The Experts below are selected from a list of 9219 Experts worldwide ranked by ideXlab platform
Kui Liu - One of the best experts on this subject based on the ideXlab platform.
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Ductile Mode cutting characteristics
2020Co-Authors: Kui Liu, Hao Wang, Xinquan ZhangAbstract:Ductile Mode cutting characteristics and material removal mechanism of brittle material are discussed using tungsten carbide as an example work material in this chapter. Grooving and milling tests are designed and conducted to investigate their cutting Modes. Experimental results indicate that there is a transition from Ductile Mode cutting to brittle Mode cutting in grooving of tungsten carbide when depth of cut is increased from zero to a certain value. SEM observations on machined work surfaces show that there are three cutting Modes in grooving of brittle material as depth of cut being increased: Ductile Mode cutting, semi-brittle Mode cutting and brittle Mode cutting. Cutting Modes is identified and classified by machined surface texture and chip formation. In Ductile Mode cutting of tungsten carbide, thrust force Ft is much larger than cutting force Fc, which results in a large compressive stress in cutting zone. Large compressive stress and shear stress could shield the growth of pre-existing flaws in work material by suppressing its stress intensity factor KI, such that KI < KC making work material is able to undertake a large cutting stress without fracturing to achieve Ductile Mode cutting. SEM and EDS examinations on cutting tools indicate that tool wear mainly occurs on flank face and tool wear mechanisms are dominated by diffusion, adhesion and abrasion in cutting of tungsten carbide.
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Ductile Mode cutting of glass
2020Co-Authors: Kui Liu, Hao Wang, Xinquan ZhangAbstract:Recently, the industrial application of glass has increased enormously because of its excellent and unique mechanical, physical, chemical and optical properties. However, machining of glass is still a major problem for the manufacturing industry since it is very brittle and high hardness. In this chapter, grooving and cutting tests of soda-lime glass are conducted to evaluate its cutting performance using an ultra-precision lathe with a single crystal diamond tool. The machined workpiece surface topography, chip formation and surface roughness are examined using a SEM, AFM and white light interferometer. Tool wear is measured using OMIS. Experimental results indicate that Ductile Mode cutting of soda-lime glass is achieved when the undeformed chip thickness being less than a critical value. Ultrasonic vibration assisted cutting is employed to improve Ductile Mode cutting performance of soda-lime glass. Continuous layer chip and smooth surface are obtained in ultrasonic vibration assisted cutting of soda-lime glass, which largely improve its machinability in Ductile Mode cutting. But extremely short tool life is the main constrain for realizing the ultrasonic vibration assisted Ductile Mode cutting of glass in industry.
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Ductile Mode cutting of silicon
2020Co-Authors: Kui Liu, Hao Wang, Xinquan ZhangAbstract:In wafer fabrication, most machining processes such as slicing, edge grinding, finishing, lapping, polishing, back thinning and dicing, are based on grinding or/and abrasive process, which always generate micro cracks and subsurface damage. In this chapter, theoretical analysis on Ductile Mode cutting of silicon wafer shows that machined silicon surface with free of fracture and nanometer scale surface roughness can be achieved when dislocation dominates its chip formation rather than crack propagation. Nanometric cutting of silicon wafers using an ultra-precision CNC lathe with single crystal diamond cutters are carried out to investigate the tool edge radius effect on critical undeformed chip thickness and verify Ductile Mode cutting performance of silicon wafer. Machined workpiece surfaces and used diamond tools are examined using a scanning electron microscope (SEM), transmission electron microscopy (TEM) and atomic force microscope (AFM). Experimental results from the nanometric cutting tests indicate that in cutting of silicon wafers, there is a critical undeformed chip thickness, at or below which chip formation is under Ductile Mode cutting generating continuous chips. And critical undeformed chip thickness differs when cutting of silicon wafers using diamond cutters with different tool edge radius. Larger diamond tool edge radius, larger critical undeformed chip thickness. But there is an upper bound for diamond tool edge radius, above which chip formation is changed from Ductile Mode to brittle Mode even though undeformed chip thickness remains to be smaller than tool edge radius. Experimental results are found to well substantiate the analytical findings and nanometric Ductile Mode cutting of silicon wafer is successfully achieved under certain cutting conditions.
