The Experts below are selected from a list of 183 Experts worldwide ranked by ideXlab platform
Xiaodong Yang - One of the best experts on this subject based on the ideXlab platform.
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molecular dynamics simulation of material removal process and mechanism of edm using a two temperature model
Applied Surface Science, 2020Co-Authors: Xiaoming Yue, Xiaodong YangAbstract:Abstract Molecular dynamics (MD) simulation has been used to investigate the material removal mechanism in electrical Discharge machining (EDM). However, in the previous researches, the simulation model was too small, and the effect of free electrons on the heat conduction has not been considered. To solve the above two problems, in this study, a 2-D sub-micrometer scale simulation with a two-temperature model (TTM) was conducted to simulate the Discharge process of EDM, which can consider the effect of both the lattice vibration and free electrons on the heat conduction simultaneously. This 2-D sub-micrometer scale simulation model based on TTM has successfully obtained a sub-micrometer scale Discharge Crater which was close to the smallest Discharge Crater reported. Furthermore, the simulation result demonstrates that the pressure generated inside the molten pool serves as one of the removal mechanisms of molten material in the Discharge process of EDM. In addition, compared with the monocrystal copper, Discharge on the polycrystalline copper can generate much more defect structures and larger denatured layer. Moreover, the smaller the grain size of polycrystalline copper, the more the defect structures and the larger the denatured layer will be.
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Discharge Crater formation simulation coupled by thermo-fluid analysis of arc plasma in EDM
Procedia CIRP, 2020Co-Authors: Xiaodong YangAbstract:Abstract Electrical Discharge machining (EDM) is a thermal process. Thermal energy generated by a pulse Discharge between the tool electrode and workpiece results in melting and evaporation followed by material removal of both the tool electrode and workpiece, forming a Discharge Crater on electrode surfaces. In order to clarify the Crater formation process in EDM a novel simulation method was proposed in this study. As the heat source of EDM, the arc plasma directly affects the heating state of the Discharge spot, which is the most direct factor affecting the material removal. Therefore, in this study, the heat flux and the pressure distribution of the arc plasma were calculated firstly by thermo-fluid analysis. Then the simulation of Discharge Crater formation were realized by coupling the thermo-fluid analysis results of arc plasma and based on the thermo-hydraulic coupling model for the Discharge Crater. With this model not only the thermal phase transition of material caused by the high temperature is considered, the hydrodynamic characteristics of molten pool is also included. With this simulation method, the influences of Discharge parameters, such as the Discharge current, the gap distance and the Discharge duration, on the Discharge Crater were investigated.
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Simulation investigation of thermal phase transformation and residual stress in single pulse EDM of Ti–6Al–4V
Journal of Physics D, 2018Co-Authors: Jiajing Tang, Xiaodong YangAbstract:The thermal phase transformation and residual stress are ineluctable in the electrical Discharge machining (EDM) process, and they will greatly affect the working performances of the machined surface. This paper presents a simulation study on the thermal phase transformation and residual stress in single-pulse EDM of Ti–6Al–4V, which is the most popular titanium alloy in fields such as aircraft engine and some other leading industries. A multi-physics model including thermal, hydraulic, metallography and structural mechanics was developed. Based on the proposed model, the thickness and metallographic structure of the recast layer and heat affected layer (HAZ) were investigated. The distribution and characteristics of residual stress around the Discharge Crater were obtained. The recast layer and HAZ at the center of Crater are found to be the thinnest, and their thicknesses gradually increase approaching the periphery of the Crater. The recast layer undergoes a complete α' (martensitic) transformation, while the HAZ is mainly composed by the α + β + α' three-phase microstructure. Along the depth direction of Crater, the Von Mises stress increases first and then decreases, reaching its maximal value near the interface of recast layer and HAZ. In the recast layer, both compressive stress component and tensile stress component are observed. ANOVA results showed that the influence of Discharge current on maximal tensile stress is more significant than that of pulse duration, while the pulse duration has more significant influence on average thickness of the recast layer and the depth location of the maximal tensile stress. The works conducted in this study will help to evaluate the quality and integrity of EDMed surface, especially when the non-destructive testing is difficult to achieve.
