Tool Rake Face Research Articles

Cutting force prediction model considering tool-chip contact interface friction behavior in ULTVAM of Ti-6Al-4V

Ti-6Al-4V is widely used in the aviation industry because of its high strength, and good heat resistance. However, severe tool wear on the rake face occurs during the milling of Ti-6Al-4V, which is caused by intense friction between the tool rake face and the chips. To investigate tool wear in the milling of Ti-6Al-4V, ultrasonic vibration is introduced, and a cutting force prediction model that considers tool-chip contact interface friction behavior in Ultrasonic Longitudinal-Torsional Vibration-Assisted Milling (ULTVAM) is proposed in this paper. First, the tool tip motion trajectory and dynamic cutting thickness under ULTVAM were analyzed calculated, and compared with those in Common Milling (CM). Subsequently, the effects of ultrasonic vibration on the shear force under the ultrasonic softening effect, the friction force, and the friction reversal force on the tool-chip contact interface were investigated. A dynamic milling force model under ULTVAM was established before and after friction force reversal caused by ultrasonic longitudinal-torsional vibration. Finally, numerous experiments were conducted to validate the proposed model, and the experimental results indicated that the calculated dynamic milling forces agreed well with the measured values, with errors in the X and Y directions of 5.51% and 10.23%, respectively. In addition, the average roughness of the workpiece surface also decreased (1.08, 0.9, 0.6, 0.7 μm under ultrasonic amplitudes of 0, 1, 2, and 3 μm) and the tool wear state improved on the rake face under ULTVAM.

Effects of longitudinal ultrasonic vibration on tool wear behaviors in side milling of GH4169D superalloy

The GH4169D superalloy, a novel Nickel-based material widely acknowledged for its exceptional high temperature strength and fatigue resistance properties, plays a pivotal role in the production of critical components of contemporary aero-engines. The material, however, falls under the category of a typical difficult-to-cut metallic material due to the substantial cutting forces and significant tool wear experienced during the machining process. In this paper, a method of longitudinal ultrasonic vibration assisted side milling (LUVM) was developed to extend tool life. The investigation primarily involved an analysis of tool wear behaviors, including milling force, tool life, morphologies of tool wear, and various underlying wear mechanisms in LUVM and conventional milling (CM) of GH4169D superalloy. The results demonstrate that LUVM exhibits the advantage of reducing milling forces and prolonging tool life in comparison to CM. Throughout the entire milling process, the maximum milling force of LUVM is consistently smaller than that of CM, displaying a comparatively slower growth trend. At the conclusion of machining, while CM reaches a maximum milling force of 360.3 N, the maximum milling force of LUVM (195.9 N) is significantly lower. The tool life of LUVM is 28.2 min, representing a 33 % increase compared to CM (21.2 min). Material adhesion, coating delamination, and built-up edge (BUE) phenomena can be observed on both the tool rake face and flank face in CM. LUVM contributes to mitigation of bonding phenomena, prevention of BUE formation, and avoidance of abrasive wear in comparison to CM. However, it is prone to lead to tool tip chipping. For CM, the tool wear mechanisms include adhesive wear, oxidation wear, abrasive wear and diffusion wear; whereas for LUVM, the tool wear mechanisms comprise of adhesive wear, oxidation wear and diffusion wear.

Development of Machining Device with Real-Time Visualization of Boundary Surface on Tool Rake Face and Cutting Chip

Analysis of cutting phenomena has been conducted for a long time and many researchers have elucidated the phenomena that may occur at the cutting-edge during machining; for example, built-up edges and welding phenomena on cutting edge. However, the existing research has focused on observing the tool and chips after machining, when the tool and work material have been cooled, and are under atmospheric pressure. Therefore, we consider that it is different from the phenomenon that occurs during cutting. Because the cutting edge of a tool is in a high-temperature and high-pressure environment during machining and is released from such an environment after machining, the cutting edge must be visualized to discuss the actual cutting phenomena. There have been research reports in the past that have visualized the backside of cutting chips; however, that experiment was far from actual cutting phenomena and was conducted at significantly low cutting speed. Thus, the visualization of the cutting phenomenon is physically extremely difficult at the cutting edge. Under such circumstances, this study developed a device that observed the behavior of the boundary surface between cutting chips and the rake face in real time from the backside of the rake face during machining. By using the developed device, we could visualize this phenomenon to acquire the data directly and visually, which can otherwise be grasped only indirectly. In this device, a camera was mounted on a tool holder, and a cutting tip made of a transparent material was used to observe rake face, cutting edge, and flank face which can be visualized during machining from the backside of the rake face within one field of view. This paper reports on the outline of the developed device, its method, and the results of experimental observation of the state of two-dimensional cutting using a lathe.

