The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Andrew Cox - One of the best experts on this subject based on the ideXlab platform.
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brittle ductile transition during Diamond Turning of single crystal silicon carbide
International Journal of Machine Tools & Manufacture, 2013Co-Authors: Saurav Goel, Xichun Luo, Paul Comley, R L Reuben, Andrew CoxAbstract:Abstract In this experimental study, Diamond Turning of single crystal 6H-SiC was performed at a cutting speed of 1 m/s on an ultra-precision Diamond Turning machine (Moore Nanotech 350 UPL) to elucidate the microscopic origin of ductile-regime machining. Distilled water (pH value 7) was used as a preferred coolant during the course of machining in order to improve the tribological performance. A high magnification scanning electron microscope (SEM FIB- FEI Quanta 3D FEG) was used to examine the cutting tool before and after the machining. A surface finish of Ra=9.2 nm, better than any previously reported value on SiC was obtained. Also, tremendously high cutting resistance was offered by SiC resulting in the observation of significant wear marks on the cutting tool just after 1 km of cutting length. It was found out through a DXR Raman microscope that similar to other classical brittle materials (silicon, germanium, etc.) an occurrence of brittle-ductile transition is responsible for the ductile-regime machining of 6H-SiC. It has also been demonstrated that the structural phase transformations associated with the Diamond Turning of brittle materials which are normally considered as a prerequisite to ductile-regime machining, may not be observed during ductile-regime machining of polycrystalline materials.
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3d characterisation of tool wear whilst Diamond Turning silicon
Wear, 2007Co-Authors: Isidro Sergio Durazocardenas, Xichun Luo, Paul Shore, T Jacklin, S A Impey, Andrew CoxAbstract:Abstract Nanometrically smooth infrared silicon optics can be manufactured by the Diamond Turning process. Due to its relatively low density, silicon is an ideal optical material for weight sensitive infrared (IR) applications. However, rapid Diamond tool edge degradation and the effect on the achieved surface have prevented significant exploitation. With the aim of developing a process model to optimise the Diamond Turning of silicon optics, a series of experimental trials were devised using two ultra-precision Diamond Turning machines. Single crystal silicon specimens (1 1 1) were repeatedly machined using Diamond tools of the same specification until the onset of surface brittle fracture. Two cutting fluids were tested. The cutting forces were monitored and the wear morphology of the tool edge was studied by scanning electron microscopy (SEM). The most significant result showed the performance of one particular tool was consistently superior when compared with other Diamond tools of the same specification. This remarkable tool performance resulted in doubling the cutting distance exhibited by the other Diamond tools. Another significant result was associated with coolant type. In all cases, tool life was prolonged by as much as 300% by using a specific fluid type. Further testing led to the development of a novel method for assessing the progression of Diamond tool wear. In this technique, the Diamond tools gradual recession profile is measured by performing a series of plunging cuts. Tool shape changes used in conjunction with flank wear SEM measurements enable the calculation of the volumetric tool wear rate.
Bun Lee - One of the best experts on this subject based on the ideXlab platform.
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Machinability of Single Crystals in Diamond Turning
Materials Characterisation and Mechanism of Micro-Cutting in Ultra-Precision Diamond Turning, 2017Co-Authors: Victor Hao Wang, Bun LeeAbstract:Machinability refers to the relative ease with which a material can be cut successfully. The criteria to measure a successful cut are plentiful. Some commonly accepted measures include the surface roughness, the ease of removal of the chip, the amount of tool wear, the cutting force and the power consumption. These factors are often related to one another. This chapter showcases the material characterisation methods and the in-depth study on the machinability of single crystal materials in a series of delicate Diamond Turning experiments undertaken by the authors and their colleagues.
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Research of Surface Generation Mechanisms in Single-Point Diamond Turning
Key Engineering Materials, 2007Co-Authors: Chi Fai Cheung, Bun Lee, L.b. KongAbstract:One of the remarkable achievements of nanotechnology is the ability to achieve nanometric surface finishes in single-point Diamond Turning of high-precision components for complex optical surfaces. A better understanding of the surface generation mechanisms is of prime importance for the development for the prediction of the surface roughness. This paper presents a study of mechanisms of nano-surface generation in single-point Diamond Turning of various types of materials.