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Ductile Mode cutting of tungsten carbide
2020Co-Authors: Kui Liu, Hao Wang, Xinquan ZhangAbstract:Cutting experiments are carried out to evaluate the cutting performance of tungsten carbide under nanometer scale chip thickness using a 5-axis CNC machining centre with CBN tools. The cutting forces are measured using a three-component dynamometer. Machined workpiece surface topography, chip formation, and tool wear are examined using an OMIS and SEM. Tool flank wear VBmax is also measured using the OMIS. Surface roughness is measured using a stylus profiler. Experimental results indicate that radial force Fx is much larger than tangential force Fz and axial force Fy. Under different cutting conditions, three types of surfaces of machined workpiece are achieved: Ductile Mode cutting surface, semi fractured surface and fractured surface. Continuous chips and discontinuous chips are formed under different cutting conditions. Surface roughness increases monotonically when the depth of cut and feed rate being increased. Tool wear occurs mainly on the flank face in Ductile Mode cutting of tungsten carbide and tool wear mechanisms are dominated by abrasion, adhesion and diffusion wear. SEM observations on machined workpiece surfaces and chip formation indicate that Ductile Mode cutting is mainly determined by undeformed chip thickness when the tool cutting edge radius is fixed. Ductile Mode cutting of tungsten carbide is achieved when undeformed chip thickness is less than a critical value.
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Modelling of Ductile Mode cutting
2020Co-Authors: Kui Liu, Hao Wang, Xinquan ZhangAbstract:Although the demand for industrial applications for brittle material growing rapidly, the manufacturing of brittle material for making precise components is very challenging due to its poor machinability and brittleness. In this chapter, theoretical analyses are given based on brittle material’s mechanical properties as the functions of temperature and on critical conditions for Ductile Mode chip formation in cutting of brittle material. An energy Model for Ductile Mode chip formation in cutting of brittle material is developed, in which critical undeformed chip thickness for Ductile chip formation in cutting of brittle material is predicted from material’s mechanical properties, or tool geometry and cutting conditions used. Experiments are conducted on conventional grooving of tungsten carbide material to verify the proposed Model for predicting critical undeformed chip thickness, which shows a substantial agreement between the predicted value and experimental results.
Xinquan Zhang - One of the best experts on this subject based on the ideXlab platform.
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Ultrasonic Vibration Assisted Ductile Mode Cutting
Ductile Mode Cutting of Brittle Materials, 2020Co-Authors: Kiu Liu, Hao Wang, Xinquan ZhangAbstract:It has been well known that ultrasonic vibration assisted cutting (UVC) is able to improve the machining performance for various material removal processes. For machining of brittle material, UVC has also been proven useful in improving surface integrity and increasing tool life by significantly increasing critical undeformed chip thickness for Ductile-to-brittle transition. This chapter presents an analytical Model to predict critical undeformed chip thickness in UVC of brittle material, based on the variation of specific cutting energy for prediction of Ductile-to-brittle transition in nano-machining. Vibration parameters are taken into consideration in addition to work material intrinsic properties, tool geometry and machining parameters in predicting critical undeformed chip thickness. A series of cutting tests on single crystal silicon workpiece, using a single crystal diamond tool with different nominal cutting speeds, are conducted to verify the proposed theoretical Model.