Diamond machining of additively manufactured Ti6Al4V ELI: Newer mode of material removal challenging the current simulation tools

Single point diamond machining (SPDM) produces smooth machined surfaces that other production methods cannot match. While the mechanics of machining of cast alloys with SPDM is well-explored, the realm of SPDM for additively manufactured parts remains largely uncharted. This work reveals new insights into the surface generation process of an additively manufactured titanium alloy, specifically, a Ti6Al4V Extra Low Interstitials (ELI) alloy workpiece. Our examination of the chip morphology unveiled a distinct mode of chip removal, previously unrecorded in existing literature. During SPDM of additively made Ti6Al4V ELI workpiece, identification of numerous pores and discontinuities in the chips flowing on the tool rake face, indicating periodic intermittent cracking during the material's plastic flow was seen. To examine this phenomenon, a finite element analysis (FEA) model was developed. While the FEA model can well explain the machining mechanics and chip morphology of SPDM of cast Ti6Al4V ELI reported in the literature, it failed to describe the chip morphology that are obtained during machining of additively made workpiece in this work. This disparity underscores the need for innovative simulation approaches tailored for additively manufactured components. The experimental observations in this study highlight a unique form of chip formation in contrast to conventional Ti6Al4V alloy machining processes. At lower feeds, there was a presence of short, discontinuous chip formation with tearing at the outer periphery. Conversely, at higher feeds, a long, continuous ribbon-like chip formation was observed. In addition, some typical additive manufacturing defects appear on the machined surface and chips. Through optimisation of the SPDT parameters, a surface roughness (Ra) value of about 11.8 nm was achieved on additively manufactured Ti6Al4V ELI workpiece. This work provides a fresh perspective on the mechanics of SPDM for additively manufactured components, offering a stepping stone for subsequent studies.

Analytical model of modified diamond tools temperature by focused ion beam in dry diamond turning

The contact process between the chip and the rake face is directly affected by the temperature of the rake face, and then tool wear and machining quality is indirectly influenced by it. In this study, a temperature prediction model for the rake face of modified diamond tools during dry turning of the 6061 aluminum alloy was established based on the moving heat source method. The shear heat source, rake face chip friction heat source, cutting edge-workpiece ploughing effect heat source, cutting edge workpiece roll burnishing heat source, and flank face workpiece elastic recovery heat source were considered by this model during the dry diamond turning, simultaneously considering the non-uniformity of heat source intensity and heat distribution ratio, as well as the influence of ion implantation on the temperature of the tool rake face. The experimental results indicate that this model successfully predicts the temperature of the modified tool rake face, and it is found that an increase in dose will promote a decrease in the temperature of the rake face. Theoretical analysis reveals that modified cutting tools have the characteristic of reducing the temperature of the rake face, revealing the essence of the influence of “modification” on the temperature of the rake face from the perspective of the cutting mechanism, and providing a theoretical basis for optimizing modification parameters.

Finite Element Simulation of Orthogonal Cutting of H13-Hardened Steel to Evaluate the Influence of Coatings on Cutting Temperature

High cutting temperatures increase tool wear and reduce tool life. To achieve a longer tool life, coated carbide tools have been developed. In this study, the influence of tool coatings on the cutting temperature distribution during the orthogonal cutting of H13-hardened steel is investigated. Firstly, four coating materials, including TiC, TiN, Al2O3, and TiAlN, with the same coating thickness, are selected to evaluate the effects of coating materials on cutting temperature with finite element simulation. The maximum temperatures at the tool rake face and the temperatures at the coating–substrate interface are evaluated. It was found that the maximum temperatures at the tool rake face were the lowest and the highest when TiN and Al2O3 coating materials were applied, respectively. The TiAlN coating material had the best thermal barrier property. Then, the temperature distribution along the direction perpendicular to the tool rake face is investigated for TiAlN-coated tools with different coating thicknesses ranging from 3 μm to 10 μm. It is shown that the temperature gradient increases with the coating thickness. The coating thickness should be kept below 5 μm. Finally, cutting experiments validate the availability of the finite element model.

