...
Article
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Ultra-precision machining of single-crystal silicon can be realized by applying single-point diamond turning with micro-laser-assisted machining technology, through which the ductility of silicon can be enhanced. However, it is difficult to explain the role of temperature accurately in such technology in a traditional manner. In this study, numerical simulation technology was utilized to obtain the temperature distribution conquering the limitations of the traditional measurement method. Besides, a diamond grooving simulation model considering the temperature effect was developed using the smoothed particle hydrodynamics (SPH) algorithm. The shortcoming of the accuracy of calculation brought by applying the finite element method can be overcome effectively. By analyzing the evolutions of cutting force, the ductile-to-brittle transition behavior was distinguished. The comparison of the quantitative values of critical depths of cut between the simulations and grooving experiments corroborated the high accuracy of the as-established SPH model. In addition, the significance of temperature on ductile-to-brittle transition is successfully divulged. The simulation results demonstrate that the critical depth of cut of ductile-to-brittle transition increases in pace with an increase in temperature due to the thermal softening effect, indicating the enhancement of ductile response of the material. This study provides a novel method for the investigation of ductile-to-brittle transition mechanism and the optimization of processing parameters of single-crystal silicon.
... Most of the temperature measurements in friction systems use thermoelectric sensors called 'thermocouples' (Komanduri and Hou [1], Davies et al. [2]). A thermocouple in its simplest configuration consists of two dissimilar conductors (electrodes) joined in two junctions. ...
Article
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The present study investigates the performance of acicular grindable thermocouples based on a constantan wire / steel hollow cylinder construction. The experiments showed that the measuring junction electrical resistance, temperature–voltage characteristic, measuring junction rise time and signal noise standard deviation of the acicular thermocouples are comparable to those of conventional J-type thermocouples with bare wire diameter 0.25–0.5 mm. A pin-on-disc tribometer study of brake friction materials revealed that the acicular thermocouple involved in friction indicates up to 30% higher temperature than the contact temperature rise measured by infrared thermography. Another finding is that the infrared thermography contact temperature can be predicted with significantly higher accuracy by combining the acicular and conventional thermocouple techniques and taking the weighted sum of the respective temperatures.
... For example, Tapetado et al. [16] used a two-color fibre pyrometer and guided the fibre through the tool in order to measure the workpiece temperature close to the active zone. However, as Davies et al. [17] described in their related keynote paper, the key challenge is to measure the highly inaccessible contact temperatures in the secondary shear zone. ...
Article
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Numerical simulation of metal cutting with rigorous experimental validation is a profitable approach that facilitates process optimization and better productivity. In this work, we apply the Smoothed Particle Hydrodynamics (SPH) and Finite Element Method (FEM) to simulate the chip formation process within a thermo-mechanically coupled framework. A series of cutting experiments on two widely-used workpiece materials, i.e., AISI 1045 steel and Ti6Al4V titanium alloy, is conducted for validation purposes. Furthermore, we present a novel technique to measure the rake face temperature without manipulating the chip flow within the experimental framework, which offers a new quality of the experimental validation of thermal loads in orthogonal metal cutting. All material parameters and friction coefficients are identified in-situ, proposing new values for temperature-dependent and velocity-dependent friction coefficients of AISI 1045 and Ti6Al4V under the cutting conditions. Simulation results show that the choice of friction coefficient has a higher impact on SPH forces than FEM. Average errors of force prediction for SPH and FEM were in the range of 33% and 23%, respectively. Except for the rake face temperature of Ti6Al4V, both SPH and FEM provide accurate predictions of thermal loads with 5–20% error.
... Divers moyens sont disponibles pour la mesure de la température au cours de l'usinage (Davies et al., 2007;Longbottom & Lanham, 2005). Ceux-ci permettent d'analyser la température mise en jeu au niveau de l'outil, de la pièce usinée ou de l'interface outil/pièce. ...
Thesis
Dans les structures aéronautiques, les trous percés constituent des zones critiques à partir desquelles des endommagements peuvent s'initier en fatigue. En fonction des paramètres et des procédés de perçage employés, les industriels constatent des différences significatives de tenue en fatigue des structures percées. Ces travaux de thèse visent à apporter des éléments de compréhension à cette problématique industrielle, pour le cas pièces percées en AA2024-T351. Ils portent sur l'étude de configurations de perçage industrielles et se focalisent sur deux procédés de perçage : le perçage orbital qui est un procédé présentant de nombreux avantages économiques potentiels et le perçage axial qui est le procédé de perçage conventionnel. L'objectif des travaux est d'évaluer l'impact de la configuration de perçage sur la tenue en fatigue de la pièce percée, mais aussi sur l'intégrité de surface du trou percé. Cela doit permettre d'identifier les paramètres de l'intégrité de surface pilotant la tenue en fatigue et les paramètres majeurs du procédé de perçage contrôlant l'intégrité de surface. La première étape des travaux a été de mener des essais de fatigue afin d'évaluer la performance en fatigue de différentes configurations de perçage. Ceux-ci ont révélé des écarts significatifs de durée de vie en fatigue entre certaines configurations de perçage. La seconde étape a consisté à caractériser expérimentalement l'intégrité de surface des trous percés. Celle-ci a été guidée par un modèle éléments finis prédictif de la profondeur de matériau affectée en sous-surface du trou et de nouvelles méthodes d'analyse (comme la "HOCT") ont dû être envisagées pour certains aspects de l'intégrité de surface dû à la faible profondeur affectée. Cette campagne a montré l'influence prépondérante des aspects internes de l'intégrité de surface (écrouissage et contraintes résiduelles) sur la tenue en fatigue. Enfin, la dernière étape des travaux visait à étudier l'impact des paramètres du procédé de perçage sur l'intégrité de surface. Pour cela, un modèle éléments finis de coupe orthogonale a été développé. L'influence prépondérante de la géométrie de l'outil sur l'intégrité de surface a été montrée.
... The experimental research is aimed at measurement of cutting temperature using thermocouple, optical pyrometry, infrared thermography, thermo-chemical reaction, metallographic method, etc. A review of experimental methodology for determination of cutting temperature has been shown by Barrow, G.A. [19] and more recently by Davies et al. [20]. Ghodam [21] measured the temperature at the cutting edge of the coated and uncoated tungsten carbide tool with the tool-workpiece thermocouple method, as it is the easiest to set and cheaper as compared to other techniques. ...
Article
The research presented in this paper deals with the modeling and optimization of heat transfer problem in the machining process. An inverse heat transfer model based on the measured temperature at some point in the surface layer of the workpiece was used. The developed inverse model determines temperature and heat flux distribution for the selected machining conditions. By optimizing relationship between the intensity and duration of heat on the boundary of the workpiece, the optimum machining parameters are determined to achieve high productivity and quality at the same time. The solution of the inverse heat transfer problem is obtained by formulating an approximate well-posed problem by minimizing an objective function. Since it is an ill-posed inverse problem that is very sensitive to errors in the input data, special attention is required in order to ensure the conditions of uniformity and stability. Therefore, in this work we investigated the influence of the temperature measurement noise, the accuracy of knowledge of thermophysical properties of the material and the effect of possible instability of the numerical solution. Stability analysis of the inverse optimization problem is shown on the example of high performance grinding. The stability results were verified by a series of experiments.
... Davies et al. compared the measured temperature with the finite element method predicted temperature and found large difference in the results acquired by these two methods. They concluded that such difference is caused by two reasons, i.e., the error of modeling method and the error of non-deterministic factors in experiment [10]. Zhao and Liu [11] explored the effect of AlTiN coating on the cutting heat distribution coefficient and cutting temperature increment in orthogonal cutting of Inconel 718. ...