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Multi-scale modeling of surface topography in single-point Diamond Turning
Key Engineering Materials, 2007Co-Authors: Bun Lee, Chi Fai CheungAbstract:A multi-scale model is proposed to explain the effect of material induced vibration and the quantitative relation between cutting force and the surface quality from dislocations, grain orientations, cutting tools, machine tools used in the simulation of the nano-3D surface topology in single-point Diamond Turning. The model-based simulation system composes of several model elements which include a microplasticity model, a dynamic model and an enhanced surface topography model. The multi-scale model brings together knowledge from various disciplines to link up physical phenomenon occurring at different length scales to explain successfully the surface generation in single-point Diamond Turning of crystalline materials, and offers a new direction of research in ultra-precision machining.
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Anisotropy of surface roughness in Diamond Turning of brittle single crystals
Materials and Manufacturing Processes, 2002Co-Authors: Chi Fai Cheung, Bun LeeAbstract:This paper deals with an investigation of the effect of crystallographic orientation and process parameters on the surface roughness of brittle silicon single crystals in ultraprecision Diamond Turning. The process parameters involve the depth of cut, feed rate, and spindle speed. Experimental results indicate that anisotropy in surface finish occurs when the cutting direction relative to the crystal orientation varies. There exists a periodic variation of surface roughness per workpiece revolution, which is closely related to the crystallographic orientation of the crystals being cut. Such an anisotropy of surface roughness can be minimized with an appropriate selection of the feed rate, spindle speed, and depth of cut. The findings provide a means for the optimization of the surface quality in Diamond Turning of brittle silicon single crystals.
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CHARACTERISTICS OF MICROCUTTING FORCE VARIATION IN ULTRAPRECISION Diamond Turning
Materials and Manufacturing Processes, 2001Co-Authors: Bun Lee, Chi Fai CheungAbstract:An investigation of the characteristics of microcutting forces in Diamond Turning of crystalline materials is presented. The characteristics of the cutting forces were extracted and analyzed using statistical and spectrum analysis methods. A series of cutting experiments were done on a copper alloy and copper single crystals with different crystallographic orientations. Experimental results indicate that there exists a dominant frequency component and a periodicity of fluctuation of the cutting forces per workpiece revolution in the Diamond Turning of a single crystal material. The periodicity is closely related to the crystallographic orientation of the material being cut. As the depth of cut increases, the influence of crystallographic orientation of the single-crystal materials on microcutting forces is found to be more pronounced. Moreover, the cutting force ratio between the mean thrust force and the mean cutting force is found to vary with the depth of cut, and a large ratio was observed at a small ...
Chi Fai Cheung - One of the best experts on this subject based on the ideXlab platform.
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Research of Surface Generation Mechanisms in Single-Point Diamond Turning
Key Engineering Materials, 2007Co-Authors: Chi Fai Cheung, Bun Lee, L.b. KongAbstract:One of the remarkable achievements of nanotechnology is the ability to achieve nanometric surface finishes in single-point Diamond Turning of high-precision components for complex optical surfaces. A better understanding of the surface generation mechanisms is of prime importance for the development for the prediction of the surface roughness. This paper presents a study of mechanisms of nano-surface generation in single-point Diamond Turning of various types of materials.
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Multi-scale modeling of surface topography in single-point Diamond Turning
Key Engineering Materials, 2007Co-Authors: Bun Lee, Chi Fai CheungAbstract:A multi-scale model is proposed to explain the effect of material induced vibration and the quantitative relation between cutting force and the surface quality from dislocations, grain orientations, cutting tools, machine tools used in the simulation of the nano-3D surface topology in single-point Diamond Turning. The model-based simulation system composes of several model elements which include a microplasticity model, a dynamic model and an enhanced surface topography model. The multi-scale model brings together knowledge from various disciplines to link up physical phenomenon occurring at different length scales to explain successfully the surface generation in single-point Diamond Turning of crystalline materials, and offers a new direction of research in ultra-precision machining.