Development of a numerical cutting model for understanding the chip formation in cryogenic machining

The aim of this study is to develop a finite element model of metal cutting that includes fluid structure interaction. The proposed model is used to improve the physical comprehension of the chip formation during cryogenic assisted machining. This is performed based on the coupled-Eulerian-Lagrangian formulation. An algorithm is also developed to ensure heat exchange between the fluid and the structure. It also allows decoupling the mechanical and thermal effects induced by liquid nitrogen. The titanium alloy Ti17 is used as a work material, and uncoated tungsten carbide is used as a tool under dry and cryogenic conditions with cutting speeds of 50 m/min and 70 m/min and feeds of 0.1 mm/rev and 0.2 mm/rev. Simulation is validated by comparison with the experimental results. Standard deviations of both forces and chip thickness are low; they stay under 15% and 35% of the average value, respectively. The chip formation, the cutting force and the temperature are studied. It is shown that cryogenic machining has a significant effect on the chip formation and the temperature distribution in the cutting zone. A remarkable temperature reduction by up to 500 °C is observed at the tool rake face. However, the tool tip temperature slightly decreases with the application of liquid nitrogen when compared to dry machining.

Performance of Liquid Nitrogen (LN2) on Machining Pure Titanium (Grade 2): A Comparative Study

The biggest challenge for manufacturing industries is machining super alloys due to their properties. Titanium grade 2 also comes under the category of difficult cut material. In this present investigation, the green manufacturing technology was applied to cut the titanium grade 2. The comparison study was carried out between dry and cryogenic machining. The turning trails were performed using TiN-coated carbide cutting tools. Cutting force measurements surface roughness as well as the tool wear studies were carried out with the Kistler dynamometer, SURFCOM and SEM analysis. From the responses, under cryogenic cooling 32.5% of main cutting force reduction was observed when contrasted to dry condition at a cutting speed of 282 m/min. The 24 % of improved surface quality was observed under cryogenic cooling approach, more fracture on tool rake face was observed under dry condition and the favorable chip formations were also noted under cryogenic cooling approach.

Precision tailoring of laser beam propagation in a single crystalline diamond tool for in situ laser-assisted diamond turning.

The characteristics of laser beam propagation within a diamond tool critically influence the applied thermal softening capability of in situ laser-assisted diamond turning (In-LAT). In the present work, we perform optical geometric analysis, optical simulation and experimental validation to propose a novel diamond tool configuration for precisely tailoring laser beam propagation in In-LAT. First, the characteristics of laser beam propagation in the current In-LAT diamond tool are theoretically and experimentally explored. Second, according to the issues discovered in the current In-LAT diamond tool, an improved tool configuration based on the total internal reflection of a laser beam within the diamond tool is proposed, aiming for promoting refraction of the laser beam from the rake face of the diamond tool as well as eliminating the reflection of laser beam to tool holder. Finally, the optimization of laser beam incident position is carried out for achieving the superior profile and intensity of the emitted laser spot. Current work provides rational laser beam propagation for improving the thermal-softening capability of an In-LAT diamond tool.

Experimental study on the effect of CNT-enriched nanofluid lubrication on the performance of textured cutting tool in the turning of aluminum 7075 alloy

This paper investigates the impact of surface texturing and the use of CNT-enriched nanofluid lubrication on the cutting performance of cemented carbide cutting tools during the turning process of aluminum 7075 alloy. Aluminum 7075 is widely utilized in various industries due to its exceptional properties, including high corrosion resistance, a favorable strength-to-weight ratio, and good formability. However, this alloy tends to excessively adhere to the cutting tool at the tool-chip interface, which negatively affects the machining process. Previous research has proposed different solutions, but the current study focuses on implementing the two most effective approaches to minimize adhesion phenomena. The first approach involves modifying the contact area by creating a pattern on the tool's rake face, while the second approach utilizes CNT-enriched nanofluid lubrication to reduce friction in the tool-chip interface. Various types of surface textures were fabricated on the rake face, and experimental tests were conducted to identify the most effective texture. The findings showed that using textured tools with micro-grooves perpendicular to the chip flow direction, with CNT-enriched nanofluid lubrication, resulted in significant reductions in main cutting force, built-up edge, and surface finish. The decreases were up to 32%, 37%, and 19%, respectively, compared to dry turning conditions.