Article
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Minimum quantity lubrication (MQL) is an effective way to reduce the cutting temperature and tool wear. To reveal the effect of MQL on the wear of micro diamond tool, a calculation model for the cutting temperature of micro diamond tool under dry friction condition is established firstly by using the Fourier’s law of heat conduction. Regarding the boundary film as a layer of heat-conduction medium, a revised calculation model for the temperature distribution on tool rake face under MQL condition with different cutting fluids is further established. The predicted results indicate that low viscosity is beneficial to the wetting of cutting fluid on tool-chip contact interface, which can relieve the friction. The reduction of friction finally decreases the cutting temperature. Secondly, the cutting temperature–dependent wear volume of micro diamond tool is predicted by using the Usui wear rate model in response to different cutting fluids and different cutting distances. In dry cutting, the graphite wear of micro diamond tool prevails. However, the application of MQL can slow down the graphitization of diamond, so the wear of micro diamond tool visibly decreases. Finally, cutting experiments with different cutting fluids are performed to verify the established models. The experimental observations agree well with the theoretical prediction results. Such satisfactory consistency confirms that the cutting fluid with low viscosity can reduce the cutting temperature and inhibit tool wear effectively.
... The methods presented above are examples of different types that exist and have been addressed here due to their great application, advantageous characteristics, or growing and recent application. The aim of this work is not to review the temperature measurement methods (as performed by Da Silva and Wallbank [61] and Davies et al. [87]) but to present the most used techniques and those that have been gaining more space over time in the validation and feeding of temperature and heat flux prediction models. ...
Article
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The models of temperature prediction in manufacturing processes have advanced considerably in the last decades, either by applying numerical methods or by the development of techniques and methods of temperature measurement, which feed and compare the results of models. Associated with the advancement of prediction models is the improvement in the analysis of heat generation and distribution during materials machining. This work presents state of the art in research related to heat flux estimation in metal cutting processes using direct and inverse methods, through analytical, numerical, and empirical models. Pioneering and current research approaching the problem of estimating heat flux, as the main focus or means to predict the temperature distribution during the process, are reviewed. Its particularities, such as boundary conditions, techniques used, and innovations concerning previous works, are discussed. Therefore, this paper will present and detail different methods to estimate the heat flux during machining, aiming to help researchers identify the advantages and limitations in several cases discussed. The heat flux estimation using inverse methods can be more accurate with the development of data acquisition systems, reducing errors in measured temperatures during the process. In addition, multiphysics numerical simulations characterizing plastic deformation and heat transfer can be improved to help estimate the heat generated in machining.
... Thermocouples are commonly used for temperature measurements in the processes related to material removal from the surface of a component, including frictional and machining processes. Since the beginning of the 20th century, several thermocouple techniques have been developed and introduced to tribological applications, as reviewed by Kennedy [1], Komanduri and Hou [2] and Davies et al. [3]. ...
Article
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Acicular grindable thermocouples represent an interesting and prospective technique of temperature measurements at sliding contacts. This study aimed at the investigation of their reliability and accuracy as applied to the friction materials of various classes in contact with steel. The tests were conducted on a pin-on-disc tribometer under stationary and transient regimes. The experimental results were validated by comparing the temperature data obtained by the acicular thermocouple, conventional thermocouples and infrared thermography. It was found that the measurements conducted with the acicular thermocouples are test-retest reliable for copper and a brake pads material, whereas they are not reliable for a polyamide. The temperature rise measured with the acicular thermocouple deviates from that registered by infrared thermography by 7–15% for copper and 10–19% for the brake pads material.
... Targeting the cutting fluid along the rake and flank face alters the temperatures along the secondary shear zone and tertiary shear zone, as shown in Figure 1. However, experimentally measuring the machining generated temperatures, especially along the secondary and tertiary shear zones, is complicated and daunting [12]. A direct experimental approach for understanding the machining process's fundamentals is complicated as it involves a wide range of complex disciplines such as plasticity, metallurgy, heat transfer, fracture mechanics, fluid mechanics, etc. [13] . ...
Conference Paper
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Minimum quantity cutting fluid application is targeted upon the rake face and the flank face of the tool to improve the tool life and surface integrity. By strategically targeting/applying the cutting fluid on the tool rake and flank surfaces, the temperatures along the rake face and flank face are altered, thereby affecting surface machining-induced residual stresses. The magnitude of temperature alteration and thereby the machining-induced residual stresses can be affected by the amount of targeted cutting fluid and the composition of the targeted cutting fluid. In this paper, the authors use a numerical finite element approach to understand the effects of the strategically targeted cutting fluid on the flank face improves the sub-surface residual stresses by reducing the tool-tip machining temperatures when machining AISI 1045 annealed steel with an uncoated cemented carbide tool. The machining-induced residual stresses generated from the finite element model have shown that the temperatures near the tool tip reduce by targeting cutting fluid on the flank face. The targeted cutting fluid reduced the machined workpiece temperatures and also assisted in cooling the cutting tool from the flank and rake side.
... The temperature in the cutting zone was measured using thermal imaging [35,36]. The tool temperature measurements were performed during orthogonal turning of disk-shaped workpieces, as shown in Fig. 4 (left). ...
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Lead has traditionally been added to brass alloys to achieve high machinability, but the exact mechanisms at work are still debated. Lead-free brass alternatives could be developed if these mechanisms were better understood. Accordingly, machinability characteristics were investigated for two brass alloys with similar mechanical properties and phase composition, but with very different machining characteristics because one has 3 wt.% lead (CuZn38Pb3) while the other has only 0.1 wt.% (CuZn42). The effect of the lead was investigated using infrared temperature measurement, electron microscopy, secondary ion mass spectroscopy, quick-stop methods, and high-speed filming. Neither melting of lead nor its deposition on the tool rake surface takes place during machining thus confirming its limited lubrication and tribological effects. Instead, the main role of lead is to promote discontinuous chip formation. Lead deforms to flake-like shapes that act as crack initiation points when the workpiece material passes through the primary deformation zone. This effect prevents the development of stable tool–chip contact, thus lowering cutting forces, friction, and process temperature.
... During these processes, a large amount of heat is generated, as a result of friction caused by shear force, being estimated that more than 90% of the mechanical work applied to the workpiece is transformed in thermal energy, overheating the cutting tool in a very small zone (cutting edge) and leading to thermo-elastic deformations in the tool [5][6][7]. As a result, such high temperatures (typically ranging from several hundreds to thousand degrees Celsius) strongly influence tool wear, tool life, workpiece surface integrity and quality, and chip formation mechanisms that may lead to tool deformation, fracturing and formation of built-up edge, less dimensional accuracy of the product, damage of the workpiece surface, and development of microcracks at the surface, consequently leading to high operating costs and reduction of the end product quality [4,8,9]. Based on the orthogonal cutting process evaluation, it is possible to define three zones where heat is generated, as depicted in Fig. 1. ...
Article
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During machining processes, a large amount of heat is generated due to plastic deformation, in a very small area of the cutting tool. This high temperature strongly influences chip formation mechanisms, tool wear, tool life, and workpiece surface integrity and quality. In this sense, knowing the temperature at various points of tool, chip, and workpiece during machining processes is of utmost importance to effectively optimize cutting parameters, improve machinability and product quality, reduce machining costs, and increase tool life and productivity. This paper presents a review of the various methods for temperature measurement and prediction in machining processes, being the different methods discussed and evaluated regarding its merits and demerits. The most suitable method for a given application depends on several aspects, such as cost, size, shape, accuracy, response time, and temperature range. Lastly, some future perspectives for real-time cutting temperature monitoring in the scope of Industry 4.0 and 5.0 are outlined, as well as being presented a new field of tools capable of measuring and controlling cutting temperature, called smart cutting tools.
... Hence, knowledge of the actual conditions in the grinding arc À in particular temperatures and forces À is of import with regard to surface integrity of the machined part or wear of the grinding tool among others. The development of techniques for the survey of grinding processes has a long history [52,119,120]. In the beginning of this process machine tools and in particular workpieces were equipped with measurement techniques. ...
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Because of their many applications, including automotive, aeronautics, optics, and so forth, demand for grinding tools sees unabated growth. But the energy and resource intensive nature of their manufacture leads to questions of sustainability. This paper details how recent developments in basic tool technology (structure, binder, abrasives) is increasing tool and abrasive resilience while reducing production inputs. The advent of smart grinding tools involving aspects of surface engineering, process hybridization, and process monitoring is also discussed. The paper concludes with an outlook of further energy savings, tool recycling and uses of additive manufacturing with the aim of achieving long-term sustainability.