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Anisotropy of surface roughness in Diamond Turning of brittle single crystals
Materials and Manufacturing Processes, 2002Co-Authors: Chi Fai Cheung, Bun LeeAbstract:This paper deals with an investigation of the effect of crystallographic orientation and process parameters on the surface roughness of brittle silicon single crystals in ultraprecision Diamond Turning. The process parameters involve the depth of cut, feed rate, and spindle speed. Experimental results indicate that anisotropy in surface finish occurs when the cutting direction relative to the crystal orientation varies. There exists a periodic variation of surface roughness per workpiece revolution, which is closely related to the crystallographic orientation of the crystals being cut. Such an anisotropy of surface roughness can be minimized with an appropriate selection of the feed rate, spindle speed, and depth of cut. The findings provide a means for the optimization of the surface quality in Diamond Turning of brittle silicon single crystals.
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CHARACTERISTICS OF MICROCUTTING FORCE VARIATION IN ULTRAPRECISION Diamond Turning
Materials and Manufacturing Processes, 2001Co-Authors: Bun Lee, Chi Fai CheungAbstract:An investigation of the characteristics of microcutting forces in Diamond Turning of crystalline materials is presented. The characteristics of the cutting forces were extracted and analyzed using statistical and spectrum analysis methods. A series of cutting experiments were done on a copper alloy and copper single crystals with different crystallographic orientations. Experimental results indicate that there exists a dominant frequency component and a periodicity of fluctuation of the cutting forces per workpiece revolution in the Diamond Turning of a single crystal material. The periodicity is closely related to the crystallographic orientation of the material being cut. As the depth of cut increases, the influence of crystallographic orientation of the single-crystal materials on microcutting forces is found to be more pronounced. Moreover, the cutting force ratio between the mean thrust force and the mean cutting force is found to vary with the depth of cut, and a large ratio was observed at a small ...
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Study of Factors Affecting the Surface Quality in Ultra-Precision Diamond Turning
Materials and Manufacturing Processes, 2000Co-Authors: Chi Fai Cheung, Bun LeeAbstract:Abstract This paper deals with an investigation of the process factors and the material factors affecting the surface roughness in ultra-precision Diamond Turning. The process factors involve cutting conditions, tool geometry, and relative tool-work vibration which are related to the cutting geometry and the dynamic characteristics of the cutting process. The material factors considered are material anisotropy, swelling, and crystallographic orientation of the work materials. Experimental results indicate that the influence due to the process factors can be minimized through a proper selection of operational settings and better control of dynamic characteristics of the machine. The material factors, on the other hand, exert consistent influence on the surface roughness which can not be minimized solely by an optimization of process parameters and machine design. Based on these findings, some suggestions are proposed for the optimization of the surface quality in ultra-precision Diamond Turning.
Xichun Luo - One of the best experts on this subject based on the ideXlab platform.