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Comparison of Electrical Discharge Machining Speed of Tool Electrodes with Different Thermo-physical Properties Related to Ease of Boiling
Procedia CIRP, 2018Co-Authors: Xiaoming Yue, Xiaodong Yang, Masanori KuniedaAbstract:Abstract This paper reveals the influence of easiness of boiling of tool electrode materials on the machining speed in EDM. It is considered that during the Discharge process, both the anode and cathode emit the metal vapor jets into the gap. The interaction of the jets in the gap generates a kind of shear force acting on the molten pool, which helps remove the molten material in the workpiece. Moreover, it was found that lower boiling point of tool electrode results in stronger interaction of the jets and larger shear force, thereby the material removal volume of the Discharge Crater will be larger. To validate the above thoughts, the effect of the interaction of the jets on the material removal process was investigated through the molecular dynamics simulation. Then, the material removal volume of the Discharge Crater in a series of single Discharge experiments using tool electrodes with different thermo-physical properties related to the easiness of boiling was compared to verify the simulation results. Finally, the machining experiments were performed using a sinking EDM machine to verify the higher removal performance of tool electrode materials which are easy to emit vapor jets.
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A Thermo-hydraulic Modeling for the Formation Process of the Discharge Crater in EDM
Procedia CIRP, 2016Co-Authors: Jiajing Tang, Xiaodong YangAbstract:Abstract In EDM, the extremely high thermal power density results in melting and evaporating followed by removal electrode material, forming a Discharge Crater on electrode surfaces. Thus, during the formation process of Discharge Crater, there are the three physical forms (including solid, liquid and vapor) of electrode material and the different phase transformation between them simultaneously. In order to clarify the processes of Discharge Crater formation and material removal in electrical Discharge machining (EDM), in this paper, the thermo-hydraulic coupling numerical model of Discharge Crater formation was established and analyzed with finite element method (FEM). The model is based the theory of Multi-physics coupling related to the electrode material removal process, and the equations of heat conduction and fluid flow were coupled. In addition, the level set method was used to track the variation of the Discharge Crater surface. The simulation of the processes of Discharge Crater formation and material removal in EDM were realized. The temperature distribution, the velocity distribution and the acceleration distribution of heated zone were analyzed. It can be found that after Discharge is ignited, material removal began to occur. It was also found that the metal removal efficiency was 0.04, leaving most of the molten zone re-solidified. It can be considered that the flow flied formed in the heated zone is one of mechanisms of the material removal and the forming of the Discharge Crater.
Masanori Kunieda - One of the best experts on this subject based on the ideXlab platform.
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influences of Discharge current pulse shape on machining characteristics in edm
Procedia CIRP, 2020Co-Authors: Mayu Shinohara, Masanori KuniedaAbstract:Abstract It is known that only several percent of the meltpool in the Discharge Crater is removed as debris in electrical Discharge machining (EDM). Hence, machining rate would be improved and thickness of the damaged layer would be decreased if most of the molten material could be removed. In the previous researches, it was found that the removal volume of single pulse Discharge, machining rate of continuous pulse Discharges, and tool wear are significantly influenced by the rising and falling speeds of the Discharge current pulse. In the previous researches however, the influences of the pulse shapes were investigated under a limited machining condition. Machining characteristics of these pulse shapes have not been compared under different machining conditions. This study shows that the most efficient pulse shape can be different if the Discharge duration and Discharge current are changed. The reason why the optimum pulse shape depends on the machining conditions is discussed.
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Comparison of Electrical Discharge Machining Speed of Tool Electrodes with Different Thermo-physical Properties Related to Ease of Boiling
Procedia CIRP, 2018Co-Authors: Xiaoming Yue, Xiaodong Yang, Masanori KuniedaAbstract:Abstract This paper reveals the influence of easiness of boiling of tool electrode materials on the machining speed in EDM. It is considered that during the Discharge process, both the anode and cathode emit the metal vapor jets into the gap. The interaction of the jets in the gap generates a kind of shear force acting on the molten pool, which helps remove the molten material in the workpiece. Moreover, it was found that lower boiling point of tool electrode results in stronger interaction of the jets and larger shear force, thereby the material removal volume of the Discharge Crater will be larger. To validate the above thoughts, the effect of the interaction of the jets on the material removal process was investigated through the molecular dynamics simulation. Then, the material removal volume of the Discharge Crater in a series of single Discharge experiments using tool electrodes with different thermo-physical properties related to the easiness of boiling was compared to verify the simulation results. Finally, the machining experiments were performed using a sinking EDM machine to verify the higher removal performance of tool electrode materials which are easy to emit vapor jets.