Article
The present study introduces a novel model for the prediction of temperature in a cutting tool while the effects of all three deformation zones are considered. The model considers the effect of cutting-edge radius and the third deformation zone for the first time in the literature in terms of temperature prediction using thermo-mechanical approach with dual-zone friction model. The material behavior is defined by the Johnson-Cook constitutive model. For the calculation of heat flux on the rake and flank faces, a dual-zone model was used. The temperature distributions at the tool-chip and tool-workpiece boundaries were determined analytically, and the temperature distribution inside the tool was calculated using the Finite Difference Method. In order to verify the model, experiments were performed with AISI1050 steel and Al7075 workpiece materials using tungsten-carbide cutting tools. A good agreement is observed between the model predictions and the test results. This study also examined the effects of cutting-edge geometry and cutting conditions on cutting temperature, which can be used in optimized selection of cutting parameters and tool geometry.
Chapter
To achieve high productivity and precision of machining shaft-like workpieces, many methods have been developed for in-process monitoring. This paper presents a novel monitoring method based on On-Rotor Sensing (ORS) techniques. Main vibration mechanisms of turning a shaft on a lathe were studied analytically, which shows great changes in vibration modes with turning operations. Experimental studies are then performed to identify the informative vibration features for monitoring and on-line diagnostics. The results show that the vibration perceived by ORS approach contains rich information for in-process monitoring. In particular, vibration characteristics in the frequency domain can sensitively distinguish between different depths of cut, feed lengths and tool wear status, paving fundamentals for in-process quality control. In addition, it also allows instable cuts to be indicated at infant stages, providing feedbacks for cutting parameter tuning. Therefore, this novel ORS based monitoring method paves a genuine data aggregation approach for Internet of Things (IoT) enabled intelligent manufacturing.
Article
The BTA deep hole drilling process is used to machine deep bores with a large diameter. The cutting process, consisting of the material removal by cutting edge and the surface burnishing by the guidepads influence the surface of the bore. To separate the impact of the cutting edge from that of the guidepads on the surface of the bore and the subsurface zone an experimental model setup in analogy to the BTA process was developed. This paper covers the differences to the conventional BTA deep hole drilling, the experimental boundary conditions and the measurement of the surface roughness. The results are compared to previous analysis of the surface integrity of BTA deep hole drilled specimens. Furthermore, conclusions about the process forces are drawn from the documented loads occurring for the machine axes. In part 2 of this study, the surface integrity of the specimens is further analyzed using destructive and non-destructive methods.
Article
Heat flux during machining has received extensive attention due to its importance for understanding the cutting mechanism and promising prospects on intelligent manufacturing. Research on heat flux estimation by inverse heat conduction methods faces many challenges, including measurement error amplification, stability of the methods, and limitations for applications. In this paper, we introduce a long short-term memory (LSTM) based encoder-decoder (ED) scheme in online estimation of the heat flux imposed at the tool-chip region during turning. The math-physical model and finite element model are established to generate training datasets. Numerical tests using simulated heat flux and temperature data representing different machining conditions are carried out to evaluate the method performance. Compared with other artificial intelligence methods such as multilayer perceptron, convolutional neural networks and LSTM, the LSTM-ED model performs better at all tested noise levels (1≤σ≤20K) with acceptable time cost for online process. Effects of the location and number of sensors on the accuracy of heat flux estimations are also investigated. Experimental validations based on cutting temperature measurements by five thermocouples located in the insert are conducted. Both numerical and experimental tests indicate the potential of the LSTM-ED method for online heat flux monitoring in scientific research and industrial production.
Thesis
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Die Ermüdungsfestigkeit und Verschleißbeständigkeit eines Bauteils hängt maßgeblich von dessen Oberflächenmorphologie ab. Neben einer niedrigen Rauheit ist daher für eine Vielzahl technischer Anwendungen eine verfestigte Randschicht vorteilhaft. Metastabile austentische Stähle können hierzu nach der spanenden Bearbeitung durch mechanische Verfestigungsprozesse wie bspw. Kugelstrahlen nachbehandelt werden. Die Randschichtverfestigung resultiert dabei aus einer Überlagerung von Kaltverfestigungsmechanismen und verformungsinduzierter Martensitbildung. Kryogenes Drehen als Endbearbeitung kann, je nach Prozessauslegung und Anforderung an die Bauteiloberfläche, durch die integrierte Randschichtverfestigung einen nachgelagerten separaten Verfestigungsprozess obsolet machen. Umfangreich untersucht ist hierbei der Einfluss der Schnittparameter sowie der Kühlstrategie auf die Prozessgrößen und die Oberflächenmorphologie. Generell begünstigen niedrige thermische und hohe mechanische Lasten die verformungsinduzierte Martensitbildung und somit die Randschichtverfestigung. Im Rahmen dieser Arbeit wurde zunächst der Einfluss des Werkstoffs und der Werkzeugeigenschaften untersucht. Dabei zeigte sich, dass sich trotz chargenbedingten Unterschieden in der chemischen Zusammensetzung eine robuste Randschichtverfestigung realisieren lässt und sich die thermomechanische Last und die Oberflächenmorphologie in Abhängigkeit der Werkzeugeigenschaften gezielt einstellen und verbessern lassen. Weiterhin wurde der Martensitgehalt in Abhängigkeit der beim kryogenen Drehen vorherrschenden thermomechanischen Last modelliert. Abschließend wurde die Oberflächenmorphologie in einem neuartigen Ansatz durch zwei konsekutive Bearbeitungsschritte verbessert.
Article
The surface integrity of components is decisive for their fatigue strength and is significantly influenced by applied machining processes. Particularly in drilling, the used coolant strategy affects the process stability and the surface quality produced due to its contribution to chip evacuation and the cooling and lubricating effect of the cutting zone. In this article, different cooling lubrication strategies are investigated in single-lip deep hole drilling of quenched and tempered AISI 4140 steel with respect to their effects on occurring thermomechanical loads and the resulting surface integrity parameters. The results for drilling with cutting oil, water-based emulsion and minimum quantity lubrication (MQL) under varying cutting parameters are analyzed with a focus on their impact on the bores’ subsurface microstructure and resulting hardening generated in the bores‘ subsurface.
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The cutting temperature is essential for phenomena understanding and quality improvement in metal cutting while its in-situ online measurement is still a challenge. This paper presents a near-infrared fiber-optic multi-spectral method for in-situ online cutting temperature measurement. Using thermal radiation spectrum for temperature measurement, the method optimizes the lower limit of temperature measurement to 150 °C while improving accuracy. The calibration shows that in the range of above 250 °C, the average relative error of temperature measurement is stable below 0.5%. The titanium alloy cutting experiments are carried out. In-situ online measurement of tool temperatures in dry/wet cuttings are realized using the self-developed system. The influence of cutting parameters on cutting temperature is studied, and the real-time response of the temperature measurement system to the cutting state is verified. As for industrial application, the capability of the system in heavy-duty turning is proved by railway wheelsets turning experiments. Tool wear experiments are conducted, and a positive correlation between the cutting temperature and tool wear is revealed. Tool wear status recognition is realized based on cutting temperature by sparse autoencoder and k-means clustering, and a recognition accuracy of 97.3% is achieved. These results indicate promising prospects in cutting mechanism research, machining status monitoring and industrial applications, empowering the advancement of intelligent manufacturing and industry 4.0.
Article
In this paper, a synchronous acquisition system of milling temperature and milling vibration was established to measure the data of milling temperature and milling vibration. Based on grey correlation theory, the influence of milling parameters and milling vibration on milling temperature was analyzed. It is found that the grey correlation degree between milling temperature and milling parameters and vibration is above 0.70, indicating that milling parameters and vibration have great influence on temperature. In addition, the GM (0, N) grey prediction model of milling temperature on milling parameters and milling vibration was established, and the correlation coefficient of the model was above 0.8, indicating that the reliability of the model was high, and the correlation between milling temperature and milling vibration signal was high.