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Enhancement of surface wettability via micro- and nanostructures by single point Diamond Turning
KeAi Communications Co. Ltd., 2019Co-Authors: Nicolás Cabezudo, Jining Sun, Behnam Andi, Fei Ding, Ding Wang, Wenlong Chang, Xichun LuoAbstract:Studies on surface wettability have received tremendous interest due to their potential applications in research and industrial processes. One of the strategies to tune surface wettability is modifying surface topography at micro- and nanoscales. In this research, periodic micro- and nanostructures were patterned on several polymer surfaces by ultra-precision single point Diamond Turning to investigate the relationships between surface topographies at the micro- and nanoscales and their surface wettability. This research revealed that single-point Diamond Turning could be used to enhance the wettability of a variety of polymers, including polyvinyl chloride (PVC), polyethylene 1000 (PE1000), polypropylene copolymer (PP) and polytetrafluoroethylene (PFTE), which cannot be processed by conventional semiconductor-based manufacturing processes. Materials exhibiting common wettability properties (θ ≈ 90°) changed to exhibit “superhydrophobic” behavior (θ ˃ 150°). Compared with the size of the structures, the aspect ratio of the void space between micro- and nanostructures has a strong impact on surface wettability. Keywords: Contact angle, Wettability, Single-point Diamond Turning, Structured surface, Hydrophobicit
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brittle ductile transition during Diamond Turning of single crystal silicon carbide
International Journal of Machine Tools & Manufacture, 2013Co-Authors: Saurav Goel, Xichun Luo, Paul Comley, R L Reuben, Andrew CoxAbstract:Abstract In this experimental study, Diamond Turning of single crystal 6H-SiC was performed at a cutting speed of 1 m/s on an ultra-precision Diamond Turning machine (Moore Nanotech 350 UPL) to elucidate the microscopic origin of ductile-regime machining. Distilled water (pH value 7) was used as a preferred coolant during the course of machining in order to improve the tribological performance. A high magnification scanning electron microscope (SEM FIB- FEI Quanta 3D FEG) was used to examine the cutting tool before and after the machining. A surface finish of Ra=9.2 nm, better than any previously reported value on SiC was obtained. Also, tremendously high cutting resistance was offered by SiC resulting in the observation of significant wear marks on the cutting tool just after 1 km of cutting length. It was found out through a DXR Raman microscope that similar to other classical brittle materials (silicon, germanium, etc.) an occurrence of brittle-ductile transition is responsible for the ductile-regime machining of 6H-SiC. It has also been demonstrated that the structural phase transformations associated with the Diamond Turning of brittle materials which are normally considered as a prerequisite to ductile-regime machining, may not be observed during ductile-regime machining of polycrystalline materials.
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3d characterisation of tool wear whilst Diamond Turning silicon
Wear, 2007Co-Authors: Isidro Sergio Durazocardenas, Xichun Luo, Paul Shore, T Jacklin, S A Impey, Andrew CoxAbstract:Abstract Nanometrically smooth infrared silicon optics can be manufactured by the Diamond Turning process. Due to its relatively low density, silicon is an ideal optical material for weight sensitive infrared (IR) applications. However, rapid Diamond tool edge degradation and the effect on the achieved surface have prevented significant exploitation. With the aim of developing a process model to optimise the Diamond Turning of silicon optics, a series of experimental trials were devised using two ultra-precision Diamond Turning machines. Single crystal silicon specimens (1 1 1) were repeatedly machined using Diamond tools of the same specification until the onset of surface brittle fracture. Two cutting fluids were tested. The cutting forces were monitored and the wear morphology of the tool edge was studied by scanning electron microscopy (SEM). The most significant result showed the performance of one particular tool was consistently superior when compared with other Diamond tools of the same specification. This remarkable tool performance resulted in doubling the cutting distance exhibited by the other Diamond tools. Another significant result was associated with coolant type. In all cases, tool life was prolonged by as much as 300% by using a specific fluid type. Further testing led to the development of a novel method for assessing the progression of Diamond tool wear. In this technique, the Diamond tools gradual recession profile is measured by performing a series of plunging cuts. Tool shape changes used in conjunction with flank wear SEM measurements enable the calculation of the volumetric tool wear rate.
Jiwang Yan - One of the best experts on this subject based on the ideXlab platform.
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Fabrication of Thin-Film Fresnel Optics by Combining Diamond Turning and MEMS Techniques
Procedia CIRP, 2020Co-Authors: Jiwang Yan, Kentaro Watanabe, Yutaro NakagawaAbstract:A novel fabrication process was proposed for manufacturing thin-film metal Fresnel lenses for X-ray applications, which combines MEMS technologies and Diamond Turning technology. To prevent thin-film lens substrates from deflection during Diamond Turning, the thin films were prepared on single crystalline silicon wafers by electrolytic plating. After the Fresnel lens structure has been generated on the metal thin films by Diamond Turning, the backside supporting silicon substrate was selectively removed by reactive ion etching. Experimental results demonstrated that submicron level form accuracy and nanometer level surface roughness could be achieved by the proposed hybrid fabrication process.