Performance Evaluation of Micro-Textured Inserts Coupled With Solid Lubricants During the Sustainable Dry Machining of Inconel 825

Abstract In this research work, the turning of Inconel 825 has been carried out using uncoated and coated laser-textured hard tungsten carbide (WC) cutting inserts. The efficacy of uncoated textured inserts has been tried to improve by impregnating them with micro-sized MoS2 and nano-TiC powder paste. The results of coated and uncoated textured inserts have been compared with the plain uncoated tungsten carbide insert. The use of solid lubricant-impregnated textured tools and coated textured tools has significantly reduced the cutting forces and chip–tool interface friction as compared to plain and normal textured tools. Upon the SEM analysis, high adhesion over the rake face of the plain tool has been observed. The excessive adhesion over the rake surface has been observed over the normal textured tool due to the derivative cutting phenomena. The use of MoS2 and nano-TiC-impregnated textured tools has significantly reduced the material adhesion over the rake surface by eliminating the derivative cutting effect. The use of AlTiSiN-coated textured tools has also restricted the extent of work material adhesion over the rake surface of the cutting insert.

Modeling of oscillating bone sawing forces with instantaneous cutting speed and depth of cut

Oscillating bone sawing is a crucial procedure in orthopedic surgery, but excess sawing forces are often detrimental to implant fixation and postoperative patient recovery. Therefore, understanding and controlling sawing forces are critical. However, the conventional bone cutting model is not applicable to the oscillating sawing process, as it requires variable speed cutting with a negative rake angle, which is affected by the difference in viscoelasticity of the bone at different speeds. In this study, an oscillating sawing force model was developed that considered variations in cutting speeds and depth of cut for each saw tooth. A speed-related cutting force model, including ploughing force in the tool edge and rake face, was developed, considering the effect of speeds on fracture toughness and normal stress based on orthogonal cutting experiments. Moreover, the model accounted for each saw tooth's instantaneous depth of cut by considering the depth of elastic recovery and interference effect of adjacent saw teeth, based on a kinematic model of the saw tooth tip. The impact force in the blind groove cut and the acceleration effect on cutting force were also considered in the model. The proposed model accurately predicts sawing forces, offers insights for reducing them through design parameter modifications, and has potential applications in medical training simulations, robotic-assisted surgery, and the optimization of saw blade shapes or movement to reduce sawing forces.

Strain and phase evolution in TiAlN coatings during high-speed metal cutting: An in operando high-energy x-ray diffraction study

We report on phase and strain changes in Ti1-xAlxN (0 ≤ x ≤ 0.61) coatings on cutting tools during turning recorded in operando by high-energy x-ray diffractometry. Orthogonal cutting of AISI 4140 steel was performed with cutting speeds of 360–370 m/min. Four positions along the tool rake face were investigated as a function of time in cut. Formation of γ-Fe in the chip reveals that the temperature exceeds 727 °C between the tool edge and the middle of the contact area when the feed rate is 0.06 mm/rev. Spinodal decomposition and formation of wurtzite AlN occurs at the positions of the tool with the highest temperature for the x ≥ 0.48 coatings. The strain evolution in the chip reveals that the mechanical stress is largest closest to the tool edge and that it decreases with time in cut for all analyzed positions on the rake face. The strain evolution in the coating varies between coatings and position on the rake face of the tool and is affected by thermal stress as well as the applied mechanical stress. Amongst others, the strain evolution is influenced by defect annihilation and, for the coatings with highest Al-content (x ≥ 0.48), phase changes.

An investigation on the performance of bio-mimicked rake surface structured tool during machining of hard-to-cut materials

