The Experts below are selected from a list of 2082 Experts worldwide ranked by ideXlab platform
W J Zong - One of the best experts on this subject based on the ideXlab platform.
-
Critical undeformed chip thickness of brittle materials in single point diamond turning
The International Journal of Advanced Manufacturing Technology, 2015Co-Authors: W J Zong, Z.m. Cao, Tao SunAbstract:In this work, the ultimate compression force that enables the plastic removal of brittle materials in diamond turning is initially modeled according to the theory of rigid-plastic mechanics. And subsequently, an independent oscillator model is reconstructed to calculate the microfriction force that appears at contact interface. As expected, a predictive model considering the ultimate compression force and microfriction force is finally established to calculate the critical undeformed chip thickness of brittle materials in diamond turning, in which a crack-free surface of brittle materials can be achieved as quickly as possible in a brittle-ductile coupled Cutting mode. Based on the theoretical predictions and experimental observations, the “size effect” of the critical undeformed chip thickness is discovered, i.e., that the ratio of the critical undeformed chip thickness to tool Cutting Edge Radius increases with the decrement of tool Cutting Edge Radius. Such interesting variation law is attributed to the strengthening of the effect of the microfriction and concentration of the compressive stress under a small enough Cutting Edge Radius, which produces more favorable conditions for the brittle-ductile coupled removal of brittle materials.
-
conservation law of surface roughness in single point diamond turning
International Journal of Machine Tools & Manufacture, 2014Co-Authors: W J Zong, Yanhua Huang, Y L Zhang, T SunAbstract:In this work, a comprehensive model is established to predict the surface roughness achieved by single point diamond turning. In addition to the calculation of the roughness components in relation to the kinematics and minimum undeformed chip thickness, the newly developed model also takes the effects of plastic side flow and elastic recovery of materials as machined into account. Moreover, the ‘size effect’ has also been successfully integrated into the model, i.e. an inflection point appears in the trend line of predicted surface roughness as the ratio of maximal undeformed chip thickness to Cutting Edge Radius (hDmax/rn) is equal to one unit. Face turning experiments validate that the maximal prediction error is only 13.35%. As the ratio of hDmax/rn is higher than one unit, both the prediction and experiments reveal that a conservation law exists in diamond turned surface roughness, owing to the competitive effects of kinematics, minimum undeformed chip thickness, plastic side flow and elastic recovery of materials on surface formation. Under the conservation law, the freedom control for an invariable surface roughness can be fulfilled in response to a quantitative ratio of hDmax/rn, either through an accurate configuration of feed rate and depth of cut with fixed tool nose Radius and Cutting Edge Radius, or by a reasonable selection of tool nose Radius and controlled Cutting Edge Radius with designed feed rate and depth of cut.
-
finite element optimization of diamond tool geometry and Cutting process parameters based on surface residual stresses
The International Journal of Advanced Manufacturing Technology, 2007Co-Authors: W J Zong, Kai Cheng, T Sun, Yingchun LiangAbstract:In this paper, a coupled thermo-mechanical plane-strain large-deformation orthogonal Cutting FE model is proposed on the basis of updated Lagrangian formulation to simulate diamond turning. In order to consider the effects of a diamond Cutting tool’s Edge Radius, rezoning technology is integrated into this FE based model. The flow stress of the workpiece is modeled as a function of strain, strain rate, and temperature, so as to reflect its dynamic changes in physical properties. In this way, the influences of Cutting-Edge Radius, rake angle, clearance angle, depth of cut, and Cutting velocity on the residual stresses of machined surface are analyzed by FE simulation. The simulated results indicate that a rake angle of about 10° and a clearance angle of 6° are the optimal geometry for a diamond tool to machine ductile materials. Also, the smaller the Cutting Edge Radius is, the less the residual stresses become. However, a great value can be selected for Cutting velocity. For depth of cut, the ‘size effect’ will be dependent upon it. Residual stresses will be reduced with the decrement of depth of cut, but when the depth of cut is smaller than the critical depth of cut (i.e., about 0.5 μm according to this work) residual stresses will decrease accordingly.