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Ultrasonic Vibration Assisted Cutting of Tungsten Carbide
Ductile Mode Cutting of Brittle Materials, 2020Co-Authors: Kiu Liu, Hao Wang, Xinquan ZhangAbstract:In this chapter, ultrasonic vibration assisted cutting is conducted to investigate the effect of various cutting conditions such as vibration Mode and amplitude, diamond type, cutting speed, feed rate and depth of cut, on Ductile Mode cutting of tungsten carbide such as critical depth of cut, cutting force, chip formation, tool wear and surface integrity. Cutting forces are measured using a three-component dynamometer, critical depth of cut is measured using a stylus profilometer, machined surface integrity and chip formation are examined using an SEM, and tool wear is examined using an OMIS. It is found that critical depth of cut for the transition from Ductile Mode cutting to brittle Mode cutting in 1D ultrasonic vibration assisted grooving is several times larger than that in the conventional grooving. Lower thrust directional amplitude in 2D ultrasonic vibration leads to less brittle fracture generated on the machined surface of tungsten carbide, and 1D ultrasonic vibration with no thrust directional vibration leads to minimum brittle fracture and less diamond tool wear. Nano-polycrystalline diamond with isotropic mechanical properties does not perform better than single crystal diamond as tool material in terms of tool flank wear in ultrasonic vibration assisted turning of tungsten carbide. Radial cutting force F _ x is much larger than tangential cutting force F _ z and axial cutting force F _ y . Cutting speed has no significant effect on Ductile chip formation Mode. Ductile Mode cutting is achieved when maximum undeformed chip thickness is smaller than a critical value. And the larger critical depth of cut for 1D ultrasonic vibration assisted grooving of tungsten carbide implies that ultrasonic vibration could be used to improve Ductile Mode cutting performance of brittle material.
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Ductile Mode cutting characteristics
2020Co-Authors: Kui Liu, Hao Wang, Xinquan ZhangAbstract:Ductile Mode cutting characteristics and material removal mechanism of brittle material are discussed using tungsten carbide as an example work material in this chapter. Grooving and milling tests are designed and conducted to investigate their cutting Modes. Experimental results indicate that there is a transition from Ductile Mode cutting to brittle Mode cutting in grooving of tungsten carbide when depth of cut is increased from zero to a certain value. SEM observations on machined work surfaces show that there are three cutting Modes in grooving of brittle material as depth of cut being increased: Ductile Mode cutting, semi-brittle Mode cutting and brittle Mode cutting. Cutting Modes is identified and classified by machined surface texture and chip formation. In Ductile Mode cutting of tungsten carbide, thrust force Ft is much larger than cutting force Fc, which results in a large compressive stress in cutting zone. Large compressive stress and shear stress could shield the growth of pre-existing flaws in work material by suppressing its stress intensity factor KI, such that KI < KC making work material is able to undertake a large cutting stress without fracturing to achieve Ductile Mode cutting. SEM and EDS examinations on cutting tools indicate that tool wear mainly occurs on flank face and tool wear mechanisms are dominated by diffusion, adhesion and abrasion in cutting of tungsten carbide.
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Ductile Mode cutting of glass
2020Co-Authors: Kui Liu, Hao Wang, Xinquan ZhangAbstract:Recently, the industrial application of glass has increased enormously because of its excellent and unique mechanical, physical, chemical and optical properties. However, machining of glass is still a major problem for the manufacturing industry since it is very brittle and high hardness. In this chapter, grooving and cutting tests of soda-lime glass are conducted to evaluate its cutting performance using an ultra-precision lathe with a single crystal diamond tool. The machined workpiece surface topography, chip formation and surface roughness are examined using a SEM, AFM and white light interferometer. Tool wear is measured using OMIS. Experimental results indicate that Ductile Mode cutting of soda-lime glass is achieved when the undeformed chip thickness being less than a critical value. Ultrasonic vibration assisted cutting is employed to improve Ductile Mode cutting performance of soda-lime glass. Continuous layer chip and smooth surface are obtained in ultrasonic vibration assisted cutting of soda-lime glass, which largely improve its machinability in Ductile Mode cutting. But extremely short tool life is the main constrain for realizing the ultrasonic vibration assisted Ductile Mode cutting of glass in industry.
