In order to investigate the effects of pockets in the porthole die on the metal flow,temperature at the die bearing exit and the extrusion load were contrasted with the traditional die design without the pockets in th...In order to investigate the effects of pockets in the porthole die on the metal flow,temperature at the die bearing exit and the extrusion load were contrasted with the traditional die design without the pockets in the lower die.Two different multi-hole porthole dies with and without pockets in lower die were designed.And the extrusion process was simulated based on the commercial software DEFORM-3D.The simulation results show that the pockets could be used to effectively adjust the metal flow and especially benefit to the metal flow under the legs.In addition,the maximum temperature at the die bearing and the peak extrusion load decrease,which indicates the possibility of increasing the extrusion speed and productivity.展开更多
The effects of die structure such as the height of the welding,the welding angle and chamber the shape of the bridge on the welding quality of profiles were investigated by means of the commercial software DEFORM-3D.T...The effects of die structure such as the height of the welding,the welding angle and chamber the shape of the bridge on the welding quality of profiles were investigated by means of the commercial software DEFORM-3D.The numerical simulation results show that the welding quality of the hollow profiles has great sensitive to the die structure.With increasing the welding chamber height and decreasing the welding angle of the die leg can improve the welding quality.In addition,the welding quality index k of the new designed shape of the die leg is little down from 4.1 to 3.9 comparing the standard leg.展开更多
To optimize milling force and machining accuracy quality in corner milling process, the changing law of milling force is revealed by Finite Element Method（FEM）. Based on DEFORM software a serial of 3D FEM models for...To optimize milling force and machining accuracy quality in corner milling process, the changing law of milling force is revealed by Finite Element Method（FEM）. Based on DEFORM software a serial of 3D FEM models for corner milling process are devloped. Tool curved trajectory is achieved by establishing accurate relationship of tool location with milling time. Adaptive remeshing technique and iterative algorithm are adopted to ensure convergence of FEM model. Component force characteristics are revealed by analyzing FEM simulation results. It indicates that the milling force in Y direction becomes negative comparing with forces in X and Z direction. Magnitude of forces in three directions decreases with increase of spindle speed, while it increases with increase of milling feedrate. The simulation results for cutting force are in good agreement with those obtained from experiment. The FEM simulation model is first successfully established for corner milling process in this study, and the results provide a guide for optimizing cutting parameters in cutting process.展开更多
Both experiment and simulation are made on the AlMg4 . 5Mn0 .4 sheet blanking with 1 % , 10% and 20% relative clearance respectively. The cutting force curves and the cutting surface parameters which can be used to de...Both experiment and simulation are made on the AlMg4 . 5Mn0 .4 sheet blanking with 1 % , 10% and 20% relative clearance respectively. The cutting force curves and the cutting surface parameters which can be used to describe the quality of the blankings are measured. Simulation is accomplished by MARC Autoforge software package. Calculated cutting forces are always bigger than measured ones. All difference between experiment and simulation is not greater than 20% . It is feasible making virtual experiment on workstation to estimate the cutting force and to predict the quality of the workpiece for new material using certain blanking technical parameters.展开更多
The application of advanced high strength steel （AHSS） has an important significance in the development of the lightweight of automobile, but the parts made of AHSS usually have defects, such as fracture and large a...The application of advanced high strength steel （AHSS） has an important significance in the development of the lightweight of automobile, but the parts made of AHSS usually have defects, such as fracture and large amount of springback, etc. In this paper, a model of multi-pass roll form- ing and springback process of AHSS is established with finite element software ABAQUS. Then a roll forming experiment is performed, and simulation and experimental results have been compared and analyzed. The model is established under complex contact conditions, including self-contact condi- tion. The results shows that during the process of sheet bending, large Mises stresses appear at ben- ding corners. The smaller the bending radius is, the larger the Mises stress and strain are. Thick- ness of sheet metal changes exceeds a certain limit, the differently if the bending radius is different. When the bending radius change tendency of the sheet thickness turns from increase to decrease.展开更多