-
fem optimization of tool geometry based on the machined near surface s residual stresses generated in diamond turning
Journal of Materials Processing Technology, 2006Co-Authors: W J Zong, Kai Cheng, T Sun, Yingchun LiangAbstract:Abstract In this work, based on the updated Lagrangian formulation and the commercial available software, Marc2001, a coupled thermo-mechanical plane-strain large deformation orthogonal Cutting FE model is presented to simulate the diamond turning process and predict the residual stresses on the machined surface of workpiece. In order to consider the interactive influences of Cutting Edge Radius, Cutting velocity, rake angle and clearance angle on residual stresses, all simulations are programmed by an orthogonal design method, i.e. the combination design of general rotary method. As expected, two regression equations of tensile and compressive residual stresses are deduced according to the simulated results. The measured results in diamond turning show that the predicted results have a good consistency with the experimental ones. Therefore, some related analyses are carried out for the influencing factors based on the regression equations. Finally, the optimal analyses indicate that a rake angle of 15° and a clearance angle of 10° are the optimum geometry of a diamond tool in turning of ductile materials when this tool has a Cutting Edge Radius of 100–300 nm.
T Sun - One of the best experts on this subject based on the ideXlab platform.
-
conservation law of surface roughness in single point diamond turning
International Journal of Machine Tools & Manufacture, 2014Co-Authors: W J Zong, Yanhua Huang, Y L Zhang, T SunAbstract:In this work, a comprehensive model is established to predict the surface roughness achieved by single point diamond turning. In addition to the calculation of the roughness components in relation to the kinematics and minimum undeformed chip thickness, the newly developed model also takes the effects of plastic side flow and elastic recovery of materials as machined into account. Moreover, the ‘size effect’ has also been successfully integrated into the model, i.e. an inflection point appears in the trend line of predicted surface roughness as the ratio of maximal undeformed chip thickness to Cutting Edge Radius (hDmax/rn) is equal to one unit. Face turning experiments validate that the maximal prediction error is only 13.35%. As the ratio of hDmax/rn is higher than one unit, both the prediction and experiments reveal that a conservation law exists in diamond turned surface roughness, owing to the competitive effects of kinematics, minimum undeformed chip thickness, plastic side flow and elastic recovery of materials on surface formation. Under the conservation law, the freedom control for an invariable surface roughness can be fulfilled in response to a quantitative ratio of hDmax/rn, either through an accurate configuration of feed rate and depth of cut with fixed tool nose Radius and Cutting Edge Radius, or by a reasonable selection of tool nose Radius and controlled Cutting Edge Radius with designed feed rate and depth of cut.
-
finite element optimization of diamond tool geometry and Cutting process parameters based on surface residual stresses
The International Journal of Advanced Manufacturing Technology, 2007Co-Authors: W J Zong, Kai Cheng, T Sun, Yingchun LiangAbstract:In this paper, a coupled thermo-mechanical plane-strain large-deformation orthogonal Cutting FE model is proposed on the basis of updated Lagrangian formulation to simulate diamond turning. In order to consider the effects of a diamond Cutting tool’s Edge Radius, rezoning technology is integrated into this FE based model. The flow stress of the workpiece is modeled as a function of strain, strain rate, and temperature, so as to reflect its dynamic changes in physical properties. In this way, the influences of Cutting-Edge Radius, rake angle, clearance angle, depth of cut, and Cutting velocity on the residual stresses of machined surface are analyzed by FE simulation. The simulated results indicate that a rake angle of about 10° and a clearance angle of 6° are the optimal geometry for a diamond tool to machine ductile materials. Also, the smaller the Cutting Edge Radius is, the less the residual stresses become. However, a great value can be selected for Cutting velocity. For depth of cut, the ‘size effect’ will be dependent upon it. Residual stresses will be reduced with the decrement of depth of cut, but when the depth of cut is smaller than the critical depth of cut (i.e., about 0.5 μm according to this work) residual stresses will decrease accordingly.