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Ductile Mode cutting of silicon
2020Co-Authors: Kui Liu, Hao Wang, Xinquan ZhangAbstract:In wafer fabrication, most machining processes such as slicing, edge grinding, finishing, lapping, polishing, back thinning and dicing, are based on grinding or/and abrasive process, which always generate micro cracks and subsurface damage. In this chapter, theoretical analysis on Ductile Mode cutting of silicon wafer shows that machined silicon surface with free of fracture and nanometer scale surface roughness can be achieved when dislocation dominates its chip formation rather than crack propagation. Nanometric cutting of silicon wafers using an ultra-precision CNC lathe with single crystal diamond cutters are carried out to investigate the tool edge radius effect on critical undeformed chip thickness and verify Ductile Mode cutting performance of silicon wafer. Machined workpiece surfaces and used diamond tools are examined using a scanning electron microscope (SEM), transmission electron microscopy (TEM) and atomic force microscope (AFM). Experimental results from the nanometric cutting tests indicate that in cutting of silicon wafers, there is a critical undeformed chip thickness, at or below which chip formation is under Ductile Mode cutting generating continuous chips. And critical undeformed chip thickness differs when cutting of silicon wafers using diamond cutters with different tool edge radius. Larger diamond tool edge radius, larger critical undeformed chip thickness. But there is an upper bound for diamond tool edge radius, above which chip formation is changed from Ductile Mode to brittle Mode even though undeformed chip thickness remains to be smaller than tool edge radius. Experimental results are found to well substantiate the analytical findings and nanometric Ductile Mode cutting of silicon wafer is successfully achieved under certain cutting conditions.
M. Rahman - One of the best experts on this subject based on the ideXlab platform.
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study of the upper bound of tool edge radius in nanoscale Ductile Mode cutting of silicon wafer
The International Journal of Advanced Manufacturing Technology, 2010Co-Authors: Minbo Cai, M. Rahman, Steven Y. LiangAbstract:In cutting of brittle materials, experimentally it was observed that there is an upper bound of tool cutting edge radius, beyond which, although the undeformed chip thickness is smaller than the tool cutting edge radius, the Ductile Mode cutting cannot be achieved. However, why there is an upper bound of tool cutting edge radius in nanoscale Ductile Mode cutting of brittle materials has not been fully understood. In this study, based on the tensile stress distribution and the characteristics of the distribution obtained from molecular dynamics simulation of nanoscale Ductile cutting of silicon, an approximation for the tensile stress distribution was obtained. Using this tensile stress distribution with the principles of geometrical similarity and fracture mechanics, the critical conditions for the crack initiation have been determined. The result showed that there is a critical tool cutting edge radius, beyond which crack initiation can occur in the nanoscale cutting of silicon, and the chip formation Mode is transferred from Ductile to brittle. That is, this critical tool cutting edge radius is the upper bound of the tool cutting edge radius for Ductile Mode cutting of silicon.
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Characteristics of ultrasonic vibration-assisted Ductile Mode cutting of tungsten carbide
The International Journal of Advanced Manufacturing Technology, 2008Co-Authors: Kiu Liu, M. RahmanAbstract:In this study, investigations were carried out to evaluate the characteristics of ultrasonic vibration-assisted cutting of tungsten carbide material using a CNC lathe with CBN tool inserts. The cutting forces were measured using a three-component dynamometer, and the machined workpiece surfaces and chip formation were examined using a SEM. The experimental results showed that the radial force F _ x was much larger than the tangential force F _ z and axial force F _ y . The SEM observations on the machined workpiece surfaces and chip formation indicated that the critical condition for Ductile Mode cutting of tungsten carbide was mainly the maximum undeformed chip thickness when the tool cutting edge radius was fixed, that is, the Ductile Mode cutting can be achieved when the maximum undeformed chip thickness was smaller than a critical value. Corresponding to the chip formation Mode (Ductile or brittle), three types of the machined workpiece surfaces were obtained: fracture free surface, semi-fractured surface and fractured surface. It was also found that the cutting speed has no significant effect on the Ductile chip formation Mode.
