A new rigid-plastic/rigid-viscoplastic (RP/RVP) FEM based on linearprogramming (LP) for plane-strain metal forming simulation is proposed. Compared with thetraditional RP/RVP FEM based on iteration solution, it has so...A new rigid-plastic/rigid-viscoplastic (RP/RVP) FEM based on linearprogramming (LP) for plane-strain metal forming simulation is proposed. Compared with thetraditional RP/RVP FEM based on iteration solution, it has some remarkable advantages, such a it'sfree of convergence problem and its convenience in contact, incompressibility constraint and rigidzone treatment. Two solution examples are provided to validate its accuracy and efficiency.展开更多
This paper studies the dynamic behavior of large deformation of spherical shells impacted by a flat-nosed missile.By using isometric transformations,the deformation modes are given.On the basis of Perzyna-Symonds visc...This paper studies the dynamic behavior of large deformation of spherical shells impacted by a flat-nosed missile.By using isometric transformations,the deformation modes are given.On the basis of Perzyna-Symonds viscoplastic constitutive equations,the motion equations of the shells are obtained by rigid- viscoplastic variational principle.A comparison made between the numerical results and experimental ones indicates that the two groups of results are in conformity with each other.展开更多
In order to eliminate forging defects appearing in production,based on the rigid-viscoplastic FEM principle,the DEFORM3D software package was employed to simulate the forming process of TC4 alloy mounting part and to ...In order to eliminate forging defects appearing in production,based on the rigid-viscoplastic FEM principle,the DEFORM3D software package was employed to simulate the forming process of TC4 alloy mounting part and to optimize the process parameters.In this simulation,the temperature dependency of the thermal and mechanical properties of material was considered.Based on the simulation,the metal flow and thermomechanical field variables such as stress and damage are obtained.The simulation results show that the forging defects are caused by improper die dimension and the optimized die dimension was proposed.To verify the validity of simulation results,forging experiments were also carried out in a forging plant.The forging experiments show that the optimized die dimension can ensure the quality of forging part,and it can provide reference to improve and optimize die design process.展开更多
3-D rigid-viscoplastic FEM of compressible materials was applied to analyze the deformation behavior during twist compression forming of axisymmetrical body at high temperatures. When calculating the temperature fiel...3-D rigid-viscoplastic FEM of compressible materials was applied to analyze the deformation behavior during twist compression forming of axisymmetrical body at high temperatures. When calculating the temperature fields, considering the thermo mechanical coupling effect between temperature and deformation, 2-D FEM and CNG methods were adopted, and the up winding technique was used to avoid the influences of numerical instability on calculated results.展开更多
The closed die forging(or fully-enclosed die forging) method was employed to form a rotor instead of the conventional machining method. A combined female die was designed so that the rotor could be released easily fro...The closed die forging(or fully-enclosed die forging) method was employed to form a rotor instead of the conventional machining method. A combined female die was designed so that the rotor could be released easily from the female die after forging. In order to improve the metal flow ability, the isothermal forming technique was introduced to the closed die forging process. On the basis of the rigid-viscoplastic FEM principle, the DEFORM 3D software package was employed to simulate the forming process. The simulation results illustrate that the deformation of different part of the billet is not the same. The material near the entrance of the die cavity is deformed greatly whose strain rate and strain are both large, while the deformation of the material at the billet center is much smaller.展开更多
Plastic variational principles are foundation to solve the boundary-value problems of plastic mechanics with the variational method(or energy method) and finite element method.The most convenient way of establishing d...Plastic variational principles are foundation to solve the boundary-value problems of plastic mechanics with the variational method(or energy method) and finite element method.The most convenient way of establishing different kinds of variational principles is to set up the extreme principle related to the studied problem.Based on a general new extreme principle-the Least work consumption principle,the variational principles of the rigid-plastic and rigid-viscoplastic material were derived.In comparison with existing methods,the method in this paper is more clear and direct,and the physical meaning is clear-cut.This method can offer a new way for establishing other kinds of variational principles.展开更多
To avoid mesh distortion and iterative remeshing in mesh-based numerical analysis,a meshless approach based on element free Galerkin (EFG) method is applied to the metal forming analysis of ring compression. Discrete ...To avoid mesh distortion and iterative remeshing in mesh-based numerical analysis,a meshless approach based on element free Galerkin (EFG) method is applied to the metal forming analysis of ring compression. Discrete equations are formulated upon the moving least-squares (MLS) approximation and modified Markov variational principles for rigid-plastic/ rigid-viscoplastic (RP/RVP) material models. The penalty function is used for the incompressible condition without volumetric locking. Based on the axisymmetric mechanical model,ring tests with different friction coefficients are studied. The deformed nodal configurations and shaded contours of equivalent strains are shown by developed meshless post processor. The comparison of meshless and finite element (FE) results validates the feasibility and accuracy for meshless method to simulate metal forming process.展开更多
文摘A new rigid-plastic/rigid-viscoplastic (RP/RVP) FEM based on linearprogramming (LP) for plane-strain metal forming simulation is proposed. Compared with thetraditional RP/RVP FEM based on iteration solution, it has some remarkable advantages, such a it'sfree of convergence problem and its convenience in contact, incompressibility constraint and rigidzone treatment. Two solution examples are provided to validate its accuracy and efficiency.