-
fem optimization of tool geometry based on the machined near surface s residual stresses generated in diamond turning
Journal of Materials Processing Technology, 2006Co-Authors: W J Zong, Kai Cheng, T Sun, Yingchun LiangAbstract:Abstract In this work, based on the updated Lagrangian formulation and the commercial available software, Marc2001, a coupled thermo-mechanical plane-strain large deformation orthogonal Cutting FE model is presented to simulate the diamond turning process and predict the residual stresses on the machined surface of workpiece. In order to consider the interactive influences of Cutting Edge Radius, Cutting velocity, rake angle and clearance angle on residual stresses, all simulations are programmed by an orthogonal design method, i.e. the combination design of general rotary method. As expected, two regression equations of tensile and compressive residual stresses are deduced according to the simulated results. The measured results in diamond turning show that the predicted results have a good consistency with the experimental ones. Therefore, some related analyses are carried out for the influencing factors based on the regression equations. Finally, the optimal analyses indicate that a rake angle of 15° and a clearance angle of 10° are the optimum geometry of a diamond tool in turning of ductile materials when this tool has a Cutting Edge Radius of 100–300 nm.
Ni Chen - One of the best experts on this subject based on the ideXlab platform.
-
Research in minimum undeformed chip thickness and size effect in micro end-milling of potassium dihydrogen phosphate crystal
International Journal of Mechanical Sciences, 2017Co-Authors: Ni Chen, Mingjun Chen, Xudong Pei, Jun Qian, Dominiek ReynaertsAbstract:Abstract Micro-milling is a promising approach to repair the micro-defects on the surface of potassium dihydrogen phosphate (KDP) crystal. However, KDP crystal is difficult to machine due to its properties of soft-brittle and easy deliquescence. This study investigates the minimum undeformed chip thickness hm and the size effect in micro end-milling of KDP crystal by comprehensively analyzing Cutting force, specific Cutting force and machined surface quality. A model of the chip formation, which is capable of connecting the minimum undeformed chip thickness, the undeformed chip thickness and the periodicity of Cutting force together, is developed to predict the value of minimum undeformed chip thickness. The normalized minimum undeformed chip thickness λe in terms of the ratio of the minimum undeformed chip thickness to the Cutting Edge Radius re, is estimated to be 0.43 ≤ λe ≤ 0.48. The significantly non-proportional increase of specific Cutting force indicates the existence of size effects when the ratio of feed per tooth to Cutting Edge Radius ft/re is less than 0.7. The machined surface quality also reflects severe size effect by the phenomenon that the micro cracks and brittle pits appear on the groove base, and the value of surface roughness Ra is large when the ratio ft/re is less than 0.5. Furthermore, the surface quality deteriorates and the brittle Cutting appears when the ratio ft/re is much larger than 1 which seems similar to macro-milling. The perfect machined surface with almost no ploughing effect and brittle Cutting is achieved at a ratio ft/re of 0.7. Therefore, a feed per tooth, slightly larger than the minimum undeformed chip thickness but smaller than Cutting Edge Radius, is recommended for micro-milling of KDP crystal or soft-brittle crystal.
-
Cutting surface quality analysis in micro ball end milling of kdp crystal considering size effect and minimum undeformed chip thickness
Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology, 2017Co-Authors: Ni Chen, Mingjun Chen, Xudong PeiAbstract:Abstract Potassium dihydrogen phosphate (KH2PO4 or KDP) crystal is a typical soft-brittle optical crystal, and the size effect and brittle Cutting mode are easy to appear in micro ball end-milling of KDP crystal. In this paper, micro-grooving experiments are conducted to study the size effect and brittle Cutting in micro ball end-milling of KDP crystal with different feed rate and depth of cut. The Cutting force, machined groove base quality and chip morphology are collected and analyzed carefully. The size effect is discovered by the phenomena of the existence of oscillations and relaxations in Cutting force and hyper-proportional increase of specific Cutting force, when the ratio of feed per tooth to Cutting Edge Radius ft/re is less than 1. While the brittle Cutting mode is detected through the existence of sharp fluctuations in Cutting force and cracks on the groove base when the ratio ft/re is larger than 2. From the further comprehensive analysis of Cutting force, specific Cutting force, machined groove base quality and chip morphology, the Cutting parameters with ratios of the maximum undeformed chip thickness in one Cutting circle to Cutting Edge Radius hmax/re around 0.14, 0.2 and 0.4 are regarded as size effect, optimal and brittle Cutting points, respectively. The size effect, ductile Cutting and brittle Cutting zones are divided by the size effect and brittle Cutting boundaries (points). Among the optimal points, the depth of cut of 2 μm with the ratio ft/re of 1 is the optimal Cutting parameter for micro ball end-milling of KDP crystal.