Some techniques such as die surface description, contact judgement algorithm and remeshing are proposed to improve the robustness of the numerical solution. Based on these techniques, a three-dimensional rigid-plastic...Some techniques such as die surface description, contact judgement algorithm and remeshing are proposed to improve the robustness of the numerical solution. Based on these techniques, a three-dimensional rigid-plastic FEM code has been developed. Isothermal forging process of a cylindrical housing has been simulated. The simulation results show that the given techniques and the FEM code are reasonable and feasible for three-dimensional bulk forming processes.展开更多
The precision forging process is simulated by commercial software Deform 3D using a rigid visco-plastic model to predict the status of metal flow and the distribution of equivalent plastic strain, providing guidance f...The precision forging process is simulated by commercial software Deform 3D using a rigid visco-plastic model to predict the status of metal flow and the distribution of equivalent plastic strain, providing guidance for making decision on the optimal choice of process parameters and mould structure. Trial forging was used to verify the effectiveness of FEM simulation results.展开更多
Laser forming involves heating sheet metal workpiece along a certain path with adefocused laser beam directed irradiate to the surface. During laser forming, a tran-sient temperature fields is caused by the irradiatio...Laser forming involves heating sheet metal workpiece along a certain path with adefocused laser beam directed irradiate to the surface. During laser forming, a tran-sient temperature fields is caused by the irradiation and travelling of a laser beam.Consequently, thermal expansion and contraction take place, and allows the thermal-mechanical forming of complex shapes. This is a new manufacturing technique thatforming metal sheet only by thermal stress. Therefore, the analysis of temperaturefields and stress fields are very useful for studying the forming mechanism and con-trolling the accuracy of laser forming. The non--liner finite element solver, MARC, isemployed to solve the thermal--mechanical analysis. Using this model, the stress andstrain distribution of pure aluminum plate with different thickness are analyzed. Theinfluence of scanning speed on temperature fields and plastic strain of metal sheet un-der the condition of constant line energy are also presented. Numerical results agreewell with the experimental results.展开更多
The coupling mechanism in freezing process of seepage ground was studied and a simplified coupling math model was proposed. The nonlinear and coupling problems of PDEs were well solved using the exponential function, ...The coupling mechanism in freezing process of seepage ground was studied and a simplified coupling math model was proposed. The nonlinear and coupling problems of PDEs were well solved using the exponential function, error function and normal distribution function, and a series of FEM equations of coupled fields of temperature and seepage were deduced and put forward. With the example of shaft ground freezing, the formation of freezing wall in seepage ground was simulated.展开更多
Induction heating has been widely used by the heat treatment industry mainly in the wind-power and automotive sectors,in particular for hardening purposes,in a broad range of applications,its main advantages being the...Induction heating has been widely used by the heat treatment industry mainly in the wind-power and automotive sectors,in particular for hardening purposes,in a broad range of applications,its main advantages being the high repeatability and easy automation of the process,both factors leading to improved manufacturing efficiency and reduced CO;emissions.Though,traditional furnace-based case hardening treatments still represent the choice of reference when performance requirements are particularly demanding,either for the critical operating conditions or safety-related issues.The processes of CIH（Contour Induction Hardening）,compared to the traditional carburizing processes,allows to reduce the deformations after heat treatment.The main purpose of these treatments,as well as increases the surface hardness of the piece,is to induce compressive stresses in the superficial layer,improving the fatigue behavior.A multiphysics magneto-thermal simulation can be developed in order to calculate the temperature distribution in the gear,setting the input parameters such as currents,frequencies and treatment times.展开更多
The modeling and identification of anisotropic damping property of Ni based single crystal alloys are presented. The anisotropic material damping property is modeled by 3 D rheological equations and identified by us...The modeling and identification of anisotropic damping property of Ni based single crystal alloys are presented. The anisotropic material damping property is modeled by 3 D rheological equations and identified by using specimen modal damping ratios and FEM simulation. The measured damping ratios which exhibit strong anisotropy are predicted better by the method presented than by other methods.展开更多
In this paper the soft medium tube expanding process of different loading case and tube sheet structure is simulated with FEM. The expanding patterns under different conditions are obtained. The correction of the Sing...In this paper the soft medium tube expanding process of different loading case and tube sheet structure is simulated with FEM. The expanding patterns under different conditions are obtained. The correction of the Single-tube Model is verified, and cor- responding procedures are also proposed to correct the error.展开更多