基金This subject was SHpported by the Natural Science Foundation of Shanxi
文摘This paper studies the dynamic behavior of large deformation of spherical shells impacted by a flat-nosed missile.By using isometric transformations,the deformation modes are given.On the basis of Perzyna-Symonds viscoplastic constitutive equations,the motion equations of the shells are obtained by rigid- viscoplastic variational principle.A comparison made between the numerical results and experimental ones indicates that the two groups of results are in conformity with each other.
基金Project(2005400201) supported by the Aeronautical Science Foundation of Liaoning Province,China
文摘In order to eliminate forging defects appearing in production,based on the rigid-viscoplastic FEM principle,the DEFORM3D software package was employed to simulate the forming process of TC4 alloy mounting part and to optimize the process parameters.In this simulation,the temperature dependency of the thermal and mechanical properties of material was considered.Based on the simulation,the metal flow and thermomechanical field variables such as stress and damage are obtained.The simulation results show that the forging defects are caused by improper die dimension and the optimized die dimension was proposed.To verify the validity of simulation results,forging experiments were also carried out in a forging plant.The forging experiments show that the optimized die dimension can ensure the quality of forging part,and it can provide reference to improve and optimize die design process.
文摘3-D rigid-viscoplastic FEM of compressible materials was applied to analyze the deformation behavior during twist compression forming of axisymmetrical body at high temperatures. When calculating the temperature fields, considering the thermo mechanical coupling effect between temperature and deformation, 2-D FEM and CNG methods were adopted, and the up winding technique was used to avoid the influences of numerical instability on calculated results.
文摘The closed die forging(or fully-enclosed die forging) method was employed to form a rotor instead of the conventional machining method. A combined female die was designed so that the rotor could be released easily from the female die after forging. In order to improve the metal flow ability, the isothermal forming technique was introduced to the closed die forging process. On the basis of the rigid-viscoplastic FEM principle, the DEFORM 3D software package was employed to simulate the forming process. The simulation results illustrate that the deformation of different part of the billet is not the same. The material near the entrance of the die cavity is deformed greatly whose strain rate and strain are both large, while the deformation of the material at the billet center is much smaller.
文摘Plastic variational principles are foundation to solve the boundary-value problems of plastic mechanics with the variational method(or energy method) and finite element method.The most convenient way of establishing different kinds of variational principles is to set up the extreme principle related to the studied problem.Based on a general new extreme principle-the Least work consumption principle,the variational principles of the rigid-plastic and rigid-viscoplastic material were derived.In comparison with existing methods,the method in this paper is more clear and direct,and the physical meaning is clear-cut.This method can offer a new way for establishing other kinds of variational principles.
文摘To avoid mesh distortion and iterative remeshing in mesh-based numerical analysis,a meshless approach based on element free Galerkin (EFG) method is applied to the metal forming analysis of ring compression. Discrete equations are formulated upon the moving least-squares (MLS) approximation and modified Markov variational principles for rigid-plastic/ rigid-viscoplastic (RP/RVP) material models. The penalty function is used for the incompressible condition without volumetric locking. Based on the axisymmetric mechanical model,ring tests with different friction coefficients are studied. The deformed nodal configurations and shaded contours of equivalent strains are shown by developed meshless post processor. The comparison of meshless and finite element (FE) results validates the feasibility and accuracy for meshless method to simulate metal forming process.
