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Fundamental knowledge of frictional phenomena in cutting processes is elemental for their further development. Both pin-on-disc and open tribometer are able to replicate the sliding velocities and contact pressures during cutting to some extent; however, open tribometer can simulate continuous sliding against freshly regenerated surface. In this pa...
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... principle of open tribometer is shown in Figure 1 in isometric and top view. The cutting insert (2) is sliding against the rotating workpiece (1) creating an elliptical contact area. ...
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... Figure 10 apparent contact area on cutting insert for dry conditions (30 m/min) on open tribometer is shown. ...
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... comparison of obtained friction coefficient on both tribometers in dry conditions is showed in Figure 11. While the friction coefficient remained constant on open tribometer, distinctive running-in phase was observed on pin-on-disc. ...
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... the average friction coefficient is shown for two sliding distance intervals -between 0 and 20 meters (runningin) and from 20 to 80 meters where the friction coefficient stabilized. In Figure 12, measured friction coefficients are showed for lubricated conditions (5% emulsion). Friction coefficient is comparable between the two tribometers. ...
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... obtained friction coefficients are comparable to dry conditions. This is also observed in the case of lubricated conditions with Castrol MQL oil, shown in Figure 13. In the lubricated conditions with the Castrol MQL oil the friction coefficient is marginally lower (~10%) compared to dry conditions. ...
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... to strong chemical adhesion we assume that the adhesive forces are predominant reason for the inability of used lubricants to reduce the friction coefficient. In the case of cryogenic conditions (LCO2) the measured friction coefficient does not differentiate much from dry conditions, as seen from the Figure 14. Similar results were observed in the study by Meier et al. [23], which used coated tungsten carbide and Ti6Al4V on three types of tribometers in dry and lubricated conditions. ...
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Citations
... These differences include point versus area contact, various types of material pairs (hard ball and soft/ductile chip), strong adhesion of the material during the chip formation process, different temperatures, pressures, and relative velocities in the contact zone between both sliding elements, different lubrication conditions, and various wear intensities of the structure during sliding. A limited correlation with cutting was observed, as reported in [24], despite the common use of specific open tribometers [25] and the application of pin tribometers under cryocooling conditions [26]. In recently published studies, Lian et al. [27] demonstrated this approach for the circular motion of a titanium ball on a structured surface. ...
This study evaluated the feasibility of laser-textured biomimetic designs for cutting tools to investigate the effects of laser-textured tools combined with cryogenic cooling using liquid nitrogen (LN 2) on the tool-chip interface, built-up edge (BUE) formation, and friction during Al-MMC machining. This study involved selecting a bio-mimetic design, converting it into a textured cutting tool, evaluating the coefficient of friction (CoF) and cutting forces on the textured surface under dry conditions, and using cryogenic LN 2 as a coolant with the textured tool. Femtosecond lasers were used to precisely create biomimetic surfaces near the rake face edge without compromising tool integrity. The pin-on-disc method revealed no significant CoF difference between plain and textured tools or among textured tools within the determinate pin load impact. Dry machining tests showed a higher CoF than the pin-on-disc method owing to strong workpiece material adhesion. Cutting force analysis under dry and textured conditions showed negligible effects on aggregate force components, although textured tools had a higher feed force than untextured ones. Cryogenic cooling with plain tools reduced BUE height, TCC length , and TCCarea compared to dry conditions. Textured tools in dry conditions increased BUE height and acted as chip breakers, reducing TCC length and TCCarea compared to dry plain tools. Most textured tools with cryogenic cooling reduced the BUE height, TCC length , and TCC area compared to their dry-textured counterparts. The findings suggest that combining biomimetic textured cutting tools with cryogenic machining is a promising approach for sustainable manufacturing of Al-MMC's.
... To solve this problem, scholars have developed the open ball-disc tribo-system to achieve the single sliding of a ball on the fresh surface of the workpiece [16][17][18][19]. Bonnet et al. [20] developed a new friction model to calculate the friction coefficient between 316L stainless steel and TiN-coated carbide during the dry sliding process. ...