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performance of single crystal diamond tools in Ductile Mode cutting of silicon
Journal of Materials Processing Technology, 2007Co-Authors: Sharif M Uddin, K H W Seah, M. Rahman, Kui LiuAbstract:Abstract In this study, Ductile Mode cutting of silicon wafer materials has been carried out using an ultra-precision lathe with single crystal diamond cutters and the wear characteristics of the tool and the effect of its different diamond crystal orientations were investigated. Experimental results indicated that wear occurred mainly on the flank face of the tool and the wear pattern was typically mechanical abrasive wear, adhesive wear and possible thermo-chemical wear. At higher cutting distance, crater wear with small grooves in the vicinity of cutting edge was observed on the tool rake face. However, given the highly anisotropic nature in properties of diamond, wear resistance of a diamond tool varies with the crystal planes as well as crystal directions on the same plane. From this study, it is found that in terms of tool flank wear (VBmax) resistance, the tool life of the diamond cutter with crystal orientations {1 0 0} as the rake and {1 1 0} as the flank planes, was much longer than those of the diamond cutters with other crystal orientations as the rake and flank planes.
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the effect of the cutting edge radius on a machined surface in the nanoscale Ductile Mode cutting of silicon wafer
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2007Co-Authors: S Arefin, M B Cai, Kui Liu, M. Rahman, A TayAbstract:AbstractIn this study, the effect of the cutting edge radius on a machined surface and subsurface in the nanoscale Ductile Mode cutting of silicon wafer is investigated through cutting tests using tools with edge radii ranging from 23 nm to 807 nm. The machined surface is examined using SEM, AFM, and Formtracer, with an etching technique used for SEM observation. The results show that if the cutting edge radius does not exceed a certain upper bound value, and the undeformed chip thickness is less than the cutting edge radius, it is possible to achieve both a surface and a subsurface free of cracks. Based on the molecular dynamics simulation of the nanoscale Ductile Mode cutting process of monocrystalline silicon wafer, it is found that the critical upper bound for the cutting edge radius in the Ductile Mode chip formation relates to the stress condition in the cutting region. The shear stress decreases as the tool edge radius is increased. As the cutting edge radius increases beyond the limit, the insuffi...
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A study of the effect of tool cutting edge radius on Ductile cutting of silicon wafers
The International Journal of Advanced Manufacturing Technology, 2006Co-Authors: X P Li, M. RahmanAbstract:Ductile Mode cutting of silicon wafers can be achieved under certain cutting conditions and tool geometry. An experimental investigation of the critical undeformed chip thickness in relation to the tool cutting edge radius for the brittle-Ductile transition of chip formation in cutting of silicon wafers is presented in this paper. Experimental tests for cutting of silicon wafers using diamond tools of different cutting edge radii for a range of undeformed chip thickness are conducted on an ultra-precision lathe. Both Ductile and brittle Mode of chip formation processes are observed in the cutting tests. The results indicate that Ductile cutting of silicon can be achieved at certain values of the undeformed chip thickness, which depends on the tool cutting edge radius. It is found that in cutting of silicon wafers with a certain tool cutting edge radius there is a critical value of undeformed chip thickness beyond which the chip formation changes from Ductile Mode to brittle Mode. The Ductile-brittle transition of chip formation varies with the tool cutting edge radius. Within the range of cutting conditions in the present study, it has also been found that the larger the cutting edge radius, the larger the critical undeformed chip thickness for the Ductile-brittle transition in the chip formation.
X P Li - One of the best experts on this subject based on the ideXlab platform.