-
Research in minimum undeformed chip thickness and size effect in micro end-milling of potassium dihydrogen phosphate crystal
'Elsevier BV', 2017Co-Authors: Ni Chen, Chen Mingjun, Wu Chunya, Pei Xudong, Qian Jun, Reynaerts DominiekAbstract:© 2017 Elsevier Ltd Micro-milling is a promising approach to repair the micro-defects on the surface of potassium dihydrogen phosphate (KDP) crystal. However, KDP crystal is difficult to machine due to its properties of soft-brittle and easy deliquescence. This study investigates the minimum undeformed chip thickness hm and the size effect in micro end-milling of KDP crystal by comprehensively analyzing Cutting force, specific Cutting force and machined surface quality. A model of the chip formation, which is capable of connecting the minimum undeformed chip thickness, the undeformed chip thickness and the periodicity of Cutting force together, is developed to predict the value of minimum undeformed chip thickness. The normalized minimum undeformed chip thickness λe in terms of the ratio of the minimum undeformed chip thickness to the Cutting Edge Radius re, is estimated to be 0.43 ≤ λe ≤ 0.48. The significantly non-proportional increase of specific Cutting force indicates the existence of size effects when the ratio of feed per tooth to Cutting Edge Radius ft/re is less than 0.7. The machined surface quality also reflects severe size effect by the phenomenon that the micro cracks and brittle pits appear on the groove base, and the value of surface roughness Ra is large when the ratio ft/re is less than 0.5. Furthermore, the surface quality deteriorates and the brittle Cutting appears when the ratio ft/re is much larger than 1 which seems similar to macro-milling. The perfect machined surface with almost no ploughing effect and brittle Cutting is achieved at a ratio ft/re of 0.7. Therefore, a feed per tooth, slightly larger than the minimum undeformed chip thickness but smaller than Cutting Edge Radius, is recommended for micro-milling of KDP crystal or soft-brittle crystal.status: publishe
-
the design and optimization of micro polycrystalline diamond ball end mill for repairing micro defects on the surface of kdp crystal
Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology, 2016Co-Authors: Ni Chen, Mingjun Chen, Chunya Wu, Yanan WangAbstract:Abstract Micro-milling is a promising approach to repair the micro-defects on the surface of KH2PO4 (KDP) crystal. The geometrical parameters of micro ball end mill will greatly influence the repairing process as a result of the soft brittle properties of KDP crystal. Two types of double-Edged micro ball end mills were designed and a three-dimensional finite element (FE) model was established to simulate the micro milling process of KDP crystal, which was validated by the milling experiments. The rake angle of −45°, the relief angle of 45° and the Cutting Edge Radius of 1.5–2 μm were suggested to be the optimal geometrical parameters, whereas the rake angle of −25° and the relief angle of 9° were optimal just for micro ball end mill of Type I, the configuration with the rake angles ranging from 0° to 35°, by fully considering the Cutting force, and the stress–strain distribution over the entire tool and the Cutting zone in the simulation. Moreover, the micro polycrystalline diamond (PCD) ball end mills adopting the obtained optimal parameters were fabricated by wire electro-discharge machining (WEDM) and grinding techniques, with the average surface roughness Ra of tool rake face and tool flank face ∼0.10 μm, and the Cutting Edge Radius of the tool ∼1.6 μm. The influence of tool's geometrical parameters on the finished surface quality was verified by the Cutting experiments, and the tool with symmetric structure was found to have a better Cutting performance. The repairing outlines with Ra of 31.3 nm were processed by the self-fabricated tool, which could successfully hold the growth of unstable damage sites on KDP crystal.