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Analysis of Micro Fin Deformation Due to Micro EDM
Procedia CIRP, 2016Co-Authors: Mohd Zahiruddin, Masanori KuniedaAbstract:Abstract This work describes deformation of fin machined by micro electrical Discharge machining (EDM). First, temperature distribution in a workpiece due to micro EDM single Discharge was calculated using finite element method, and the result was used to calculate residual stress. It was found that the residual stress in the radial direction, σ r ( z ) along the centre axis of the single Discharge Crater was distributed non-linearly in thickness direction from top surface of the workpiece. Then, in structural analysis, the result of σ r ( z ) was imposed within micro fin model. Here, thermal stress field due to series of sequential Discharges was considered. The summation of calculated deflections after three sequential Discharges was almost equal to the measurement result. To explain the deformation of fin, additional models of uniform rectangular beam were built. As a result, the non-linear distribution of σ r ( z ) was found to be the main reason that causes the non-uniform curvature of micro fin.
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molecular dynamics simulation of pressure generated inside melting area in edm
Key Engineering Materials, 2014Co-Authors: Xiaodong Yang, Xiao Han, Masanori KuniedaAbstract:Electrical Discharge phenomena in EDM occur in a very short time period and in a very narrow space, thus making both observation and theoretical analysis extremely difficult. For this reason, the material removal mechanism in EDM has yet to be understood clearly. EDM is a thermal process. Thermal energy is generated by a pulse Discharge between the workpiece and the tool electrode. It results in melting and evaporating followed by removal of both the workpiece and tool electrode, forming a Discharge Crater on both surfaces. In this paper, the hydrostatic pressure distribution in melting area was simulated by Molecular Dynamics (MD) methods. The analysis shows that after Discharge is ignited, extremely high pressure is generated inside the melting area. The pressure distribution along the central axis of the melting area at different times indicates that during the Discharge duration, the hydrostatic pressure quickly increases to a peak value along the depth direction of melting area and then reduced to 0 GPa in the unaffected area. It was also found that with the passage of time, the depth of the point where the pressure peaks increases with the formation of the Discharge Crater, accompanied by the decrease in the peak pressure. In addition, the ejected material atoms at different times during the removal process were also analyzed. It was found that the material ablation occurs mostly during the Discharge duration.
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Clarification of EDM gap phenomena using transparent electrodes
CIRP Annals, 2014Co-Authors: Tomoo Kitamura, Masanori KuniedaAbstract:Abstract This paper describes the heat source diameter of single pulse Discharge in electrical Discharge machining. To observe the Discharge plasma, SiC and Ga 2 O 3 single crystals were used as the electrode material since they are optically transparent and electrically conductive. It was found that plasma diameter expands within a few microseconds after dielectric breakdown and the plasma diameter is much larger than the Discharge Crater. From the measured diameter of the Crater, the heat source diameter was obtained by solving the inverse problem of heat conduction analysis, and it was found that the heat source diameter is smaller than the plasma diameter but larger than the Crater diameter.
Dong-yea Sheu - One of the best experts on this subject based on the ideXlab platform.
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Micro-spherical probes machining by EDM
Journal of Micromechanics and Microengineering, 2004Co-Authors: Dong-yea SheuAbstract:This paper describes a new hybrid micro-machining method, which combines wire electro Discharge grinding technology with one pulse electro Discharge, to fabricate micro-spherical probes and micro-spherical cavities. The results show that a burnished micro-spherical probe with about 40 µm diameter could be formed instantaneously with the hybrid machining process, which is not available in the conventional micro-machining method. The deviation in diameter and roundness tolerances of micro-spherical probes is about 1 µm and 3 µm, respectively. Compared with conventional electro Discharge machining, the surface roughness of the spherical probe is much smaller than a Discharge Crater. It will be possible to achieve more accurate three-dimensional measurements with the micro-spherical probe attached to the coordinate measuring machine in the future.
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Multi-spherical probe machining by EDM: Combining WEDG technology with one-pulse electro-Discharge
Journal of Materials Processing Technology, 2004Co-Authors: Dong-yea SheuAbstract:Abstract This paper describes a new hybrid technique combining wire electro-Discharge grinding (WEDG) technology with one-pulse electro-Discharge (OPED), to fabricate multi-micro-spherical probes. The results show that a burnished micro-spherical probe with diameter of about 40 μm could be formed instantaneously, which is not available with conventional machining methods. The unevenness of the radius is about 3 μm with repeatedly machining at the same conditions and the center shifting tolerances of the sphere is about 1 μm. Compared with micro-Discharge electro-machining (EDM), the surface roughness of the probe is much smaller than Discharge Crater.
Wansheng Zhao - One of the best experts on this subject based on the ideXlab platform.