Article
The wear of cutting tools is one of the main current problems, especially when it comes to new materials called "difficult to machine" or with high added value. Tool wear is caused by extreme thermomechanical loads applied to the contact areas of tool chips and tool parts. During milling, turning or drilling operations, for example, large deformations, high deformation rates and high temperatures can be observed near the surface of the cutting tool. The objective of our work is to respond to the problem of abrasion wear by developing a predictive tool, based on knowledge of the physical and tribological mechanisms of workpiece-tool contacts, allowing us to quantitatively estimate the wear of the tool and its service life. To achieve this, we base our approach on previous studies carried out in the field of machining and metalworking. The modeling work was first applied to the wear case, then extended to the study of the crater wear occurring on the cutting face. By taking into account the mechanical load applied and the geometry of the contacts involved (plane-plane contacts), we have developed a two-dimensional approach in orthogonal cut configuration.
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Despite the prevalence of machining, tools and cutting conditions are often chosen based on empirical databases, which are hard to be made, and they are only valid in the range of conditions tested to develop it. Predictive numerical models have thus emerged as a promising approach. To function correctly, they require accurate data related to appropriate material properties (e.g., constitutive models, ductile failure law). Nevertheless, material characterization is usually carried out through thermomechanical tests, under conditions far different from those encountered in machining. In addition, segmented chips observed when cutting titanium alloys make it a challenge to develop an accurate model. At low cutting speeds, chip segmentation is assumed to be due to lack of ductility of the material. In this work, orthogonal cutting tests of Ti6Al4V alloy were carried out, varying the uncut chip thickness from 0.2 to 0.4 mm and the cutting speed from 2.5 to 7.5 m/min. The temperature in the shear zone was measured through infrared measurements with high resolution. It was observed experimentally, and in the FEM, that chip segmentation causes oscillations in the workpiece temperature, chip thickness and cutting forces. Moreover, workpiece temperature and cutting force signals were observed to be in counterphase, which was predicted by the ductile failure model. Oscillation frequency was employed in order to improve the ductile failure law by using inverse simulation, reducing the prediction error of segmentation frequency from more than 100% to an average error lower than 10%.
Article
The rapid development forms a new transition of information technologies to offer an intelligent manufacturing. The manufacturer has revolutionized the stages of product lifecycle including process planning and maintenance for the early detection of potential system failures and proactive management. Technological advancements including big data, the cloud, and the Internet of Things have applied digital-twin for industrial practice. It has low-power wireless-enabled devices to play a vital role in various industrial automation systems such as industry logistics, portable equipment, and intelligent wireless monitoring. It is evident that industrial manufacturers are nowadays aiming to transform the machine into fully automated systems that not only control the operation of the equipment but also try to meet the demand of future markets effectively. One of the challenging issues in the automation of the machinery process is the deployment of reliable systems to analyze the machinery condition such as fault diagnosis. Thus, this article proposes a digital-twin-assisted fault diagnosis using deep transfer learning to analyze the operational conditions of machining tools. Moreover, this proposed system has developed an intelligent tool-holder that integrates a k-type thermocouple and cloud data acquisition system over the WiFi module. The analytical study proves that this intelligent tool-holder provides better accuracy to demonstrate the optimization of milling and drilling operations of cutting tools.
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A review is presented on high temperature measurement technology based on sapphire optical fiber. This review paper focuses on the sensing theory, sensor structures and sensing performances of different sapphire fiber sensors. Firstly, there is discussion on pyrometer made from sapphire fiber and description on its corresponding sensing properties. Secondly, there are summary on sapphire fiber Bragg grating (SFBG) inscribed by different methods for high temperature measurement. Thirdly, there are analysis on sapphire fiber sensors based on Fabry Perot (FP) interference with different structures. All above, subsequently, lead to the discussion on microwave interferometry and Raman scattering-based sapphire fiber sensors. Then a sensing performance comparison of sapphire pyrometers based on different detection principles are discussed. On the premise of all above, a future prospect and development trend of high-temperature sapphire fiber sensor are addressed as well.
Thesis
Cylindrical machining processes are widely used in industry to achieve better dimensional and geometrical tolerances and finer surface finish on cylindrical workpieces. Hard turning is utilized to machine hardened steels for large bearing rings and finish boring is used to machine cylinder bores during automotive engine block production. Workpiece temperature is critical for cylindrical machining processes. In hard turning, high machined surface temperature leads to the formation of white layer, reducing the workpiece fatigue life. In finish boring, thermal expansion due to workpiece temperature rise causes bore cylindricity errors, leading to engine performance issues. Besides thermal expansion, other factors like cutting force, spindle, and fixture/clamping also affect the bore cylindricity in finish boring. This dissertation studied the cylindrical machining workpiece temperature through both experiment and modelling and identified bore cylindricity error sources in finish boring. Firstly, two experimental methods were developed to measure machined surface temperatures in hard turning. The first method, based on a tool-foil thermocouple, estimated the machined surface temperature using a metal foil embedded in the workpiece to measure the tool tip temperature. The second method used a thermocouple embedded in the tool with its tip continuously sliding on the machined surface behind the cutting edge. The inverse heat transfer method was applied on a three-dimensional thermal model to find the machined surface temperature near the cutting edge. These two methods, although based on distinct approaches, gave correlated predictions in hard turning tests, indicating both to be feasible for the measurement of hard turning machined surface temperatures. Secondly, four finite element method (FEM) models, namely the advection model, surface heat model, heat carrier model and ring heat model, were studied to predict the workpiece temperature in finish boring. Cylinder boring experiments were conducted to measure the workpiece temperature and evaluate the capability of four models in terms of accuracy and efficiency. Results showed good correlations between model-predicted and experimentally- measured temperatures. Advantages and disadvantages of each model were discussed. For studying detailed cylinder boring workpiece temperature, it was suggested to use the ring heat model to estimate the moving heat flux and the heat carrier model for local workpiece temperature calculation. Thirdly, experimental and FEM analysis was combined to identify the bore cylindricity error sources in finish boring. Experiments were conducted to measure the workpiece temperature, cutting and clamping forces, spindle error, and bore shape. FEM analysis of the workpiece temperature, thermal expansion, and deformation due to cutting and clamping forces was performed. The coordinate measurement machine (CMM) measurements of the bore after finish boring showed the 5.6 micrometer cylindricity and a broad spectrum from 2nd to 10th harmonics. The FEM revealed effects of workpiece thermal expansion (1.7 micrometer cylindricity), deformation due to cutting force (0.8 micrometer cylindricity), and clamping force (1.9 micrometer cylindricity) on the finished bore and the dominance by the 1st to 3rd harmonics using the three-jaw fixture. The spindle synchronous radial error motion (3.2 micrometer cylindricity) was dominated by 4th and higher order harmonics and matched well with the high (above 4th) harmonics in CMM measurements (2.9 micrometer cylindricity). The spindle error was found to be the dominant error source for bore cylindricity in finish boring. The experimental methods, FEM models and approaches developed in this dissertation provide better understanding of cylindrical machining processes and are useful for optimization of the process parameters.
Article
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The paper presents an experimental-analytical method for determination of temperature in the cutting zone during the orthogonal turning of GRADE 2 titanium alloy. A cutting insert with a complex rake geometry was used in the experiments. The experimental part of the method involved orthogonal turning tests during which the cutting forces and the chip forming process were recorded for two different insert rake faces. The analytical part used a relationship between the cutting forces and the temperature in the Primary Shear Zone (PSZ) and the Secondary Shear Zone (SSZ), which are described by the Johnson-Cook (J-C) constitutive model and the chip forming model according to the Oxley’s theory. The temperature in the PSZ and SSZ was determined by finding the minimum difference between the shear flow stress determined in the J-C model and the Oxley’s model. Finally, using the described method, the relationship between the temperature in the PSZ and SSZ and the rake face geometry was determined. In addition, the temperature in the cutting zone was measured during the experimental tests with the use of a thermovision camera. The temperature distribution results determined experimentally with a thermovision camera were compared with the results obtained with the described method.