Kai Cheng - One of the best experts on this subject based on the ideXlab platform.
-
An innovative investigation on chip formation mechanisms in micro-milling using natural diamond and tungsten carbide tools
Journal of Manufacturing Processes, 2018Co-Authors: Zhichao Niu, Feifei Jiao, Kai ChengAbstract:Abstract This paper presents an analytical approach to investigating the chip formation process in micro-milling aluminum 6082-T6 particularly by using natural diamond and tungsten carbide tools. Through well-designed micro-milling experiments, a comparative study is conducted by utilizing a natural diamond tool with the perfectly sharpened Cutting Edge and a tungsten carbide tool with the rounded Cutting Edge respectively. Cutting forces are recorded and analyzed as one of main process indicators. The chip morphology and micro milling processes are analyzed in correlation with Cutting force variations in the processes. The size effect, minimum chip thickness and their integral effect are quantitatively assessed against the chip formation process. Research results show that the chips formed during the consecutive revolutions are affected jointly by the Cutting tool/workpiece material pair and the Cutting Edge Radius in using tungsten carbide tools; whereas the chips formed by using diamond tools are intact and separate. Furthermore, the Cutting force and thrust force are of the same order due to the Cutting Edge Radius cannot be ignored. For using a natural diamond tool with the sharp Cutting Edge, the resultant Cutting force is usually two times higher than the thrust force.
-
investigation of the size effect on burr formation in two dimensional vibration assisted micro end milling
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2011Co-Authors: H Ding, Sj Chen, Rosziati Ibrahim, Kai ChengAbstract:In precision and micro Cutting processes, the tool Cutting Edge Radius is generally quite large compared to the undeformed chip thickness, which can cause ploughing/rubbing between the tool and the workpiece and thus affect surface finish, tool wear, and burr formation. This paper investigates the effect of the size effect on top burr formation in two-dimensional vibration-assisted micro end milling (2D VAMEM). This is achieved by studying the effects of the ratio of undeformed chip thickness to the Cutting Edge Radius, and the ratio of the time when the undeformed chip thickness is less than the minimum chip thickness to the total Cutting time on top burr formation, using a model that integrates the chip thickness model of the 2D VAMEM and the minimum chip thickness prediction model. The corresponding experiments are carried out to verify the integrated model. It is found that feed per tooth has a significant effect on the height of the top burr, and the use of vibration-assisted Cutting in micro end mil...
-
finite element optimization of diamond tool geometry and Cutting process parameters based on surface residual stresses
The International Journal of Advanced Manufacturing Technology, 2007Co-Authors: W J Zong, Kai Cheng, T Sun, Yingchun LiangAbstract:In this paper, a coupled thermo-mechanical plane-strain large-deformation orthogonal Cutting FE model is proposed on the basis of updated Lagrangian formulation to simulate diamond turning. In order to consider the effects of a diamond Cutting tool’s Edge Radius, rezoning technology is integrated into this FE based model. The flow stress of the workpiece is modeled as a function of strain, strain rate, and temperature, so as to reflect its dynamic changes in physical properties. In this way, the influences of Cutting-Edge Radius, rake angle, clearance angle, depth of cut, and Cutting velocity on the residual stresses of machined surface are analyzed by FE simulation. The simulated results indicate that a rake angle of about 10° and a clearance angle of 6° are the optimal geometry for a diamond tool to machine ductile materials. Also, the smaller the Cutting Edge Radius is, the less the residual stresses become. However, a great value can be selected for Cutting velocity. For depth of cut, the ‘size effect’ will be dependent upon it. Residual stresses will be reduced with the decrement of depth of cut, but when the depth of cut is smaller than the critical depth of cut (i.e., about 0.5 μm according to this work) residual stresses will decrease accordingly.