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High-pressure phase transformation as the mechanism of Ductile chip formation in nanoscale cutting of silicon wafer:
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2007Co-Authors: X P LiAbstract:AbstractIn nanoscale cutting of silicon wafer, it has been found that under certain conditions Ductile Mode chip formation can be achieved. In order to understand the mechanism of the Ductile chip formation, experiments and molecular dynamics (MD) simulations have been conducted in this study. The results of MD simulations of nanoscale cutting of silicon showed that because of the high hydrostatic pressure in the chip formation zone, there is a phase transformation of the monocrytslline silicon from diamond cubic structure to both β silicon and amorphous phase in the chip formation zone, which results in plastic deformation of the workpiece material in the chip formation zone, as observed in experiments. The results further showed that although from experimental observation the plastic deformation in the Ductile Mode cutting of silicon is similar to that in cutting of Ductile materials, such as aluminium, in Ductile Mode cutting of silicon it is the phase transformation of silicon rather than atomic dislo...
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Study of the temperature and stress in nanoscale Ductile Mode cutting of silicon using molecular dynamics simulation
Journal of Materials Processing Technology, 2007Co-Authors: X P LiAbstract:Abstract In nanoscale cutting of brittle materials, it has been found that there is a brittle–Ductile transition when the cutting tool edge radius is reduced to nanoscale and the undeformed chip thickness is smaller than the tool edge radius. In order to understand the mechanism of the brittle–Ductile transition, the cutting characteristics, such as stress and temperature in the cutting region, have to be investigated. However, since the machining size is very small, on the nanoscales, it's very difficult to measure the temperature and stress in the chip formation zone experimentally. In this study, the molecular dynamics (MD) method is employed to Model and simulate the nanoscale Ductile Mode cutting of monocrystalline silicon wafer. The MD simulation results show that the temperature rise in the cutting zone will affect the diamond tool. In the cutting process, the thrust force is larger than the cutting force. As the tool cutting edge radius increases, the shear stress in the workpiece material around the cutting edge will decrease. When the shear stress is so low that it is insufficient to sustain dislocation emission in the chip formation zone, crack propagation becomes dominating. Consequently, the chip formation Mode changes from Ductile to brittle.
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A study of the effect of tool cutting edge radius on Ductile cutting of silicon wafers
The International Journal of Advanced Manufacturing Technology, 2006Co-Authors: X P Li, M. RahmanAbstract:Ductile Mode cutting of silicon wafers can be achieved under certain cutting conditions and tool geometry. An experimental investigation of the critical undeformed chip thickness in relation to the tool cutting edge radius for the brittle-Ductile transition of chip formation in cutting of silicon wafers is presented in this paper. Experimental tests for cutting of silicon wafers using diamond tools of different cutting edge radii for a range of undeformed chip thickness are conducted on an ultra-precision lathe. Both Ductile and brittle Mode of chip formation processes are observed in the cutting tests. The results indicate that Ductile cutting of silicon can be achieved at certain values of the undeformed chip thickness, which depends on the tool cutting edge radius. It is found that in cutting of silicon wafers with a certain tool cutting edge radius there is a critical value of undeformed chip thickness beyond which the chip formation changes from Ductile Mode to brittle Mode. The Ductile-brittle transition of chip formation varies with the tool cutting edge radius. Within the range of cutting conditions in the present study, it has also been found that the larger the cutting edge radius, the larger the critical undeformed chip thickness for the Ductile-brittle transition in the chip formation.
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Tool wear characteristics and their effects on nanoscale Ductile Mode cutting of silicon wafer
Wear, 2005Co-Authors: X P Li, T. He, Mustafizur RahmanAbstract:Nanoscale Ductile Mode cutting of single crystalline silicon is a very promising technology for fracture free machining of silicon wafers. In the technology, the tool edge radius is required to on nanoscale for the Ductile chip formation Mode. Therefore, one of the main concerns with the implementation of such a technology is the tool wear and its effect on chip formation Mode. In this study, the variation of tool geometry due to tool wear and its influence on the nanoscale Ductile Mode cutting of silicon wafer with single crystalline diamond tools is investigated and analyzed. The tool shape and cutting edge radius before and after cutting are measured using a non-destructive nano-indentation method. Variations of the cutting forces with tool wear during cutting are also investigated. It is found that the tool cutting edges undergo two processes simultaneously. One is the wear of material on the tool main cutting edge, which increases the main cutting edge radius, but leaves the shape of the main cutting edge unchanged, enhancing the conditions for Ductile Mode chip formation. The other one is the generation of nano or micro grooves at the tool flank, which forms sub-cutting edges of much smaller radii on the main cutting edge. As the grooves become deeper and deeper, the sub-cutting edges extend towards the tool rake face ultimately becoming the dominating cutting edge of much smaller radius. In such a way these sub-cutting edges tend to change the cutting Mode from Ductile to brittle.