Chapter
Die Zerspanung von CFK und artverwandten Faserverbundkunststoffen erfordert aufgrund von deren Orthotropie eine Erweiterung der für isotrope Werkstoffe bekannten Grundlagen und Modelle. Entsprechend werden der Orthogonalschnitt ergänzt sowie die Eingriffsverhältnisse und Kinematik beim Fräsen, Sägen, Bohren und Schleifen im schrägen Schnitt mit schaft- und scheibenförmigen Werkzeugen beschrieben. Die technologischen Grundlagen der FVK-Zerspanung werden getrennt für die Verfahren mit definierter und mit undefinierter Schneide erläutert. Behandelt werden jeweils der Trennmechanismus, die im Trennprozess erzeugten Spanpartikel und Emissionen, die Kräfte, die Energieumsetzung und Temperaturen, die Werkzeugverschleißmechanismen sowie die mit Zerspan- und Schleifverfahren herstellbare Werkstückqualität. Zur Analyse von FVK-Zerspanprozessen werden spezifische Versuchstechniken und Messmethoden vorgestellt.
Article
The cutting temperature plays an important role in the machining process. Research on the real-time monitoring of cutting temperature and its effect on tool wear still faces many challenges. In this paper, a fiber-optic two-color pyrometer is proposed to obtain temperature of cutting edge during turning at real-time. The effects of the cutting speed, cutting depth and feed rate on the variation of cutting edge temperatures are investigated. Intermittent cutting experiments are performed to verify the effectiveness and dynamic responsiveness. The processed inserts show good durability. The cutting temperature change and its effect on tool wear are also investigated.
Article
In-process control of machining operations allows to develop strategies to modify and improve the surface integrity of manufactured components and thereby enhancing their performance and lifetime. These control strategies require reliable real-time data like cutting forces, process temperatures and tool wear. In this work, a wear-resistive thin-film sensor is developed to measure temperature of the cutting tool surface during machining. A multi-layer sensor system is applied on the tool surface by physical vapor deposition (PVD). The tool-sensors are subsequently tested for their functionality and durability in turning operations of AISI 4140q&t steel.
Article
This study investigates the dynamic temperature behaviour around a melt pool in metal-based powder bed fusion using a laser beam (PBF-LB/M) to clarify the influence of the associated morphological changes of the metal powder experimentally. Gas-atomized 18Ni (300-grade) maraging steel powders were processed by PBF-LB/M while high-speed photography with a two-colour radiometric thermal imaging system that was employed to correlate the temperature with melt pool behaviour. In addition, the cooling rate of the melt pool was measured directly using the dynamic temperature distribution. The temperature distribution of the melt pool was influenced by the morphological changes of the metal powder induced by physical and thermal interactions, and the melt pool exhibited an asymmetric temperature distribution in the direction parallel to the laser scan. The significant factors were droplet cohesion at low melt pool temperatures, remaining heat energy from previous laser beam irradiation, and the heat conduction inside the melt pool. The laser beam incident on the metal powder was primarily characterized by two modes: direct heating induced by laser beam irradiation and heat conduction through the single track, droplets, and substrate. In addition, the dynamic temperature behaviour provided a direct explanation for the cooling rate, the values of which ranged from 0.1 to 0.9 × 10⁶ K/s owing to the self-cooling induced by PBF-LB/M.
Article
Excessive machining temperature, also called overheating phenomenon, remains a significant influencing factor that determines the lifetime of aeronautics safety components. During metal cutting, the thermal partition in the different shear zones can vary, depending on kinematic process parameters and cutting edge geometry. In order to identify the temperature gradient beneath the machined surface, a new methodology has been developed with the use of a single wire thin thermocouple. Indeed, the miniaturization of the K-thermocouple allows to measure in the primary shear zone temperature. Orthogonal cutting tests are performed at several uncut chip thickness to reproduce the milling chip shape, and the impact of rake angle uncut chip thickness is underlined. Experimental results show that less than 15% of total cutting power is transferred into the machined surface with an unworn tool. This proportion decrease with the reduction of rake angle. Cutting energy in primary shear zone is hardly evacuated by the chip for thin uncut chip thicknesses.
Article
This keynote paper mainly focuses on advancements of machining technology and systems for enhanced performance, increased system integration and augmented machine intelligence, critically hinging on new sensors, sensor systems and sensing methodologies being robust, reconfigurable and intelligent, while providing direct adoption and plug-and-play use in industrial practice. One chief novelty is given by the key enabling technologies of Industry 4.0 where integration of sensing systems in manufacturing plants is a cornerstone for transforming conventional manufacturing concepts into digital manufacturing paradigms. Application examples to industrial processes, future challenges and coming trends in machining monitoring are shown.
Presentation
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Acicular thermocouples represent a technique of temperature measurement at a sliding contact which provides continuous measurements under intensive wear conditions. The study investigates them as applied to brake friction materials. The temperature determination accuracy can be increased by combining the acicular and conventional thermocouple techniques.
Chapter
High temperatures during abrasive cutting lead to increased harmful gas emissions released into the environment, intensified cut-off wheel wear, microstructural changes in the machined material, and occurrence of thermal flaws. Temperature measurement in abrasive cutting is difficult due to the small size of the heated area (only tenths of mm2), high temperatures (above 1000°C), continuous change of the conditions within one cut-off cycle, large temperature gradient (more than 200°C), high cutting speed (above 50 m/s) and high mechanical load. The infrared thermography (IRT) application for thermal control of elastic abrasive cutting have been studied. The performed thermal measurements have been verified with the results obtained from the temperature models of workpiece, cut-off wheel, and cut piece depending on the conditions in elastic abrasive cutting of two structural steels C45 and 42Cr4. The parameters of effective abrasive cutting have been determined by applying multi-objective optimization.
Article
In this paper, a universal method is proposed to accurately identify wheel state during grinding brittle materials. In contrast with conventional methods relying on adequate repetitive experimental data under the same process conditions, only history acoustic emission (AE) data in the same life cycle of a grinding wheel are needed for current wheel state identification. During grinding process, AE spectra samples are acquired sequentially on a series of nodes with equal interval. Samples on each node are categorized into the same class of wheel state. In the theoretical part, AE spectrum is proved to be suitable for feature representation of the degradation of wheel condition. Linear discriminant analysis is used to project AE spectra samples into a two-dimensional feature space, and the changes of the projection gives a clue to the evolution of wheel state. Two types of commonly used diamond wheels for optical surface grinding, which are straight wheel and cup wheel, were used to verify the general applicability of the method. The experiments were carried out on different machine tools and the two wheels also possessed different degradation process, yet for all of them, the evolution of wheel state can be accurately identified. It was proved that the proposed method can adaptively trace wear stage change of diamond grinding wheel.
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High-speed steel (HSS) tools account for 20 percent of the cutting tools materials’ global market. This is due to both their significant toughness and resistance to cracking, compared to cemented carbides. Covering steel tools with hard coatings clearly improves their mechanical properties, wear resistance, and significantly increases their durability. Physical vapor deposition methods are preferred for coating metal substrates, as they allow low temperature deposition. The most widely deposited coating materials are carbides, nitrides, and borides. They are combined with softer ones in the multilayer structure to promote increased resistance to cracking and delamination in comparison to monolayered structures. In this paper, the M2 steel end mills were coated by (TiBx/TiSiyCz) x3 multilayer by the pulsed laser deposition method. Coated and uncoated tools were tested in the cylindrical down milling of AISI 316L steel. Components of the cutting force and temperature generated in the machined area during dry milling were measured under two variants of operating conditions: V1 and V2. Tool wear mechanism was examined using scanning electron microscopy (SEM), accompanied by EDS analysis of worn areas. It was found that milling with higher speed (variant V2) is accompanied by lower cutting force components and a lower temperature generated in cutting area. The presence of the coating allowed lower cutting forces and temperature in the case of variant V1. The temperature measured during milling did not exceed 200 °C. The SEM observation of the edges of cutting tools indicated that the main mechanism of wear for both types of tools was abrasion. The built-up edge formation was observed in the case of tools tested at the V1 cutting parameters variant. It was assumed that it was the reason for higher cutting forces measured during milling according to this variant. The chemical composition of built-up edges was different for coated and uncoated tools. Tribo-chemical reactions were responsible for the reduction of the cutting force and temperature components observed during milling with a coated tool at V1 variant. Boron and titanium were the elements of the coating that enabled the tribo-oxidation reactions thanks to which friction was reduced. Our results show that this beneficial effect occurs with (TiBx/TiSiyCz) x3 coated tools, but can easily be lost with inadequately selected cutting parameters.