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simulation of temperature distribution and Discharge Crater of sicp al composites in a single pulsed arc Discharge
Chinese Journal of Aeronautics, 2020Co-Authors: Wansheng Zhao, Ji-peng Chen, G U Lin, Mario GuaglianoAbstract:Abstract SiCp/Al composites are difficult-to-cut materials. In recent years, electrical arc Discharge machining has been developed to improve the machinability of these materials. However, there is a big challenge to build a satisfactory heat transfer model of SiCp/Al composites in the arc machining. This is not only because of the material property difference between the reinforcement and matrix material but also because of the micro-dimension SiC reinforcements. This paper established a new heat conduction simulation model considering the SiC particle-Al matrix interface and the phase change effects in a single-pulsed arc Discharge of SiCp/Al composites. A novel SiC particle-Al matrix cell geometric model was designed firstly. Then, the temperature distribution at a different depth from the workpiece surface was analyzed, the influence of sic volume fraction on temperature field was studied, and the contribution of the interface thermal resistance and latent heat were explained. To demonstrate the validity of the new numerical model, comparisons and verifications were employed. Finally, the method of improving the model was proposed and the machining mechanism of arc Discharge of SiCp/Al matrix materials was discussed. It was found that high temperature is prone to concentrate on the surface layers of the workpiece especially when the SiC fraction is high, also, the temperature fluctuates respectively at the evaporation point of aluminum and SiC, and the SiC-Al resistance has less influence on temperature distribution compared to latent heat, etc. The model build in this work improves the simulation accuracy observably compared to the previous model, and the simulation work will help to acquire a detailed mechanism of material removal of SiCp/Al composites in the arc Discharge machining.
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Simulation of temperature distribution and Discharge Crater of SiCp/Al composites in a single-pulsed arc Discharge
Chinese Journal of Aeronautics, 2020Co-Authors: Ji-peng Chen, Wansheng Zhao, Mario GuaglianoAbstract:Abstract SiCp/Al composites are difficult-to-cut materials. In recent years, electrical arc Discharge machining has been developed to improve the machinability of these materials. However, there is a big challenge to build a satisfactory heat transfer model of SiCp/Al composites in the arc machining. This is not only because of the material property difference between the reinforcement and matrix material but also because of the micro-dimension SiC reinforcements. This paper established a new heat conduction simulation model considering the SiC particle-Al matrix interface and the phase change effects in a single-pulsed arc Discharge of SiCp/Al composites. A novel SiC particle-Al matrix cell geometric model was designed firstly. Then, the temperature distribution at a different depth from the workpiece surface was analyzed, the influence of sic volume fraction on temperature field was studied, and the contribution of the interface thermal resistance and latent heat were explained. To demonstrate the validity of the new numerical model, comparisons and verifications were employed. Finally, the method of improving the model was proposed and the machining mechanism of arc Discharge of SiCp/Al matrix materials was discussed. It was found that high temperature is prone to concentrate on the surface layers of the workpiece especially when the SiC fraction is high, also, the temperature fluctuates respectively at the evaporation point of aluminum and SiC, and the SiC-Al resistance has less influence on temperature distribution compared to latent heat, etc. The model build in this work improves the simulation accuracy observably compared to the previous model, and the simulation work will help to acquire a detailed mechanism of material removal of SiCp/Al composites in the arc Discharge machining.
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Research on the Plasma Channel Expansion Behavior of Cathode in Electrical Arc Machining
Procedia CIRP, 2020Co-Authors: Xiaoming Kang, Wansheng ZhaoAbstract:Abstract As a thermal erosion process, the performance of electrical arc machining (EAM)—including material removal rate (MRR) and tool wear ratio (TWR)—is greatly influenced by arc plasma in the gap between the workpiece and the electrode. Therefore, it is necessary to study plasma channel expansion behaviour (PCEB) to disclose the EAM mechanism. By far, negative polarity EAM is usually adopted to achieve a higher MRR; most current research concentrates on the PCEB of the anode side for it directly relates to the MRR. However, in electrical machining, the plasma ignites from the cathode side, and positive polarity EAM is also recommended to improve the surface quality. Thus, the PCEB of the cathode is also very important. In this paper, a set of single Discharge observation experiments was implemented to investigate the PCEB at cathode side by utilizing a four-frame high-speed camera. Based on time solved imaging of single Discharge, the relationship between the PCEB and primary electrical parameters, including Discharge time and peak current, was studied. Besides, the PCEBs of three conventional electrode materials were compared to find the mutual relationship between the material properties and expansion behaviour. The PCEB formulations of these materials under the specific parameters were further deduced and applied to simulate the single Discharge Crater. Finally, to elaborate the validity of the formulations, the simulation results above were compared with the results obtained by using uniform plasma diameter.
