Based on the Finite Element Theory of Rigid Plastic, relevant problems during plas-tic simulation on sheet metal forming were technologically studied and simplified; asimplified model of the blank holder during the dr...Based on the Finite Element Theory of Rigid Plastic, relevant problems during plas-tic simulation on sheet metal forming were technologically studied and simplified; asimplified model of the blank holder during the drawing process was established andthe effects of related parameters on the forming processes were also studied. At thesame time, a finite--element numerical simulation program SPID was developed. Thedistribution of strain and relationship of stress--stroke simulated were compared withexperimented, the results are well coincided with each other. It is verified that theanalytical program is reliable.展开更多
Numerical simulation and perturbation method were coupled into the iteration process for optimizing the sheet metal part stamping quality, by minimizing the risk of rupture, wrinkle and unstretched area. The optimizat...Numerical simulation and perturbation method were coupled into the iteration process for optimizing the sheet metal part stamping quality, by minimizing the risk of rupture, wrinkle and unstretched area. The optimization of the sheet metal drawing part surface was realized by adjusting the FEM node/element perturbation vector directions and values. The sweeping simplex algorithm was modified to better control the optimization process, and one step simulation code was used to verify the new design formability. Finally, an autoauto fender drawing part shape optimization testified the proposed methods successfully.展开更多
Single-point incremental forming （SPIF） is an innovational sheet metal forming method without dedicated dies, which belongs to rapid prototyping technology. In generalizing the SPIF of sheet metal, the deformation a...Single-point incremental forming （SPIF） is an innovational sheet metal forming method without dedicated dies, which belongs to rapid prototyping technology. In generalizing the SPIF of sheet metal, the deformation analysis on forming process becomes an important and useful method for the planning of shell products, the choice of material, the design of the forming process and the planning of the forming tool. Using solid brick elements, the finite element method（FEM） model of truncated pyramid was established. Based on the theory of anisotropy and assumed strain formulation, the SPIF processes with different parameters were simulated. The resulted comparison between the simulations and the experiments shows that the FEM model is feasible and effective. Then, according to the simulated forming process, the deformation pattern of SPIF can be summarized as the combination of plane-stretching deformation and bending deformation. And the study about the process parameters＇ impact on deformation shows that the process parameter of interlayer spacing is a dominant factor on the deformation. Decreasing interlayer spacing, the strain of one step decreases and the formability of blank will be improved. With bigger interlayer spacing, the plastic deformation zone increases and the forming force will be bigger.展开更多
The experimental die apparatus of the solid granules medium forming on sheet metal was designed and manufactured.Typical parts,such as conical,parabolic,cylindrical and square-box-shaped components,were successfully t...The experimental die apparatus of the solid granules medium forming on sheet metal was designed and manufactured.Typical parts,such as conical,parabolic,cylindrical and square-box-shaped components,were successfully trial-produced as well.According to the analysis of the changing trends of the cross-section shape and the wall thickness during the process,it can be found that the shape of the free deformation zone of the sheet metal,which is the most critical thinning area,can be described as an approximately spherical cap.According to this forming feature,back pressure deep drawing technology with solid granules medium on sheet metal was proposed to restrain drastic thinning at the bottom of the part through the joint friction effect of solid granules medium,the back pressure tringle and the sheet metal.Therefore,the deep drawing limit of the sheet metal is significantly improved.In order to fabricate thin-walled rotary parts with great drawing ratio and complex cross-sections,a finite element model based on the material property test of the solid granules medium was established to optimize the scheme of the back pressure deep drawing.The effects on the forming performance of sheet metal from back pressure load and the approach of blank holding control were analyzed through this model.展开更多
In order to investigate the process of incremental sheet forming (ISF) through both experimental and numerical approaches, a three-dimensional elasto-plastic finite element model (FEM) was developed to simulate the pr...In order to investigate the process of incremental sheet forming (ISF) through both experimental and numerical approaches, a three-dimensional elasto-plastic finite element model (FEM) was developed to simulate the process and the simulated results were compared with those of experiment. The results of numerical simulations, such as the strain history and distribution, the stress state and distribution, sheet thickness distribution, etc, were discussed in details, and the influences of process parameters on these results were also analyzed. The simulated results of the radial strain and the thickness distribution are in good agreement with experimental results. The simulations reveal that the deformation is localized around the tool and constantly remains close to a plane strain state. With decreasing depth step, increasing tool diameter and wall inclination angle, the axial stress reduces, leading to less thinning and more homogeneous plastic strain and thickness distribution. During ISF, the plastic strain increases stepwise under the action of the tool. Each increase in plastic strain is accompanied by hydrostatic pressure, which explains why obtainable deformation using ISF exceeds the forming limits of conventional sheet forming.展开更多
Choosing inner door panel of auto as an example, the two stage deep drawing of complex sheet metal was studied. By using CAD software UG and numerical simulation software DYNAFORM, the characteristic of the CAD modeli...Choosing inner door panel of auto as an example, the two stage deep drawing of complex sheet metal was studied. By using CAD software UG and numerical simulation software DYNAFORM, the characteristic of the CAD modeling of the simple workpiece and the complex sheet metal, finite element modeling and the selection of parameters were analyzed. The effects of three important material parameters such as yield stress, strain hardening exponent and normal anisotropic parameter on the formability of the two stage deep drawing of inner door panel of auto were investigated. The results show that the yield stress has large influence on the increase of thickness, while the strain hardening exponent has little effect on the thickness change. Otherwise, larger normal anisotropic parameter can result in a better formability of the sheet.展开更多
Due to complexities of draw-bead restraining force calculated according to theory and depending on sheet metal forming properties experiment testing system, a simplified method to calculate draw-bead restraining force...Due to complexities of draw-bead restraining force calculated according to theory and depending on sheet metal forming properties experiment testing system, a simplified method to calculate draw-bead restraining force is put forward by experimental method in cup-shaped drawing process. The experimental results were compared with numerical results and proved agreement. It shows the method is effective.展开更多
文摘Based on the Finite Element Theory of Rigid Plastic, relevant problems during plas-tic simulation on sheet metal forming were technologically studied and simplified; asimplified model of the blank holder during the drawing process was established andthe effects of related parameters on the forming processes were also studied. At thesame time, a finite--element numerical simulation program SPID was developed. Thedistribution of strain and relationship of stress--stroke simulated were compared withexperimented, the results are well coincided with each other. It is verified that theanalytical program is reliable.