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Adequate setting of the boundary conditions for the heat equation when modeling the temperature distribution in the cutting tool is one of the key points. The boundary conditions on the tool surfaces can be divided into two groups: conditions that describe heat losses (heat exchange with the environment) and conditions that characterize the heat source that heats up the tool (heat flux from the cutting zone). Additional complexity in modeling is provided by the fact that during cutting the surface on which the heat source acts changes, for example, due to wear on the flank surface. In this paper, a method is proposed for measuring the power of a heat source acting on the flank surface. The hardware of the method includes a sensor equipped tool and specially manufactured inserts that imitate the geometry of worn flank surface. In turn, the software is based on the method of solving the inverse heat conduction problem in metal cutting, which allows restoring the heat flux flowing into the tool by measuring temperature with sensors installed in the toolholder. The experimental plan included inserts with negative and positive rake, different cutting speeds (190, 235, 280 m/min), and feeds (0.15, 0.3, 0.45 mm/rev).
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A compensating circuit which facilitates the use of the tool-work thermocouple for interface-temperature measurements is presented. The IR drop due to the flow of thermoelectric current in a closed circuit is used to nullify the parasitic emf introduced by dissimilar lead materials attached to the cutting insert. Conditions necessary to achieve complete compensation are explained and test results indicating the reliability of the method are given.
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Two new methods of measuring cutting temperatures have been evaluated. The first is a radiation technique using a lead-sulfide cell. The cell is arranged to sight through a small hole drilled in the work material sensing radiation from the shear plane and clearance face of the tool. Peak temperatures in these regions have been obtained but shear-plane temperature distributions could not be determined successfully. The second technique uses a 0.005-in. single wire imbedded in the side of a workpiece as a thermocouple. With orthogonal cutting the tool passed beneath the wire so that the wire passed up the tool face still imbedded in the chip. By this method it was possible to determine the temperature field throughout the chip and work. These temperature fields have been compared to theoretical predictions and show only fair agreement. The lack of agreement is due partially to the simplifying assumptions of orthogonal cutting and a true geometric shear plane necessary for theoretical solution. The necessity of locating the thermocouple junction on the side of the work introduced errors from side flow of the chip and certain other edge effects. The iteration procedure of Trigger and Chao has been extended to tools of any rake angle and simplified by use of a conducting-paper electrical analog.
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The cutting performance of CBN tools-CBN-rich type and ordinary one-for high-speed end milling of hardened steel is investigated. The availability of TiAlN-coated carbide tools in low-speed hardmilling is also examined. In dry cutting of hardened carbon steel with the ordinary CBN tool, the cutting tool temperature θ_α rises rapidly with the increase of cutting speed v, and θ_α reaches approximately 850℃ at v=600m/min. In the case of the CBN-rich tool, the cutting temperature decreases by 50℃ or more because of high thermal conductivity. The hardness of workpiece has great influence on the cutting temperature. The TiAlN-coated carbide tool is sufficiently applicable to low-speed hardmilling.
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The temperature field in the workpiece during surface grinding has been measured using a charge-coupled device (CCD) based infra-red imaging system. Infra-red (IR) radiation measurements, at high spatial and temporal resolution, have been made along a side of the grinding specimen to estimate workpiece surface and sub-surface temperatures. By grinding along a taper, with a continuously increasing depth of cut, the variation in grinding temperature with material removal rate has been obtained. These measurements have correlated well with those made in conventional constant material removal rate grinding tests. The location and values of highest temperature, including temperature gradients, have been identified. Implications of the measurements for validating thermal models of grinding, and predicting the onset of thermal damage in the workpiece are discussed.
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The measurement of the temperature field at the tool-chip interface in machining has been demonstrated. The key elements in the measurement technique are the use of an optically transparent sapphire tool, which has enabled direct images of the tool-chip contact area in the infra-red to be obtained at high spatial and temporal resolution; and radiation intensity measurements in two wavelength windows which have enabled the temperature field to be accurately derived from these intensity values. The principal characteristics of the temperature field such as the variation of temperature with position along the interface and the location of the region of highest temperature are identified. The implications of this measurement to our understanding of the tribology of the tool-chip interface and machining process models are briefly discussed.
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It is shown that the mean temperature in the contact zone in the high speed polishing of glass with a diamond bearing tool is higher by a factor of about four than with the classical grinding method. An adequate connection is established between the power utilized in polishing and the temperature in the polishing zone. It is established that a specific level of power consumption for polishing and a corresponding value of the mean temperature are required in order to raise output and to obtain the best surface roughness, which can be attained by increasing the pressure to a certain limit or by decreasing the consumption of coolant (e. g. water), i. e. , polishing should be 'hot'.
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A study of the effect of land wear upon the interface temperature between a carbide tool and an AISI 1015 steel workpiece is presented. The wear lands were ground on the tools to eliminate the effects of cratering and to produce uniform wear lands. The tool-work thermocouple technique was used to measure the interface temperature. A calibration of the thermocouple was obtained through the use of a technique suggested by Backer and Krabacher. The results at all feeds and speeds indicate that a wear land of 0.010 in. produces a lower interface temperature than a sharp tool. When the wear land increases beyond 0.010 in. to 0.020 and 0.030 in. the temperature again rises. Studies of the variation of the chip thickness ratio with wear land indicated that the greater the land wear the lower the chip thickness ratio.
Article
The tendency of heat checks and cracks to form in the workpiece is shown to be strongly dependent upon work speed. The durability of the cutting edges of tools is shown to be affected by the work speed during sharpening. Based on the rubbing-grain hypothesis, the “theory of heat conducton” is applied to the grinding process to show that lower surface temperatures occur when grinding is done at high work-surface speed.
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An analytical and experimental investigation of heat transfer to, and the resulting temperature distribution in, a metal-cutting tool during orthogonal cutting is described. A rectangular parallelepiped-shaped tool is postulated and a product solution developed for the temperature distribution under the conditions of a continuous uniform release of heat over the tool-chip contact area and heat loss from each side arbitrarily specified. To test the validity of this solution two high-speed lathe tools with 0-deg and 15-deg back-rake angles were uniquely instrumented with thermocouples located in the tool bodies at selected distances from the cutting edges. Representative temperature records obtained during dry orthogonal cutting of SAE 1020 steel with these tools are presented. Extrapolation of temperature measurements to the center of the tool-chip contact area gave values for the average tool-chip interface temperatures which agree quite closely with results of other investigators. Average heat rates to the tools are determined and the applicability of the product solution is discussed.
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Using metallographic and microhardness techniques, temperature distributions have been determined in twist drills. The methods rely on the fact that certain high speed steel materials exhibit microstructural changes when subjected to temperatures greater than 600°C. Quick-stop specimens have also been obtained to study the metal flow patterns over the drill flutes. These results have been used to comment on the different wear mechanisms that affect the performance of a twist drill. Preliminary results show that bulk plastic flow occurs near the margin of the drill where the temperatures are in the vicinity of 900°C when machining AISI 1045 steel at 40 m/min.
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This paper compares experimental measurements and model-based simulations of cutting temperature, force, and chip thickness for machining of aluminum. Cutting temperatures were measured using high-speed infrared videography, and forces were measured using a 3-axis dynamometer. Results reported here are for machining 7075-T651 aluminum at cutting speeds from 100 m/min to 276 m/min. This paper focuses on comparing finite-element modeling simulations to the experimental data and discussing limitations of experimental measurements and simulations in capturing process behavior. The differences between measurement and simulation are discussed in the context of the limitations of simulation fidelity and measurement capability.
Article
The temperature can be determined either by observation of microstructural changes in the tool steel after cutting, or by measurement of changes in hardness using a microhardness test. In the range 650 degree -900 degree C the temperature at any position can be estimated with an accuracy of plus or minus 25 degree C. Details are given of the methods which have been developed. Temperature gradients in tools used to cut low-carbon iron and stainless steel illustrate the ability of these methods to determine temperature distribution in three dimensions through the tool under suitable conditions. The very steep temperature gradients emphasize the importance of knowledge of temperature distribution in dealing with problems of tool life.