Ultra-high-strength steels have been considered an essential material for aviation components owing to their excellent mechanical properties and superior fatigue resistance. When machining these steels, severe tool wear frequently results in poor surface quality and low machining efficiency, which is intimately linked to the friction behavior at the tool–workpiece interface. To enhance the service life of tools, the adoption of efficient cooling methods is paramount. However, the understanding of friction behavior at the tool–workpiece interface under varying cooling conditions remains limited. In this work, both air atomization of cutting fluid (AACF) and ultrasonic atomization of cutting fluid (UACF) were employed, and their spray characteristic parameters, including droplet size distribution, droplet number density, and droplet velocity, were evaluated under different air pressures. Discontinuous sliding tests were conducted on the ultra-high-strength steel against cemented carbide and the effect of spray characteristic parameters on the adhesion friction coefficient was studied. The results reveal that ultrasonic atomization significantly improved the uniformity of droplet size distribution. An increase in air pressure resulted in an increase in both droplet number density and droplet velocity under both AACF and UACF conditions. Furthermore, the thickness of the liquid film was strongly dependent on the spray characteristic parameters. Additionally, UACF exhibited a reduction of 4.7% to 9.8% in adhesion friction coefficient compared to AACF. UACF provided the appropriate combination of spray characteristic parameters, causing an increased thickness of the liquid film, which subsequently exerted a positive impact on reducing the adhesion friction coefficient.
... The EDS analysis are consistent with the results of [16], which reported that the cryogenic bath limited efficiently the occurrence of adhesion. Similarly, the authors of the study [18] indicated that the introduction of lubrication fluid or Minimum Quantity Lubrication (MQL) reduced the contact area by 35 % compared to dry friction. These studies confirm that the choice of lubrication configuration restricts the phenomenon of adhesion compared to dry friction. ...
During machining, the friction between the tool and the workpiece (cutting face and flank face) is a significant tribological phenomenon because it strongly influences the cutting operation. Indeed, higher friction leads to an increase of cutting forces, a greater heat generation, a premature tool wear and a surface degradation. This study focuses on tool (WC/Co)/workpiece (Ti-6Al-4V) friction under different cooling conditions (dry, emulsion, cryogenic). Determining the friction coefficient requires numerical simulations to separate the tribological phenomena. For this purpose, several modeling methods are compared (Lagrangian, CEL, and ALE). Experimental tests revealed that the friction coefficient depends not only on the sliding velocity but also on lubrication modes. Specifically, the lowest friction coefficient is obtained under cryogenic condition. Adhesive phenomena on the WC/Co pin are observed in the friction zone, particularly at high sliding velocities.
... This does not correspond to the processes in the chip formation zone, which is an open tribological system [3]. Sterle et al. could prove within a comparative study that an open tribometer results in significantly higher coefficients of friction than a closed one [6]. In order to bring the tribometer closer to the conditions in the chip formation zone, a few different open tribometer have been developed. ...
In machining, tool temperatures and thus tool wear are significantly influenced by frictional behaviour. Friction tests are used to determine the friction coefficient depending on relative speed, which serves as basis for parameterising friction models as input data for chip formation simulations. Therefore, this paper represents investigations towards the frictional behaviour of uncoated and coated (TiN, TiAlN) carbide tools when using two different relative movements (translational and rotary) and cooling lubricant conditions. In dry conditions, the investigations show insignificant influence of different engagement surfaces and testing kinematics on resulting friction. In lubricated conditions, three different friction coefficient sections were observed.
... Another study, conducted by Luka et al. [46], validated the proposed percentage of friction coefficient reduction. They utilised an open tribotester to evaluate the frictional behaviour of identical workpiece and cutting tool materials as those used in this study. ...