Fracture prediction is a technical issue in the field of petroleum exploration and production worldwide.Although there are many approaches to predict the distribution of cracks underground,these approaches have some l...Fracture prediction is a technical issue in the field of petroleum exploration and production worldwide.Although there are many approaches to predict the distribution of cracks underground,these approaches have some limitations.To resolve these issues,we ascertained the relation between numerical simulations of tectonic stress and the predicted distribution of fractures from the perspective of geologic genesis,based on the characteristics of the shale reservoir in the Longmaxi Formation in Dingshan;the features of fracture development in this reservoir were considered.3 D finite element method(FEM)was applied in combination with rock mechanical parameters derived from the acoustic emissions.The paleotectonic stress field of the crack formation period was simulated for the Longmaxi Formation in the Dingshan area.The splitting factor in the study area was calculated based on the rock breaking criterion.The coefficient of fracture development was selected as the quantitative prediction classification criteria for the cracks.The results show that a higher coefficient of fracture development indicates a greater degree of fracture development.On the basis of the fracture development coefficient classification,a favorable area was identified for the development of fracture prediction in the study area.The prediction results indicate that the south of the Dingshan area and the DY3 well of the central region are favorable zones for fracture development.展开更多
Chatter vibration is a major obstacle inachieveing increased machining performance. In thisresearch, a finite element model of chip formation in a 2Dmilling process is used to predict the occurrence of chattervibratio...Chatter vibration is a major obstacle inachieveing increased machining performance. In thisresearch, a finite element model of chip formation in a 2Dmilling process is used to predict the occurrence of chattervibrations, and to investigate the effects of variousmachining parameters on this phenomenon. The dynamicproperties of the machine tool at the tool tip are obtainedbased on experimental modal analysis, and are used in themodel as the cutter dynamics. The model allows for thenatural development of vibration as the result of the chip-tool engagement, and accounts for various phenomena thatoccur at the chip-tool interface ultimately leading tostable or unstable cutting. The model was used todemonstrate the effects of the machining parameters, suchas the axial depth of cut, radial immersion, and feed rate,on the occurrence of chatter. Additionally, the phenomenonof jumping out of the cut region could be observed in thismodel and its effect on the chatter process is demonstrated.The numerical model is verified based on comparisons withexperimental results.展开更多
True stress?true strain curves of Incoloy028alloy at high temperature and strain rate were investigated by hot compression test.These curves show that the maximum flow stress decreases with the increase in temperature...True stress?true strain curves of Incoloy028alloy at high temperature and strain rate were investigated by hot compression test.These curves show that the maximum flow stress decreases with the increase in temperature and the decrease in strain rate.FEM simulation was employed to investigate the influence of temperature,extrusion speed and friction coefficient on the extrusion load,stress,strain and strain rate in the extrusion process.The increase of extrusion temperature results in decrease of load and deformation resistance,but has little influence on strain and strain rate.When extrusion speed changes between200and350mm/s,no obvious change about extrusion load can be found.Sharp peak value up to42500kN emerges in the extrusion load curve and the extrusion process becomes unstable seriously when extrusion speed rises up to400mm/s.Both stress and strain rate increase with the raise of extrusion speed.When friction coefficient is between0.02and0.03,deformation resistance is about160MPa and the strain rate can be limited below70s?1.Successful production of Incoloy028tube verifies the optimized parameters by FEM simulation analysis,and mechanical tests results of the products meet the required properties.展开更多
The samples obtained by Finite Element Method (FEM) simulation for section extrusion process have been trained on BP Neural Networks. The mapping relationsbetween die's geometrical parameters and energetic paramet...The samples obtained by Finite Element Method (FEM) simulation for section extrusion process have been trained on BP Neural Networks. The mapping relationsbetween die's geometrical parameters and energetic parameters, such as stress and strain generated in the die are established. The extrusion process model and its expert system are also determined. The excellent expansibility this system possesses provides a new prospect for the future development of expert system for section extrusion dies.展开更多