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A review is presented of the current methods of assessing cutting temperatures occurring during turning operations. These methods are categorized as follows: thermo-e. m. f. (thermocouples) measurements; radiation measurements (infrared photography, pyrometry etc); and measurements based on thermochemical reactions (thermocolors). Methods of temperature calculation are also described.
Article
The aim of this work is to investigate the temperature distribution and heat generation when turning fully hardened AISI H13 hot work die steel (52 HRC) using De Beers DBC50 cutting tools over a range of operating parameters. Three different techniques were used: a) infrared radiation (using an optical pyrometer), b) implanted thermocouple and c) tool/chip thermocouple. Temperature was found to increase with cutting speed, feed rate, depth of cut and tool wear. Highest temperature values were observed when employing the tool/chip thermocouple, followed by the infrared pyrometer and the implanted thermocouple. However, an analysis of variance of the results indicated that the level of significance of each operating parameter to the recorded temperature varied according to the measuring technique.
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The grinding process requires a high input of energy which is virtually all converted to heat within the grinding zone. High temperatures are generated which may cause various types of thermal damage to the workpiece. The present paper presents an overview of quantitative methods to calculate grinding temperatures and predict thermal damage. For regular plunge grinding operations using conventional ceramic abrasive wheels, the grinding zone temperature is calculated using moving heat source theory coupled with a physical analysis to predict the fraction of the total grinding energy conducted as heat to the workpiece. This approach can be used to quantitatively predict the onset of workpiece burn at a critical grinding zone temperature, and also tempering and possible rehardening in the surface layer of hardened steels by coupling the temperature history with reaction rate models. For creepfeed grinding with slow workspeeds and large depths of cut, it is necessary to also consider the effect of cooling by grinding fluid `pumped' through the grinding zone by the porous wheel surface. Effective cooling at the grinding zone requires that the fluid temperature not exceed a critical burn-out limit for film boiling. An analysis is presented to predict the onset of burn-out by taking into account the ability of the porous rotating grinding wheel to pump fluid through the grinding zone together with heat transfer to the fluid, the workpiece, and the wheel. Finally, the effect of cubic boron nitride (CBN) superabrasive in place of conventional abrasive wheels is considered. CBN has a very high thermal conductivity which enhances heat transfer to the wheel, thereby reducing the grinding zone temperature and susceptibility to thermal damage.
Article
The effect of five design and three operating variables on three different drill temperature responses is investigated. A total of 512 observations was made using a replicated two-level factorial design. Problems associated with the selection of the temperature responses are studied including the transient nature of the response, the location of the thermocouple, and the interrelationship of the workpiece volume and drill wear. The five drill design variables are web thickness at point, margin width, relative lip height, helix angle, and surface condition, of which the helix angle and web thickness at point had the most significance within the experimental range. The effect of two-factor interactions was also discussed.
Article
This paper treats a fundamental investigation of tool wear and tool life mainly from the viewpoint of flank wear. The result reveals that the mechanism of tool wear in turning can be classified into two basic types: The mechanical abrasion which is directly proportional to the cutting distance and independent of the temperature; and the other is, so to speak, a physicochemical type which is considered to be a rate process closely associated with the temperature, of course. Although it depends upon the cutting condition which type of wear plays a more important role, the latter is predominant under usual conditions. According to the analyses and the experimental results, it has been found out that the tool life from the standpoint of flank wear can be predicted to a first approximation by the initial cutting temperature.
Article
This paper summarizes the results of theoretical and experimental studies of tool temperatures in interrupted cutting. In the theoretical study, the temperature in a semi-infinite rectangular corner heated by a time-varying heat flux with various spatial distributions is used to investigate the general nature of the tool temperature distribution. The results of this analysis are compared with infrared and tool-chip thermocouple cutting temperature measurements from interrupted end turning tests on 2024 aluminum and gray cast iron at speeds up to 18 m/s. The results show that temperatures are generally lower in interrupted cutting than in continuous cutting under the same conditions. Temperatures depend primarily on the length of cutting cycles and secondarily on the length of cooling intervals between cycles. For short cutting cycles the peak and average surface temperatures are relatively low, but they increase rapidly as the cutting cycle is lengthened and approach steady-state values for long cycles. Temperatures increase for very short cooling intervals, since in this case heat does not disperse between heating cycles, but for moderate and large values varying the cooling interval has little effect on temperatures. The theoretical analysis reproduces the qualitative trends but underestimates temperatures for short cutting cycles. The accuracy of the analysis could be improved by using a transient model to calculate the amount of heat entering the tool from the tool-chip contact.
Article
Through the energy method proposed in the previous parts of this study, it is possible to predict chip formation and cutting force for a single point tool of arbitrary geometry. By using the predicted results together with an assumption made on the stress distribution on the tool face, the temperature distribution within chip and tool is obtained through a numerical analysis. A characteristic equation of crater wear of carbide tool is derived theoretically and verified experimentally. Computer simulation of crater wear development is then carried out by using the characteristic equation, and the predicted distributions of the stress and the temperature.
A new three-color infrared radiation pyrometer using an optical fiber is developed for measuring cutting temperature in high speed machining by small ball end mill. The high speed air spindle unit is adopted to the ordinary milling machine so that the maximum spindle revolution of 40000rpm is attainable. The ball radius of the carbide cutter is 3mm and the side cutting of carbon steel with ballnose is executed without cutting fluid. Cutting temperature distribution along the ball-nosed cutting-edge is measured. The influences of spindle rotational speed, radial depth of cut and feed per tooth on the temperature distribution at the flank face are examined. The maximum temperature of peripheral cutting edge about 700°C is obtained even at the rotation angle of 180° after cutting, and it drops along the ballnose toward the ball tip. Relatively large temperature gradient arises along the ball cutting-edge at higher spindle revolution because cutting speed depends on the local tool radius. Depth of cut and feed per tooth, at the same time, affect the overall temperature at the ball cutting edges. The cooling characteristics in air cutting reveals that the temperature difference during one cycle of intermittent cutting increases as spindle speed decreases. The relationship between the peripheral cutting speed and the tool temperature varies from tool shank to ball tip because the interactions between cutting edge and workpiece change along the ballnose.
Article
A sandwiched thermocouple technique was developed to measure the grinding temperature. This technique has the advantage over the wheel-work thermocouple method developed previously as individual calibrations are not required when different workpieces are used. In order to account for the thermal inertia effect of the thermocouple junction, a constant heat source was designed to simulate the action of the grinding wheel whereby the thermal inertia characteristics of the thermocouple can be established. Experimental values of the grinding temperature are compared to the theoretical values derived from considering the specific grinding energy. Discrepancies of the findings and the validity of the technique are also discussed.
Article
An analytical temperature distribution along the cutting edge and on the flank face of a drill is obtained using Tsueda’s and Loewen and Shaw’s equations after modifications. Experimental temperature distributions are also investigated and the effects of a pilot hole and the heat sink are evaluated. Agreement between the analytical and experimental results is fairly close except near the chisel edge and near the drill periphery. The use of workpieces containing a pilot hole provides a method to account for the discrepancy between the analytical solution and the experimental results near the chisel edge while some explanation is offered to describe the discrepancy near the drill periphery.
Article
The measurement of temperature distribution at the flank surface of a cutting tool is characterized by the extremely small extent of the surface over which the temperature field is explored. This paper describes a technique which makes use of a moving lead-sulfide, photoconductive, infrared radiation detector. The surface in question is quickly scanned by the detector’s view field. For the level of temperature encountered, data are reproducible and the method may be used to determine temperature distribution over sliding contacts in general. From the measured flank surface temperatures, tool-chip interface temperature distribution was deduced using geometrical, electric analog. The technique also has the general application in finding steady temperatures at locations which are not accessible for direct measurement. The computed tool-chip-interface temperature profile agrees well with known crater-wear patterns. Tool-face frictional force calculated from thermal considerations compares favorably with independent dynamometer measurement.