Predicting the tribological behaviour in the secondary shear zone in the metal-cutting processes is considered a significant challenge in contemporary research. This work investigated the frictional performance in the secondary shear zone of a planing process using a modified ball-on-disc open tribometer. The values of the coefficient of friction (COF) were tracked between an AISI4140 + QT disc (chip) and a cemented carbide ball (cutting tool) coated with TiAlN under three contact pressures of 0.5, 1, and 2 GPa at a range of sliding speeds starting from 0.2 m/s to 1.6 m/s. The tests were conducted under both dry and lubricated conditions using three commercial cutting fluids of CSF 35 straight oil, Vasco 6000, and Zubora 67H emulsions. Also, the MWFs were tested for their rheological properties and wettability. The tribometer results validated the same COF trend as that in the actual metal-cutting experiments, particularly at 0.5 and 1 GPa in dry conditions. Moreover, Zubora 67H emulsion is proven to be the optimal choice due to it reducing the COF between the rubbing contacts by up to 78%. Furthermore, it showed the lowest contact angle and viscosity index, revealing its ability to easily penetrate, especially at higher temperatures, within the secondary cutting zone.
... Therefore the analysis of influencing factors and the optimization of processes is of great importance [5]. During the machining process, thermo-mechanical loads and friction directly impact tool life, the quality of the machined products and productivity [6]. Over 90% of all carbide tools are coated [7], with physical vapor deposition (PVD) method accounting for the vast majority. ...
... To extract the cutting force and temperature values more accurately during the cutting process, the mesh elements of the tool and workpiece are coupled with a four-node plane strain element with temperature-displacement. The friction coefficient between the tool and workpiece in the finite element model is selected as 0.2 [30]. ...
Titanium alloys are extensively utilized in the aerospace industry due to their exceptional properties, encompassing high specific strength and corrosion resistance. Nevertheless, these alloys present inherent challenges as difficult-to-machine materials characterized by low thermal conductivity and high chemical reactivity. The machining of titanium alloys often gives rise to elevated cutting forces and temperatures, thereby resulting in compromised machining quality and substantial tool wear. This study explores the influence of the cutting-edge shape factor on tool performance and optimizes the cutting-edge structure through finite element simulation. Remarkably, the cutting performance of the tool demonstrates significant enhancement following cutting-edge passivation. Alterations in the geometric shape of the cutting-edge after passivation exert a notable impact on the tool’s cutting performance, with a superior performance observed for shape factor K > 1 compared to alternative edge structures. Additionally, numerical simulation is employed to analyze the influence of passivation values Sγ and Sα on cutting force and temperature, which are crucial factors affecting cutting performance. The results underscore the significant impact of Sγ on cutting force and temperature. Furthermore, within the confines of maintaining an identical shape factor K, the blade segment group featuring Sγ = 40 μm and Sα = 25 μm exhibits the lowest maximum cutting temperature, thereby indicating the optimal tool design attainable through this study.
... Wear is acknowledged to be caused by defective design, insufficient lubrication, inappropriate lubrication, terrible craftsmanship, rough finish on surface, insufficient clearance between surfaces, competition with dust/metal particles, effect of most air, water, and chemicals, effect of temperature, and improper tooling, with friction playing a key role. Reducing the coefficient of friction in machining operations offers numerous benefits, but it necessitates a change in tool design (Luka et al., 2019). Hard coatings are subjected to shear, tensile, and compressive stresses, which can cause cracking and spalling failure, according to Abadias et al. (2018). ...
Wear phenomenon impact the operating efficiency and service life of engineering materials due to the influence of surface interaction at different working conditions. Successive tribological studies on wear-resistant materials in the last decade is estimated at approximately 40% of friction and wear, including laboratory tests. Most locally improvised wear testers in accordance with American Society for Testing and Materials (ASTM) and European (EN) standards, though, achieve 95–97% parametric accuracies with reduced cost, they hardly harmonize degradation and Archards coefficients for all possible wear factors, providing little data for simulation of mechanical and chemical wears which are responsible for non-uniform aggregation of wear patterns in practice. Complexities of intermeshing factors which combine to influence the effectiveness of developed test devices span over loads, speeds, temperatures, pressures, and ambience for various applications. This study highlights the techniques of wear characterization, test standards, and wear reduction with emphasis on surface texturing for improved eta/beta phase re-arrangements at low working temperatures in the enhancement of grain contraction during high bias-voltage cathodic substrate multi-phase coating, phosphating during pretreatments using peening techniques, residual stress reduction during cryogenic heat treatments as well as the impact of suitable architectural matrix composite strengthening, microstructures, and material reinforcements as suitable factors to influence improved tribological behaviors in materials. Optimal additive manufacturing (AM‐fabricating) techniques with pretreatments, thermal cycling, and tempering can engineer enhanced anti-tribocorrosion in automotive components.