Finite element simulations are carried out to examine the mechanical behavior of the metallic hollow sphere （MHS） material during their large plastic deformation and to estimate the energy absorbing capacity of thes...Finite element simulations are carried out to examine the mechanical behavior of the metallic hollow sphere （MHS） material during their large plastic deformation and to estimate the energy absorbing capacity of these materials under uniaxial compression. A simplified model is proposed from experimental observations to describe the connection between the neighboring spheres, which greatly improves the computation efficiency. The effects of the governing physical and geometrical parameters are evaluated; whilst a special attention is paid to the plateau stress, which is directly related to the energy absorbing capacity. Finally, the empirical functions of the relative material density are proposed for the elastic modulus, yield strength and plateau stress for FCC packing arrangement of hollow spheres, showing a good agreement with the experimental results obtained in our previous study.展开更多
In the hot forming of Mn18Cr18N steel, such problems as easy cracking, difficult controlling of forming paramenters often occur. In this paper,the variation rule of the plasticity of the steel, the starting mechanis...In the hot forming of Mn18Cr18N steel, such problems as easy cracking, difficult controlling of forming paramenters often occur. In this paper,the variation rule of the plasticity of the steel, the starting mechanism of micro-crack and its generating characteristics were studied with the combination of thermodynamic simulation test, micro-simulation and FEM, the related data of microstructure change and hot forming parameters were produced. The hot forming process of 600MW generator retaining ring was analyzed as an example.展开更多
The high temperature split Hopkinson pressure bar （SHPB） compression experiment is conducted to obtain the data relationship among strain, strain rate and flow stress from room temperature to 550 C for aeronautical ...The high temperature split Hopkinson pressure bar （SHPB） compression experiment is conducted to obtain the data relationship among strain, strain rate and flow stress from room temperature to 550 C for aeronautical aluminum alloy 7050-T7451. Combined high-speed orthogonal cutting experiments with the cutting process simulations, the data relationship of high temperature, high strain rate and large strain in high-speed cutting is modified. The Johnson-Cook empirical model considering the effects of strain hardening, strain rate hardening and thermal softening is selected to describe the data relationship in high-speed cutting, and the material constants of flow stress constitutive model for aluminum alloy 7050-T7451 are determined. Finally, the constitutive model of aluminum alloy 7050-T7451 is established through experiment and simulation verification in high-speed cutting. The model is proved to be reasonable by matching the measured values of the cutting force with the estimated results from FEM simulations.展开更多
The hot deformation behavior of Ti-6 Al-4 V-0.1 Ru titanium alloy was investigated by isothermal compression tests on a Gleeble-3500 thermal simulator over deformation temperature range of 1023-1423 K and strain rate ...The hot deformation behavior of Ti-6 Al-4 V-0.1 Ru titanium alloy was investigated by isothermal compression tests on a Gleeble-3500 thermal simulator over deformation temperature range of 1023-1423 K and strain rate of 0.01-10 s-1.Arrhenius-type constitutive models were developed for temperature ranges of bothα+βdual phase andβsingle phase at strain of 0.1.Afterwards,a series of material constants(including activation energy Q,material constants n,αand ln A)as polynomial functions of strain were introduced into Arrhenius-type models.Finally,the improved Arrhenius-type models in temperature field ofα+βandβphase were constructed.The results show that the improved Arrhenius-type models contribute to the calculation of Zener-Hollomon(Z)parameter,and the microstructural evolution mechanism is uncovered by combining microstructure observations with Z-parameter.Furthermore,the improved Arrhenius-type models are also helpful to improve the accuracy of finite element method(FEM)simulation in the deformation process of Ti-6 Al-4 V-0.1 Ru titanium alloy.展开更多
基金Project(2007BAE38B00) supported by the National Key Technology R&D Program in the 11th Five Year Plan of China
文摘In order to investigate the effects of pockets in the porthole die on the metal flow,temperature at the die bearing exit and the extrusion load were contrasted with the traditional die design without the pockets in the lower die.Two different multi-hole porthole dies with and without pockets in lower die were designed.And the extrusion process was simulated based on the commercial software DEFORM-3D.The simulation results show that the pockets could be used to effectively adjust the metal flow and especially benefit to the metal flow under the legs.In addition,the maximum temperature at the die bearing and the peak extrusion load decrease,which indicates the possibility of increasing the extrusion speed and productivity.
基金Founded by the National Key Technology R&D Program in the 11th Five Year Plan of China(2007BAE38B00)
文摘The effects of die structure such as the height of the welding,the welding angle and chamber the shape of the bridge on the welding quality of profiles were investigated by means of the commercial software DEFORM-3D.The numerical simulation results show that the welding quality of the hollow profiles has great sensitive to the die structure.With increasing the welding chamber height and decreasing the welding angle of the die leg can improve the welding quality.In addition,the welding quality index k of the new designed shape of the die leg is little down from 4.1 to 3.9 comparing the standard leg.