-
fem optimization of tool geometry based on the machined near surface s residual stresses generated in diamond turning
Journal of Materials Processing Technology, 2006Co-Authors: W J Zong, Kai Cheng, T Sun, Yingchun LiangAbstract:Abstract In this work, based on the updated Lagrangian formulation and the commercial available software, Marc2001, a coupled thermo-mechanical plane-strain large deformation orthogonal Cutting FE model is presented to simulate the diamond turning process and predict the residual stresses on the machined surface of workpiece. In order to consider the interactive influences of Cutting Edge Radius, Cutting velocity, rake angle and clearance angle on residual stresses, all simulations are programmed by an orthogonal design method, i.e. the combination design of general rotary method. As expected, two regression equations of tensile and compressive residual stresses are deduced according to the simulated results. The measured results in diamond turning show that the predicted results have a good consistency with the experimental ones. Therefore, some related analyses are carried out for the influencing factors based on the regression equations. Finally, the optimal analyses indicate that a rake angle of 15° and a clearance angle of 10° are the optimum geometry of a diamond tool in turning of ductile materials when this tool has a Cutting Edge Radius of 100–300 nm.
-
The Factors Influencing on Cutting Edge Radius of Ultra-Precision Diamond Cutting Tools in Mechanical Lapping
Key Engineering Materials, 2006Co-Authors: Wen Jun Zong, Tao Sun, Kai Cheng, Yingchun LiangAbstract:A brittle-ductile transition lapping mechanism is proposed for the mechanical lapping of ultra-precision diamond Cutting tools, and then the critical depths of cut for brittle-ductile transition in different orientations and on different planes are deduced in theory. Combined the critical lapping depth with the contact accuracy between rotating scaife and lapped tool surface, the influences of processing factors on Cutting Edge Radius are studied. Both the theoretical analyses and experimental results indicate that the vibration of lapping machine tool and surface quality of scaife have enormous influences on the sharpened Cutting Edge. And lapping compression force has an optimal value. Lapping rate should be considered when lapping velocity is selected. But the smaller the lapping velocity is, the littler the Cutting Edge Radius sharpened. Finally, the optimal selections are performed for each influencing factor and a perfect diamond tool is lapped in ductile mode with a Cutting Edge Radius of 30~40nm and a surface roughness Ra of 0.7nm.
Dominiek Reynaerts - One of the best experts on this subject based on the ideXlab platform.
-
Research in minimum undeformed chip thickness and size effect in micro end-milling of potassium dihydrogen phosphate crystal
International Journal of Mechanical Sciences, 2017Co-Authors: Ni Chen, Mingjun Chen, Xudong Pei, Jun Qian, Dominiek ReynaertsAbstract:Abstract Micro-milling is a promising approach to repair the micro-defects on the surface of potassium dihydrogen phosphate (KDP) crystal. However, KDP crystal is difficult to machine due to its properties of soft-brittle and easy deliquescence. This study investigates the minimum undeformed chip thickness hm and the size effect in micro end-milling of KDP crystal by comprehensively analyzing Cutting force, specific Cutting force and machined surface quality. A model of the chip formation, which is capable of connecting the minimum undeformed chip thickness, the undeformed chip thickness and the periodicity of Cutting force together, is developed to predict the value of minimum undeformed chip thickness. The normalized minimum undeformed chip thickness λe in terms of the ratio of the minimum undeformed chip thickness to the Cutting Edge Radius re, is estimated to be 0.43 ≤ λe ≤ 0.48. The significantly non-proportional increase of specific Cutting force indicates the existence of size effects when the ratio of feed per tooth to Cutting Edge Radius ft/re is less than 0.7. The machined surface quality also reflects severe size effect by the phenomenon that the micro cracks and brittle pits appear on the groove base, and the value of surface roughness Ra is large when the ratio ft/re is less than 0.5. Furthermore, the surface quality deteriorates and the brittle Cutting appears when the ratio ft/re is much larger than 1 which seems similar to macro-milling. The perfect machined surface with almost no ploughing effect and brittle Cutting is achieved at a ratio ft/re of 0.7. Therefore, a feed per tooth, slightly larger than the minimum undeformed chip thickness but smaller than Cutting Edge Radius, is recommended for micro-milling of KDP crystal or soft-brittle crystal.