... When using cryogenic media, improvements with regard to the lubricating effect were also observed [26,27]. In the case of LN 2 , for example, the lubrication could be explained by boundary layers that are formed as a result of cushion effects of the rapid vaporizing LN 2 [26]. ...
... In the case of LN 2 , for example, the lubrication could be explained by boundary layers that are formed as a result of cushion effects of the rapid vaporizing LN 2 [26]. Sterle et al. attributed the slight improvement in the lubricating effect when using cryogenic media to a condensation of the atmospheric moisture on the tool, workpiece and chip due to a cooling of these solids below the dew point [27]. However, in other tribological studies, it has been observed that the lubricating effect of cryogenic media causes COFs that mostly differ only slightly from those obtained by dry condition [28,29]. ...
... Open and closed tribological systems differ not only in terms of the kinematic, but also regarding the contact conditions, in particular the apparent COF (μ app ): According to Bowden and Tabor, a simplified approach can be used to separate the apparent COF μ app into a COF for plastic deformation (μ plastic ) and a COF for the adhesive phenomena between the friction partners (μ adhesion ) [54]. Closed tribological systems are characterized by run-in-events in which the plastic deformation portion decreases with time and approaches μ adhesion [27]. ...
This paper aims at an improved understanding of the influence of different cooling and lubrication conditions on the tribological behavior at extremely high contact pressures. A novel tribometer was used to investigate the tribological behavior of the material pairing AISI 4140 Q + T and WC-Co carbides, which is common in cutting processes. Regarding the cooling and lubrication conditions, dry condition, liquid nitrogen (LN2), carbon dioxide snow (CO2), and two different types of sub-zero metalworking fluids (sub-zero MWF) were investigated. The tribological behavior is analyzed on the basis of the thermo-mechanical load in the tribological contact, the coefficient of friction, and the surface topography of the friction partners. Furthermore, the influence of the hydrodynamic lubrication gap height, resulting from different types of sub-zero metalworking fluids, on the lubricating effect is investigated. The analysis shows that the use of cryogenic media resulted in a substantial reduction of the thermal load. However, the coefficients of friction as well as the topography of the friction partners indicate that a lubricating effect can only be achieved up to a contact pressure of roughly 2100 MPa. In contrast, both types of sub-zero MWFs led to a high lubricating effect even at contact pressures of up to 3600 MPa. By using both types of sub-zero MWFs at a supply temperature of -30 °C a high cooling effect was also achieved. A higher hydrodynamic lubrication gap height can be beneficial for the lubricating effect depending on the type of sub-zero MWF. In this context, however, further friction-reducing effects such as adsorption films need to be considered.
... Sterle et al. [4] developed a tribometer based on a lathe in which a cutting insert is pressed against a rotating workpiece and slides following a helical path, while the normal and tangential forces are measured with a piezoelectric dynamometer. The results for a low alloy steel were compared with those obtained using a commercial pin on disc tribometer under similar conditions and showed equivalent results for dry tests. ...
This work presents an experimental-numerical approach aimed at determining the chip-tool contact length during orthogonal cutting of annealed AISI 4340 steel (223 HV) with TiN coated tungsten carbide inserts. Initially, pin on disc tests were performed, followed by orthogonal cutting tests. The components of the cutting force were used to calculate the coefficient of friction in orthogonal cutting and its value was compared with those obtained under sliding. Moreover, the cutting force components obtained experimentally were used to assess the reliability of the finite element model, used to estimate the temperature in cutting zone. The contact length between chip and rake face was calculated based on the experimental feed force and shear strength of the work material and was compared with the results provided by an analytical model. The experimental-numerical approach can be considered more accurate due to the fact that it considers the effect of the tool-chip interface temperature on the shear strength of the work material. However, the analytical model is quite straightforward, since it only requires the values of chip thickness and undeformed chip thickness to estimate the tool-chip contact length.