基金Supported by National Natural Science Foundation of China(Grant Nos.51575147,51235003)Science Funds for the Young Innovative Talents of Harbin University of Science and Technology,China(Grant No.201507)
文摘To optimize milling force and machining accuracy quality in corner milling process, the changing law of milling force is revealed by Finite Element Method（FEM）. Based on DEFORM software a serial of 3D FEM models for corner milling process are devloped. Tool curved trajectory is achieved by establishing accurate relationship of tool location with milling time. Adaptive remeshing technique and iterative algorithm are adopted to ensure convergence of FEM model. Component force characteristics are revealed by analyzing FEM simulation results. It indicates that the milling force in Y direction becomes negative comparing with forces in X and Z direction. Magnitude of forces in three directions decreases with increase of spindle speed, while it increases with increase of milling feedrate. The simulation results for cutting force are in good agreement with those obtained from experiment. The FEM simulation model is first successfully established for corner milling process in this study, and the results provide a guide for optimizing cutting parameters in cutting process.
文摘Both experiment and simulation are made on the AlMg4 . 5Mn0 .4 sheet blanking with 1 % , 10% and 20% relative clearance respectively. The cutting force curves and the cutting surface parameters which can be used to describe the quality of the blankings are measured. Simulation is accomplished by MARC Autoforge software package. Calculated cutting forces are always bigger than measured ones. All difference between experiment and simulation is not greater than 20% . It is feasible making virtual experiment on workstation to estimate the cutting force and to predict the quality of the workpiece for new material using certain blanking technical parameters.
基金Supported by the National Natural Science Foundation of China(No.51205004,51475003)Beijing Natural Science Foundation(No.3152010)Beijing Education Committee Science and Technology Program(No.KM201510009004)
文摘The application of advanced high strength steel （AHSS） has an important significance in the development of the lightweight of automobile, but the parts made of AHSS usually have defects, such as fracture and large amount of springback, etc. In this paper, a model of multi-pass roll form- ing and springback process of AHSS is established with finite element software ABAQUS. Then a roll forming experiment is performed, and simulation and experimental results have been compared and analyzed. The model is established under complex contact conditions, including self-contact condi- tion. The results shows that during the process of sheet bending, large Mises stresses appear at ben- ding corners. The smaller the bending radius is, the larger the Mises stress and strain are. Thick- ness of sheet metal changes exceeds a certain limit, the differently if the bending radius is different. When the bending radius change tendency of the sheet thickness turns from increase to decrease.
基金This work was supported by the Brain Korea 2lProject and the Grallt of Post-Doc Program, KyungpookNational University (1999).
文摘Some techniques such as die surface description, contact judgement algorithm and remeshing are proposed to improve the robustness of the numerical solution. Based on these techniques, a three-dimensional rigid-plastic FEM code has been developed. Isothermal forging process of a cylindrical housing has been simulated. The simulation results show that the given techniques and the FEM code are reasonable and feasible for three-dimensional bulk forming processes.
文摘The precision forging process is simulated by commercial software Deform 3D using a rigid visco-plastic model to predict the status of metal flow and the distribution of equivalent plastic strain, providing guidance for making decision on the optimal choice of process parameters and mould structure. Trial forging was used to verify the effectiveness of FEM simulation results.
文摘Laser forming involves heating sheet metal workpiece along a certain path with adefocused laser beam directed irradiate to the surface. During laser forming, a tran-sient temperature fields is caused by the irradiation and travelling of a laser beam.Consequently, thermal expansion and contraction take place, and allows the thermal-mechanical forming of complex shapes. This is a new manufacturing technique thatforming metal sheet only by thermal stress. Therefore, the analysis of temperaturefields and stress fields are very useful for studying the forming mechanism and con-trolling the accuracy of laser forming. The non--liner finite element solver, MARC, isemployed to solve the thermal--mechanical analysis. Using this model, the stress andstrain distribution of pure aluminum plate with different thickness are analyzed. Theinfluence of scanning speed on temperature fields and plastic strain of metal sheet un-der the condition of constant line energy are also presented. Numerical results agreewell with the experimental results.