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Coupled numerical simulation of arc plasma channel evolution and Discharge Crater formation in arc Discharge machining
International Journal of Heat and Mass Transfer, 2019Co-Authors: Yingmou Zhu, Ahmad Farhadi, Wansheng ZhaoAbstract:Abstract A coupled electrode-plasma-workpiece mathematical model was proposed to study the development of arc plasma channels and the formation of Discharge Craters. In order to avoid deviations caused by heat source empirical equations and discrepancies in energy distribution type, a reliable simulation based on equilibrium Discharge conditions was utilized to reveal the arc discharging process. To better describe this coupled model, the basic theoretical analysis of arc discharging was first introduced, after which the multi-field coupling and governing equations of arc discharging model were studied. Based on the simulation results, researchers investigated the heat transferred from the arc plasma channel to the workpiece and electrode and obtained the arc plasma shape. The Discharge Crater on the workpiece and the electrode erosion process were also analyzed. Additionally, a single arc discharging experiment was conducted in order to verify the simulation results. The experiment results reflect that the arc plasma shape and Discharge Crater morphology fits with the simulation results. The comparison indicates that the coupled electrode-plasma-workpiece model was effective in analyzing the arc discharging process.
Ji-peng Chen - One of the best experts on this subject based on the ideXlab platform.
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simulation of temperature distribution and Discharge Crater of sicp al composites in a single pulsed arc Discharge
Chinese Journal of Aeronautics, 2020Co-Authors: Wansheng Zhao, Ji-peng Chen, G U Lin, Mario GuaglianoAbstract:Abstract SiCp/Al composites are difficult-to-cut materials. In recent years, electrical arc Discharge machining has been developed to improve the machinability of these materials. However, there is a big challenge to build a satisfactory heat transfer model of SiCp/Al composites in the arc machining. This is not only because of the material property difference between the reinforcement and matrix material but also because of the micro-dimension SiC reinforcements. This paper established a new heat conduction simulation model considering the SiC particle-Al matrix interface and the phase change effects in a single-pulsed arc Discharge of SiCp/Al composites. A novel SiC particle-Al matrix cell geometric model was designed firstly. Then, the temperature distribution at a different depth from the workpiece surface was analyzed, the influence of sic volume fraction on temperature field was studied, and the contribution of the interface thermal resistance and latent heat were explained. To demonstrate the validity of the new numerical model, comparisons and verifications were employed. Finally, the method of improving the model was proposed and the machining mechanism of arc Discharge of SiCp/Al matrix materials was discussed. It was found that high temperature is prone to concentrate on the surface layers of the workpiece especially when the SiC fraction is high, also, the temperature fluctuates respectively at the evaporation point of aluminum and SiC, and the SiC-Al resistance has less influence on temperature distribution compared to latent heat, etc. The model build in this work improves the simulation accuracy observably compared to the previous model, and the simulation work will help to acquire a detailed mechanism of material removal of SiCp/Al composites in the arc Discharge machining.
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Simulation of temperature distribution and Discharge Crater of SiCp/Al composites in a single-pulsed arc Discharge
Chinese Journal of Aeronautics, 2020Co-Authors: Ji-peng Chen, Wansheng Zhao, Mario GuaglianoAbstract:Abstract SiCp/Al composites are difficult-to-cut materials. In recent years, electrical arc Discharge machining has been developed to improve the machinability of these materials. However, there is a big challenge to build a satisfactory heat transfer model of SiCp/Al composites in the arc machining. This is not only because of the material property difference between the reinforcement and matrix material but also because of the micro-dimension SiC reinforcements. This paper established a new heat conduction simulation model considering the SiC particle-Al matrix interface and the phase change effects in a single-pulsed arc Discharge of SiCp/Al composites. A novel SiC particle-Al matrix cell geometric model was designed firstly. Then, the temperature distribution at a different depth from the workpiece surface was analyzed, the influence of sic volume fraction on temperature field was studied, and the contribution of the interface thermal resistance and latent heat were explained. To demonstrate the validity of the new numerical model, comparisons and verifications were employed. Finally, the method of improving the model was proposed and the machining mechanism of arc Discharge of SiCp/Al matrix materials was discussed. It was found that high temperature is prone to concentrate on the surface layers of the workpiece especially when the SiC fraction is high, also, the temperature fluctuates respectively at the evaporation point of aluminum and SiC, and the SiC-Al resistance has less influence on temperature distribution compared to latent heat, etc. The model build in this work improves the simulation accuracy observably compared to the previous model, and the simulation work will help to acquire a detailed mechanism of material removal of SiCp/Al composites in the arc Discharge machining.