The current work seeks to improve the machining characteristics of tool by generation of various geometrical structures on cemented carbide tool's rake face. A total of three different structures: (a) bio-mimicked micro-crescent structure, (b) micro-dimple structure, and (c) micro-groove structure, are generated using laser micro-machining technique on rake surface of tool. Dry turning tests were performed using the structured tool and conventional tool during cutting of AISI 420 workpiece material. The effect of various geometrical textures on chip-tool contact area, surface roughness, cutting force, morphology of chip and residual stress have been compared with respect to conventional tool. Results indicate that crescent-shaped bio-mimicked structured tool indicated better cutting performance in decreasing contact area of chip-tool by 43.6%, tangential force by 15.38%, feed force by 20.22%, and average surface roughness by 8.81% relative to the conventional tool. The machined surface of structured tool also indicated lower generation of residual stress of 419.3 MPa in cutting direction and 316.9 MPa in feed direction relative to 608.3 MPa in cutting and 375.5 MPa in feed direction using conventional tool machined surface. Segmented chips were produced during all machining conditions, and crescent-shaped structured tool indicated least chip reduction coefficient of 1.08 compared to 1.57 in the case of conventional tool. The results of the current study are very essential for expanding the application of bio-mimicked structured cutting tools for cutting different hard to machine materials.

Discrete wavelet transforms analysis of vibration signals for correlating tool wear in diamond turning of additive manufactured Ti-6Al-4V alloy

Ultra-precision machining (UPM) of Ti-6Al-4V alloy is widely regarded as a challenging material processing due to excessive tool wear and chemical reactivity of the tool and workpiece. Tool wear has a significant influence on the surface quality and also causes damage to the substrate. Therefore, it is critical to consider the tool condition during diamond turning, especially as precision machining moves toward intelligent systems. Consequently, there is a need for effective ways for in-process tool wear monitoring in UPM. This study aims to monitor the diamond tool wear using time-frequency-based wavelet analysis on vibrational signals acquired during the machining of Additively Manufactured (AM) Ti6Al4V alloy. The analysis employed Daubechies wavelet (db4, level 8) to establish a correlation between the Standard Deviation (SD) of the magnitude in the decomposed vibrational signal obtained from both the fresh and used tools. The analysis revealed that at a feed rate of 1 mm/min, the change in SD is 32.3% whereas at a feed rate of 5 mm/min, the change in SD is 8.4%. Furthermore, the flank wear and microfractures are observed using a scanning electron microscope on the respective flank and rake face of the diamond tool.

Comparison of the performance of the internally cooled tool in closed circuit against standard PCBN tools in turning AISI D6 hardened

Machining is a widely used manufacturing process that involves removing material from a workpiece. During this process, more than 95 % of the mechanical energy from the machine tool's electrical motor is converted into heat. This can cause the cutting tool's temperature to soar to extremely high levels, reaching up to 1200 °C or even higher, especially when working with hardened steels. To cool down the machining region, cutting fluids are commonly employed in industries. However, these fluids are not considered sustainable because they pose environmental pollution risks, are costly, challenging to dispose of properly, and can also be hazardous to operators' health. Moreover, in some applications, cutting fluids are not recommended. Considering these issues, this research aims to propose and test a more sustainable approach. The method involves using a closed-circuit system where a mixture of water and ethylene glycol circulates internally in polycrystalline cubic boron nitride (PCBN) tools. These tools are employed in the turning operation of AISI D6 hardened steel and are compared with conventional dry machining. The study utilizes a design of experiment (DOE) and analysis of variance (ANOVA) to plan and analyze the results with statistical reliability. Key output variables considered include cutting temperature, tool life, cutting forces, and surface roughness. The implementation of the internally cooled tool (ICT) system has shown significant benefits. It notably reduces the temperature of the tool's rake face, as measured using a thermographic camera. Despite not being the main variable affecting the maximum temperature, the cooling system plays a crucial role in achieving these improvements. The ICT system also substantially increases the tool life in comparison to conventional dry machining across all tested cutting conditions. While the feed rate remains the most influential factor affecting cutting forces due to increased cutting area, the cooling system also plays a significant role. The ICT system, with reduced temperatures, performs better in this regard. As for surface roughness, the condition of the tool edge emerges as the sole significant factor. Surprisingly, the worn tool provides better surface finishing due to the presence of crater wear. With conventional dry machining, higher cutting temperatures lead to increased tool wear, primarily caused by abrasion and attrition.