文摘The coupling mechanism in freezing process of seepage ground was studied and a simplified coupling math model was proposed. The nonlinear and coupling problems of PDEs were well solved using the exponential function, error function and normal distribution function, and a series of FEM equations of coupled fields of temperature and seepage were deduced and put forward. With the example of shaft ground freezing, the formation of freezing wall in seepage ground was simulated.
文摘Induction heating has been widely used by the heat treatment industry mainly in the wind-power and automotive sectors,in particular for hardening purposes,in a broad range of applications,its main advantages being the high repeatability and easy automation of the process,both factors leading to improved manufacturing efficiency and reduced CO;emissions.Though,traditional furnace-based case hardening treatments still represent the choice of reference when performance requirements are particularly demanding,either for the critical operating conditions or safety-related issues.The processes of CIH（Contour Induction Hardening）,compared to the traditional carburizing processes,allows to reduce the deformations after heat treatment.The main purpose of these treatments,as well as increases the surface hardness of the piece,is to induce compressive stresses in the superficial layer,improving the fatigue behavior.A multiphysics magneto-thermal simulation can be developed in order to calculate the temperature distribution in the gear,setting the input parameters such as currents,frequencies and treatment times.
文摘The modeling and identification of anisotropic damping property of Ni based single crystal alloys are presented. The anisotropic material damping property is modeled by 3 D rheological equations and identified by using specimen modal damping ratios and FEM simulation. The measured damping ratios which exhibit strong anisotropy are predicted better by the method presented than by other methods.
文摘In this paper the soft medium tube expanding process of different loading case and tube sheet structure is simulated with FEM. The expanding patterns under different conditions are obtained. The correction of the Single-tube Model is verified, and cor- responding procedures are also proposed to correct the error.
基金supported by the Open Fund (PLN 201718) of State Key Laboratory of Oil and Gas Reservoir Geology and ExploitationSouthwest Petroleum University and the Open Fund (SEC-2018-04) of Collaborative Innovation Center of Shale Gas Resources and EnvironmentSouthwest Petroleum University and the National Science and Technology Major Project of China (2017ZX05036003-003)
文摘Fracture prediction is a technical issue in the field of petroleum exploration and production worldwide.Although there are many approaches to predict the distribution of cracks underground,these approaches have some limitations.To resolve these issues,we ascertained the relation between numerical simulations of tectonic stress and the predicted distribution of fractures from the perspective of geologic genesis,based on the characteristics of the shale reservoir in the Longmaxi Formation in Dingshan;the features of fracture development in this reservoir were considered.3 D finite element method(FEM)was applied in combination with rock mechanical parameters derived from the acoustic emissions.The paleotectonic stress field of the crack formation period was simulated for the Longmaxi Formation in the Dingshan area.The splitting factor in the study area was calculated based on the rock breaking criterion.The coefficient of fracture development was selected as the quantitative prediction classification criteria for the cracks.The results show that a higher coefficient of fracture development indicates a greater degree of fracture development.On the basis of the fracture development coefficient classification,a favorable area was identified for the development of fracture prediction in the study area.The prediction results indicate that the south of the Dingshan area and the DY3 well of the central region are favorable zones for fracture development.
文摘Chatter vibration is a major obstacle inachieveing increased machining performance. In thisresearch, a finite element model of chip formation in a 2Dmilling process is used to predict the occurrence of chattervibrations, and to investigate the effects of variousmachining parameters on this phenomenon. The dynamicproperties of the machine tool at the tool tip are obtainedbased on experimental modal analysis, and are used in themodel as the cutter dynamics. The model allows for thenatural development of vibration as the result of the chip-tool engagement, and accounts for various phenomena thatoccur at the chip-tool interface ultimately leading tostable or unstable cutting. The model was used todemonstrate the effects of the machining parameters, suchas the axial depth of cut, radial immersion, and feed rate,on the occurrence of chatter. Additionally, the phenomenonof jumping out of the cut region could be observed in thismodel and its effect on the chatter process is demonstrated.The numerical model is verified based on comparisons withexperimental results.