基金Project(0 15 1110 0 4)supportedbyShanghaiScienceandTechnologyDevelopmentFund China
文摘Numerical simulation and perturbation method were coupled into the iteration process for optimizing the sheet metal part stamping quality, by minimizing the risk of rupture, wrinkle and unstretched area. The optimization of the sheet metal drawing part surface was realized by adjusting the FEM node/element perturbation vector directions and values. The sweeping simplex algorithm was modified to better control the optimization process, and one step simulation code was used to verify the new design formability. Finally, an autoauto fender drawing part shape optimization testified the proposed methods successfully.
基金supported by National Natural Science Foundation of China(No. 50175034).
文摘Single-point incremental forming （SPIF） is an innovational sheet metal forming method without dedicated dies, which belongs to rapid prototyping technology. In generalizing the SPIF of sheet metal, the deformation analysis on forming process becomes an important and useful method for the planning of shell products, the choice of material, the design of the forming process and the planning of the forming tool. Using solid brick elements, the finite element method（FEM） model of truncated pyramid was established. Based on the theory of anisotropy and assumed strain formulation, the SPIF processes with different parameters were simulated. The resulted comparison between the simulations and the experiments shows that the FEM model is feasible and effective. Then, according to the simulated forming process, the deformation pattern of SPIF can be summarized as the combination of plane-stretching deformation and bending deformation. And the study about the process parameters＇ impact on deformation shows that the process parameter of interlayer spacing is a dominant factor on the deformation. Decreasing interlayer spacing, the strain of one step decreases and the formability of blank will be improved. With bigger interlayer spacing, the plastic deformation zone increases and the forming force will be bigger.
基金Project(50775197) supported by the National Natural Science Foundation of China
文摘The experimental die apparatus of the solid granules medium forming on sheet metal was designed and manufactured.Typical parts,such as conical,parabolic,cylindrical and square-box-shaped components,were successfully trial-produced as well.According to the analysis of the changing trends of the cross-section shape and the wall thickness during the process,it can be found that the shape of the free deformation zone of the sheet metal,which is the most critical thinning area,can be described as an approximately spherical cap.According to this forming feature,back pressure deep drawing technology with solid granules medium on sheet metal was proposed to restrain drastic thinning at the bottom of the part through the joint friction effect of solid granules medium,the back pressure tringle and the sheet metal.Therefore,the deep drawing limit of the sheet metal is significantly improved.In order to fabricate thin-walled rotary parts with great drawing ratio and complex cross-sections,a finite element model based on the material property test of the solid granules medium was established to optimize the scheme of the back pressure deep drawing.The effects on the forming performance of sheet metal from back pressure load and the approach of blank holding control were analyzed through this model.
基金Project(50175034) supported by the National Natural Science Foundation of China
文摘In order to investigate the process of incremental sheet forming (ISF) through both experimental and numerical approaches, a three-dimensional elasto-plastic finite element model (FEM) was developed to simulate the process and the simulated results were compared with those of experiment. The results of numerical simulations, such as the strain history and distribution, the stress state and distribution, sheet thickness distribution, etc, were discussed in details, and the influences of process parameters on these results were also analyzed. The simulated results of the radial strain and the thickness distribution are in good agreement with experimental results. The simulations reveal that the deformation is localized around the tool and constantly remains close to a plane strain state. With decreasing depth step, increasing tool diameter and wall inclination angle, the axial stress reduces, leading to less thinning and more homogeneous plastic strain and thickness distribution. During ISF, the plastic strain increases stepwise under the action of the tool. Each increase in plastic strain is accompanied by hydrostatic pressure, which explains why obtainable deformation using ISF exceeds the forming limits of conventional sheet forming.
文摘Choosing inner door panel of auto as an example, the two stage deep drawing of complex sheet metal was studied. By using CAD software UG and numerical simulation software DYNAFORM, the characteristic of the CAD modeling of the simple workpiece and the complex sheet metal, finite element modeling and the selection of parameters were analyzed. The effects of three important material parameters such as yield stress, strain hardening exponent and normal anisotropic parameter on the formability of the two stage deep drawing of inner door panel of auto were investigated. The results show that the yield stress has large influence on the increase of thickness, while the strain hardening exponent has little effect on the thickness change. Otherwise, larger normal anisotropic parameter can result in a better formability of the sheet.
基金Supported by Science and Technology Development Foundation of Shanghai (015211009).
文摘Due to complexities of draw-bead restraining force calculated according to theory and depending on sheet metal forming properties experiment testing system, a simplified method to calculate draw-bead restraining force is put forward by experimental method in cup-shaped drawing process. The experimental results were compared with numerical results and proved agreement. It shows the method is effective.