Article
The temperature of cutting grains on wheel surface was measured by means of a new method, in which an optical fiber accepts the infrared flux radiated from the cutting grains and transmits it to an infrared detector InAs cell. This pyrometer makes it possible to observe the history of each cutting grain on the wheel surface. It was found that the temperature of cutting grains at 4. 2 ms after cutting is distributed in the range of 500 degree C to 1400 degree C, and their mean temperature is 820 degree C.
Article
The temperature of interface between a cutting tool and a chip in dry and wet turning is measured using two color pyrometer with a fused fiber coupler. A translucent Alumina sintered under HIP (Hot Isostatic Pressing) is used as the cutting tool, and 0.45% carbon steel (S45C) is used as a workpiece. The water soluble fluid (Sunlight TC-800) is used as the cutting fluid, and is introduced onto the rake surface of the tool with a nozzle (diameter: 5 mm). The infrared rays radiated and transmitted through the translucent tool are accepted by an optical fiber, and separated to two optical fibers at fused fiber coupler. Each fiber leads the infrared ray, respectively, to two infrared detectors of different spectral sensitivity. Temperature is obtained by calculating the ratio of the output voltage from these two detectorS. The result obtained are as follows: (1) The technique developed is suitable for measuring the interface temperature between a cutting tool and a chip. (2) The interface temperature is highly affected by the cutting speed, and the temperature increases very rapidly with the increase of cutting speed. (3) The interface temperature reduced 30°C in the wet cutting. Finally, the temperature distributions on the cutting tool and the work material are analyzed by using a finite element method (FEM). Good agreement is obtained between the analytical results and the experimental ones.
Article
This paper deals with an experimental and analytical investigation into the different factors which influence the temperature distribution on Al2O3TiC ceramic tool rake face during machining of difficult-to-cut materials, such as case hardened AISI 1552 steel (60–65 Rc) and nickel-based superalloys (e.g. Inconel 718). The temperature distribution was predicted first using the finite element analysis. Temperature measurements on the tool rake face using a thermocouple based technique were performed and the results were verified using the finite element analysis. Experiments were then performed to study the effect of cutting parameters, different tool geometries, tool conditions, and workpiece materials on the cutting edge temperatures. Results presented in this paper indicate that for turning case hardened steel, increasing the cutting speed, feted, and depth of cut will increase the cutting edge temperature. On the other hand, increasing the tool nose radius, and angle of approach reduces the cutting edge temperature, while increasing the width of the tool chamfer will slightly increase the cutting ege temperature. As for the negative rake angle, it was found that there is an optimum value of rake angle where the cutting edge temperature was minimum. For the Inconel 718 material, it was found that the cutting edge temperature reached a minimum at a speed of 510 m/min, and feed of 1.25 mm/rev. However, the effect of the depth of cut and tool nose radius was almost the same as that determined in the turning of case hardened steel. It was also observed in turning Inconel 718 with ceramic tools that, cutting forces and different types of tool wear were reduced with increasing the feed.
Article
An experimental study is performed using both thermocouples and infrared thermovision to monitor timewise temperature variations of the tool and workpiece in orthogonal cutting. A semi-empirical formula is derived to express the temperature-time history of the tool surface, using a local element lumped conduction equation with experimental data-fitting. Infrared thermovision identifies the location of the maximum tool temperature slightly inward from the cutting edge. An optical and electronic microscope reveals the formation of micropits, the origin of flank and rake wear that originates in the region of surrounding the maximum tool temperature. It is disclosed that the progression of wears is accompanied by a consistent increase in the tool temperature which in turn accelerates the wearing process. Chip geometry is found to affect local steady-state temperatures in the cutting tool. For cast iron and copper, chip geometry may causes a zig-zag variation in the steady-state temperature with respect to the rate of material removal for a change in the feed. The study sheds light on the causes of roughness of surfaces cut with a hard tool and may thus serve as the first step in the investigation of surface machining.
Article
The present paper deals with the high-speed machining of Inconel 718 and Ti6Al6V2Sn alloys from a thermal point of view. Temperature and wear of cutting tools are investigated by means of cutting experiments and numerical analysis up to a cutting speed of around 600 m min−1. For Inconel 718, severe wear of ceramic tools, particularly highly developed boundary notch wear, is correlated with variation of the chip formation mechanism from continuous,to discontinuous, which is accompanied by large side flow of the chip and plastic burrs of the workpiece. This indicates that the wear is developed by an abrasive process rather than by a thermally activated mechanism. A TlC-added alumina tool is superior to silicon nitride across a speed range from 250 to 500 m min−1, where the cutting temperature exceeds 1200°C. In end milling of the titanium alloy, high-speed machining up to a cutting speed of 628 m min−1 (20 000 r.p.m.) is possible for sintered carbide tools. Measurements of cutting temperature during intermittent turning of a titanium disk, which is modelled on milling, reveal that the feasibility of high-speed end milling depends on a transient temperature rise or ‘time-lag’, owing to a short cut distance of the tool edge per single revolution, the existence of the helix angle, and a temperature drop through the use of a coolant. These factors contribute to the reduction of tool temperature. Finally, a numerical model is proposed to validate the temperature measurement.
Article
The problem of dependent cut joint constraints for kinematic loops in rigid multibody systems is addressed. The constraints are. reduced taking into account the subalgebra generated by the screw system of the kinematic loop. The elimination of dependent constraint equations is based on constructing a basis matrix of the screw algebra generated by loops screw system. This matrix is configuration independent and thus always valid. The determination of the sufficient constraints is achieved with a SVD or QR decomposition of this matrix. Unlike all other proposed approaches the presented method is singularity consistent because it is not the Jacobian which is decomposed, but instead a basis matrix for the loop algebra. Since this basis is obtained after a finite number of cross products the computational effort is negligible. Furthermore, because the elimination process is only necessary once in advance of the integration/simulation process, it proved valuable even if it does not remove all dependent constraints, as for paradoxical mechanisms.
Article
This paper addresses modeling of the tool temperature distribution in self-propelled rotary tool (SPRT) machining of hardened steels. Since tool life is significantly influenced by cutting temperatures, a model is developed to analyze the heat transfer and temperature distribution in rotary tool turning of hardened 52100 steel (58 HRC). The model is based on the moving heat source theory of conduction and employs the finite element method (FEM) for its solution. The model is experimentally verified through measurements of the cutting tool temperature distribution using an infrared camera under different cutting conditions. Finally, both rotary and equivalent fixed tool cutting processes are compared in terms of cutting tool temperatures generated.
Article
Experiments on the infrared radiation in surface grinding were conducted using both highly sensitive infrared films and photocells covering most of the interesting spectral range. The “Thermovision” technique applied in tests was coupled with the videotape recording equipment providing a dynamic picture of the events. It was revealed that the stream of hot chips propelled by the grinding wheel that impinge on the workpiece surface represents an additional thermal input; this can be prevented by directing the coolant at the point where the chips leave the grinding zone. The studies suggest that the surface of a grinding wheel is not cooled completely during the non cutting portion of a revolution. They indicate also that the variation in sharpness and wear of the abrasive particle causes changes in the energy significant enough to influence the level of infrared radiation. The effect of thermal deformation on thermal emission in reciprocating surface grinding points out the importance of efficient cooling of the workpiece during the operation in order to maintain the dimensional accuracy. Analysis of experimental results indicates that infrared radiation from wheel and workpiece surfaces provides valuable insight into the grinding process.
Article
Theoretical and experimental analyses of orthogonal micromachining of copper are, presented to promote fundamental understanding of ultraprecision metal cutting process. A method is proposed by applying the rigid-plastic FEM to analyze the mechanics of steady state orthogonal micromachining process of copper taking into consideration of the roundness of the tool edge. An FEM model is also developed to analyze the flow of cutting heat and the temperature distribution within both the workpiece and the tool based on the stress and the material flow within the workpiece calculated. Orthogonal micromachining experiments are carried out by employing both a micromachining equipment installed within SEM (Scanning Electron Microscope) and an ultraprecision fly cutting machine. The results of the FEM analysis are compared with the experimental results.