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Study of Ductile Mode cutting in grooving of tungsten carbide with and without ultrasonic vibration assistance
The International Journal of Advanced Manufacturing Technology, 2004Co-Authors: X P Li, M. RahmanAbstract:In this study, Ductile Mode chip formation in conventional cutting and ultrasonic vibration assisted cutting of tungsten carbide workpiece material has been investigated through experimental grooving tests using CBN tools on a CNC lathe. The experimental results show that as the depth of cut was increased there was a transition from Ductile Mode to brittle Mode chip formation in grooving both with and without ultrasonic vibration assistance. However, the critical value of the depth of cut for Ductile Mode cutting with ultrasonic vibration assistance was much larger than that without ultrasonic vibration assistance. The ratio of the volume of removed material to the volume of the machined groove, f _ ab , was used to identify the Ductile Mode and brittle Mode of chip formation in the grooving tests, in which f _ ab 1 indicates brittle Mode chip formation. For the same radius of tool cutting edge, the value of f _ ab at the Ductile-brittle transition region either with or without ultrasonic vibration was less than 1. However, the f _ ab value with ultrasonic vibration assistance was close to 1. The experimental results demonstrate that ultrasonic vibration assisted cutting can be used to improve the Ductile Mode cutting performance of tungsten carbide work material.
Xiaoping Li - One of the best experts on this subject based on the ideXlab platform.
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Characteristics of dynamic hard particles in nanoscale Ductile Mode cutting of monocrystalline silicon with diamond tools in relation to tool groove wear
Wear, 2007Co-Authors: Xiaoping LiAbstract:Abstract In nanoscale Ductile Mode cutting of the monocrystalline silicon wafer, micro/nano groove wear on the diamond cutting tool flank face is often observed, which is beyond the understanding based on conventional cutting processes because the silicon workpiece material is monocrystalline with the hardness lower than that of the diamond cutting tool at room temperature. From the investigation of such a phenomenon, a concept of “dynamic hard particles” generated in the chip formation zone as a result of silicon phase transformation from monocrystalline to amorphous was proposed. It was believed that the “dynamic hard particles” caused the groove wear at the tool flank. In this study, the characteristics of such “dynamic hard particles” and their relationship with the diamond tool groove wear have been investigated through molecular dynamics (MD) simulation of nanoscale Ductile Mode cutting of monocrystalline silicon with diamond tools. The results show that during the cutting process, due to the workpiece material phase transformation from monocrystalline to amorphous, which results in the existence of silicon atom groups with shorter bond lengths in the chip formation zone, “dynamic hard particles” having a dynamic and uneven distribution over the entire chip formation zone are formed. The distribution changes over time and cutting stages. When the cutting runs into a steady state, the “dynamic hard particles” are mostly distributed in the lower portion of chip formation zone, contributing directly to three body abrasions on the tool flank face, causing groove wear at tool flank. The dynamic distribution of the “dynamic hard particles” also causes the uncertainty of the groove wear locations at the tool flank.