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Ultraprecision surface flattening of porous silicon by Diamond Turning
Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology, 2017Co-Authors: Mehdi Heidari, Jiwang YanAbstract:Abstract Porous silicon is receiving increasing interest from a wide range of scientific and technological fields due to its excellent material properties. In this study, we attempted ultraprecision surface flattening of porous silicon by Diamond Turning and investigated the fundamental material removal mechanism. Scanning electron microscopy and laser Raman spectroscopy of the machined surface showed that the mechanisms of material deformation and phase transformation around the pores were greatly different from those of bulk single-crystal silicon. The mechanism of cutting was strongly dependent on the direction of cutting with respect to pore edge orientation. Crack propagation was dominant near specific pore edges due to the release of hydrostatic pressure that was essential for ductile machining. Wax was used as an infiltrant to coat the workpiece before machining, and it was found that the wax not only prevented chips from entering the pores, but also contributed to suppress brittle fractures around the pores. The machined surface showed a nanometric surface flatness with open pores, demonstrating the possibility of fabricating high-precision porous silicon components by Diamond Turning.
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Fundamental characteristics of material removal and surface formation in Diamond Turning of porous carbon
International Journal of Additive and Subtractive Materials Manufacturing, 2017Co-Authors: Mehdi Heidari, Jiwang YanAbstract:Porous carbon is an important material for manufacturing ultraprecision air bearings. This paper investigates the material removal mechanism and surface quality of porous carbon in Diamond Turning process. A total of 32 Diamond Turning tests were performed and the effects of feed rate, depth of cut, cutting speed, and tool rake angle were investigated. Scanning electron microscopy of the machined surface showed that three types of material removal mechanisms occurred in the Diamond Turning process, which was influenced by experimental conditions. Analysis of variance of experimental data demonstrated that feed rate had the most dominant effect on surface roughness, followed by depth of cut, whereas cutting speed has little effect. Tool rake angle effects material removal behaviour in a different way from that of Diamond Turning of other brittle materials, showing that a negative rake angle is disadvantageous. The results also indicated that by controlling the machining conditions, surface roughness, core roughness and the bearing area curve of the machined surface were controllable, and there was a 25% decrease in the percentage of porosity after machining. It was demonstrated that Diamond Turning can be used as an efficient method to fabricate high-precision surfaces on porous carbon for air bearing applications.
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Fabrication of thin-film fresnel optics by combining Diamond Turning and photolithographic processes
International journal of automation technology, 2013Co-Authors: Jiwang Yan, Kenta Watanabe, Yutaro NakagawaAbstract:A novel fabrication process is proposed for manufacturing thin-film metal Fresnel lenses for X-ray applications. This process combines Diamond Turning technology and photolithographic processes. To prevent thin-film lens substrates from deflection during Diamond Turning, films were prepared on single crystalline silicon wafers by electrolytic plating. After the Fresnel lens structure is generated on the metal thin films by Diamond Turning, the silicon substrate was then removed selectively by reactive ion etching. Experimental results demonstrated that the proposed hybrid fabrication process achieves submicron form accuracy and nanometer surface roughness.
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Effect of nanoparticle lubrication in Diamond Turning of reaction-bonded SiC
International journal of automation technology, 2011Co-Authors: Jiwang Yan, Zhiyu Zhang, Tsunemoto KuriyagawaAbstract:Lubrication is a key issue in Diamond Turning of hard materials. This paper explores the feasibility of nanoparticle lubrication in Diamond Turning of reaction-bonded SiC. Four types of nanoparticles were dispersed in lubricating grease and applied to a workpiece surface. Results showed that the type and concentration of dispersed nanoparticles significantly affected lubricating performance. Grease containing 10% Cu nanoparticles produced the highest surface quality and the lowest tool wear. Lubrication is discussed in terms of nanoparticle-induced solid lubricating film formation at the tool-workpiece interface.