基金Project(50925417)supported by the National Science Fund for Distinguished Young Scholars of China
文摘True stress?true strain curves of Incoloy028alloy at high temperature and strain rate were investigated by hot compression test.These curves show that the maximum flow stress decreases with the increase in temperature and the decrease in strain rate.FEM simulation was employed to investigate the influence of temperature,extrusion speed and friction coefficient on the extrusion load,stress,strain and strain rate in the extrusion process.The increase of extrusion temperature results in decrease of load and deformation resistance,but has little influence on strain and strain rate.When extrusion speed changes between200and350mm/s,no obvious change about extrusion load can be found.Sharp peak value up to42500kN emerges in the extrusion load curve and the extrusion process becomes unstable seriously when extrusion speed rises up to400mm/s.Both stress and strain rate increase with the raise of extrusion speed.When friction coefficient is between0.02and0.03,deformation resistance is about160MPa and the strain rate can be limited below70s?1.Successful production of Incoloy028tube verifies the optimized parameters by FEM simulation analysis,and mechanical tests results of the products meet the required properties.
文摘The samples obtained by Finite Element Method (FEM) simulation for section extrusion process have been trained on BP Neural Networks. The mapping relationsbetween die's geometrical parameters and energetic parameters, such as stress and strain generated in the die are established. The extrusion process model and its expert system are also determined. The excellent expansibility this system possesses provides a new prospect for the future development of expert system for section extrusion dies.
基金The project supported by the Hong Kong Research Grant Council(RGC)(HKUST 6079/00E)the National Natural Science Foundation of China(10532020).
文摘Finite element simulations are carried out to examine the mechanical behavior of the metallic hollow sphere （MHS） material during their large plastic deformation and to estimate the energy absorbing capacity of these materials under uniaxial compression. A simplified model is proposed from experimental observations to describe the connection between the neighboring spheres, which greatly improves the computation efficiency. The effects of the governing physical and geometrical parameters are evaluated; whilst a special attention is paid to the plateau stress, which is directly related to the energy absorbing capacity. Finally, the empirical functions of the relative material density are proposed for the elastic modulus, yield strength and plateau stress for FCC packing arrangement of hollow spheres, showing a good agreement with the experimental results obtained in our previous study.
文摘In the hot forming of Mn18Cr18N steel, such problems as easy cracking, difficult controlling of forming paramenters often occur. In this paper,the variation rule of the plasticity of the steel, the starting mechanism of micro-crack and its generating characteristics were studied with the combination of thermodynamic simulation test, micro-simulation and FEM, the related data of microstructure change and hot forming parameters were produced. The hot forming process of 600MW generator retaining ring was analyzed as an example.
文摘The high temperature split Hopkinson pressure bar （SHPB） compression experiment is conducted to obtain the data relationship among strain, strain rate and flow stress from room temperature to 550 C for aeronautical aluminum alloy 7050-T7451. Combined high-speed orthogonal cutting experiments with the cutting process simulations, the data relationship of high temperature, high strain rate and large strain in high-speed cutting is modified. The Johnson-Cook empirical model considering the effects of strain hardening, strain rate hardening and thermal softening is selected to describe the data relationship in high-speed cutting, and the material constants of flow stress constitutive model for aluminum alloy 7050-T7451 are determined. Finally, the constitutive model of aluminum alloy 7050-T7451 is established through experiment and simulation verification in high-speed cutting. The model is proved to be reasonable by matching the measured values of the cutting force with the estimated results from FEM simulations.
基金Projected(51775068)supported by the National Natural Science Foundation of China.
文摘The hot deformation behavior of Ti-6 Al-4 V-0.1 Ru titanium alloy was investigated by isothermal compression tests on a Gleeble-3500 thermal simulator over deformation temperature range of 1023-1423 K and strain rate of 0.01-10 s-1.Arrhenius-type constitutive models were developed for temperature ranges of bothα+βdual phase andβsingle phase at strain of 0.1.Afterwards,a series of material constants(including activation energy Q,material constants n,αand ln A)as polynomial functions of strain were introduced into Arrhenius-type models.Finally,the improved Arrhenius-type models in temperature field ofα+βandβphase were constructed.The results show that the improved Arrhenius-type models contribute to the calculation of Zener-Hollomon(Z)parameter,and the microstructural evolution mechanism is uncovered by combining microstructure observations with Z-parameter.Furthermore,the improved Arrhenius-type models are also helpful to improve the accuracy of finite element method(FEM)simulation in the deformation process of Ti-6 Al-4 V-0.1 Ru titanium alloy.