Research on Wear of Micro-Textured Tools in Turning GH4169 during Spray Cooling

In this study, the wear resistance of micro-textured tools was explored. Micro-textured tools with different morphologies were used in turning GH4169 during spray cooling. The tool wear on the rake face of the different micro-texture morphologies was investigated through simulation and experiments. Firstly, based on the existing research on bionics, micro-textures with five different morphologies were designed on the rake face of carbide tools. A simulation model of cutting GH4169 during spray cooling was established, and the tools with designed micro-textures were used in it. The influence of the different micro-texture morphologies on the tool wear was analyzed. Secondly, the designed micro-textured tools with five different morphologies were produced using a femtosecond laser. Cutting experiments were conducted using the micro-textured tools during spray cooling. The wear area of the rake face was measured based on the infinitesimal method, and the optimal morphology with the best anti-wear ability was obtained. This study provides technical support for the design and development of micro-textured tools with an improved cutting performance, and contribute to the promotion and application of micro-textured tools.

Nonlinearity and periodicity in machining carbon fiber reinforced polymer

In the machining of carbon fiber reinforced polymer (CFRP) materials, the relationship between the cutting forces and uncut chip thickness can be linear or nonlinear, depending on the fiber orientation ranges. In addition, the variation of cutting forces in two consecutive cuts is periodic at a certain fiber orientation of 120 deg and the uncut chip thicknesses of 30μm60μm. It is suggested that the material removal rate changes even for the same uncut chip thickness in consecutive cuts, such as milling and drilling. Through orthogonal experiments for unidirectional CFRP at various fiber orientations and uncut chip thicknesses, this study aims to analyze the observed nonlinearity and periodicity of cutting forces which occur at certain fiber orientation and uncut chip thickness. It is found that both the nonlinearity and periodicity are primarily dependent on the machined surface damage left by the previous cut. This damage state varies with the uncut chip thickness and is influenced by the interaction between the material deformations at the tool rake face and flank face. Thus, the reported findings in the chip formation and cutting force generation reported by this study can guide the tooling and process planning to enhance the machining performance for CFRP.

Ultra-precision cutting characteristics of binderless tungsten carbide by in-heat-process laser-assisted diamond machining

The study systematically investigates the ductile-brittle transition behavior, material removal mechanism, and end-face turning performance of binderless tungsten carbide using in-process-heat laser-assisted diamond machining. Both numerical simulation analysis and experimental cutting experiments were conducted. To ensure that the laser loading condition and energy distribution were consistent with the ray-tracing simulation and spatial power density distribution measurement, a practical thermal simulation model was created with a semicircular Gaussian distribution. This model was then used to study the temperature distribution, and the material's thermal transient response to laser radiation was also analyzed in detail. The high-temperature nanoindentation revealed increased ductile machinability due to plastic deformation, microhardness reduction, and Young's modulus decrease at elevated temperatures, providing fundamental support for the ductile-brittle transition behavior. The ductile-brittle transition depth increased by 247.20% compared to conventional groove cutting without laser assistance. The cutting forces during groove cutting decreased gradually with increasing laser power, but excess laser power may cause fluctuations in cutting forces due to surface high-temperature oxidation and potential thermal expansion. The ductile-brittle transition dynamic behavior analysis, based on the discrete wavelet transform algorithm, showed good consistency with the conventional groove profile analysis. The friction coefficient between the tool rake face and chip decreased with increasing laser power, which facilitated improving the tool life. The statistical analysis of end-face turning experiments based on the Taguchi method indicated that laser power was the most significant factor affecting surface quality. The verification turning experiments validated the determined optimal parametric combination. Ultra-high-quality spherical lenses were obtained in ductile cutting mode with slightly less tool wear, a more homogeneous finish (less than 3 nm in Sa), and more outstanding form accuracy (133 nm in PV) compared to conventional turning without laser assistance.

Wear behavior of SiAlON ceramic tool and its effects during high-speed cutting

Nickel-based superalloys are widely employed in aerospace and other fields on account of excellent performance. However, the tool is easily worn out in cutting of superalloys, which will deteriorate the surface quality and lower the service life of the components. In this paper, the effect of ceramic tool wear on surface integrity during high-speed turning of superalloy GH4169 was studied. The results demonstrate that tool wear raises cutting temperature and cutting force. The wear mechanisms of the rake face of the ceramic tool are adhesive wear and oxidation wear, and the wear mechanisms of the flank face are adhesive wear, oxidation wear and abrasive wear. The enhancement effect of tool wear on thermal effect is greater than that on mechanical effect, which forms a larger tensile residual stress on the machined surface. In addition, tool wear increases the thickness of the plastic deformation layer, raising the KAM value from 0.43° to 0.63° at a cutting speed of 200 m/min.