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Characteristics of Ductile Mode chip formation in nanoscale cutting of brittle materials
International Journal of Abrasive Technology, 2007Co-Authors: Xiaoping LiAbstract:In this paper, a comprehensive study of the machining characteristics of nanoscale Ductile Mode cutting of brittle materials is presented, covering the critical cutting conditions for the Ductile Mode of chip formation, cutting conditions for crack initiation in the chip formation zone, effect of the cutting edge radius, machined workpiece surface and subsurface damage, effect of ultrasonic vibration assistance, mechanism of nanoscale Ductile Mode chip formation, cutting forces, tool wear and dynamic hard particles in the chip formation zone. Systematic experiments for nanoscale cutting of a number of brittle materials, including tungsten carbide, silicon and glass, are conducted and Molecular Dynamics (MD) Modelling and simulation for nanoscale cutting of monocrystalline silicon are carried out. The results are shown in detail in the paper.
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Molecular dynamics Modelling and simulation of nanoscale Ductile cutting of silicon
Journal of Computer Applications in Technology, 2007Co-Authors: Xiaoping LiAbstract:A simulation system for nanoscale Ductile Mode cutting of monocrystalline silicon has been developed in thi study using the Molecular Dynamics (MD) method for better understanding of the Ductile Mode cutting mechanism. In the Model of this simulation system, the initial atom positions of silicon workpiece material are arranged according to the crystal lattice structure, the atomic interactive actions of silicon are based on the Tersoff potential, the diamond cutting tool is assumed to be undeformable, the tool cutting edge is realistically Modelled to have a finite radius, and the motions of the atoms in the chip formation zone are determined by Newton's equations of motion. The simulated variation of the cutting forces with the tool cutting edge radius is compared with the results of experimental cutting tests to substantiate the developed simulation system and the results show a good agreement with analytical findings.
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Study of the mechanism of nanoscale Ductile Mode cutting of silicon using molecular dynamics simulation
International Journal of Machine Tools & Manufacture, 2007Co-Authors: Xiaoping LiAbstract:Abstract In cutting of brittle materials, it was observed that there is a brittle-Ductile transition when two conditions are satisfied. One is that the undeformed chip thickness is smaller than the tool edge radius; the other is that the tool cutting edge radius should be small enough—on a nanoscale. However, the mechanism has not been clearly understood. In this study, the Molecular Dynamics method is employed to Model and simulate the nanoscale Ductile Mode cutting of monocrystalline silicon wafer. From the simulated results, it is found that when the Ductile cutting Mode is achieved in the cutting process, the thrust force acting on the cutting tool is larger than the cutting force. As the undeformed chip thickness increases, the compressive stress in the cutting zone decreases, giving way to crack propagation in the chip formation zone. As the tool cutting edge radius increases, the shear stress in the workpiece material around the cutting edge decreases down to a lower level, at which the shear stress is insufficient to sustain dislocation emission in the chip formation zone, and crack propagation becomes dominating. Consequently, the chip formation Mode changes from Ductile to brittle.
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Study of the Mechanism of Groove Wear of the Diamond Tool in Nanoscale Ductile Mode Cutting of Monocrystalline Silicon
Journal of Manufacturing Science and Engineering-transactions of The Asme, 2006Co-Authors: Xiaoping LiAbstract:In nanoscale Ductile Mode cutting of the monocrystalline silicon wafer, micro-, or nano-grooves on the diamond cutting tool flank face are often observed, which is beyond the understanding based on conventional cutting processes because the silicon workpiece material is monocrystalline and the hardness is lower than that of the diamond cutting tool at room temperature. In this study, the mechanism of the groove wear in nanoscale Ductile Mode cutting of monocrystalline silicon by diamond is investigated by molecular dynamics simulation of the cutting process. The results show that the temperature rise in the chip formation zone could soften the material at the flank face of the diamond cutting tool. Also, the high hydrostatic pressure in the chip formation region could result in the workpiece material phase transformation from monocrystalline to amorphous, in which the material interatomic bond length varies, yielding atom groups of much shorter bond lengths. Such atom groups could be many times harder than that of the original monocrystalline silicon and could act as "dynamic hard particles " in the material. Having the dynamic hard particles ploughing on the softened flank face of the diamond tool, the micro-/nanogrooves could be formed, yielding the micro-/nanogroove wear as observed.
