Based on existing algorithms, a newly developed contact search algorithm is proposed. The new algorithm consists of global search, local searching, local tracking and penetration calculation processes. It requires no ...Based on existing algorithms, a newly developed contact search algorithm is proposed. The new algorithm consists of global search, local searching, local tracking and penetration calculation processes. It requires no iteration steps. It can deal with not only general tool surfaces with vertical walls, but also tool surfaces meshed with elements having very poor aspect ratios. It is demonstrated that the FE code employing this new contact search algorithm becomes more reliable, efficient and accurate for sheet metal forming simulation than conventional ones.展开更多
The Explicit Upstream FEM (EU-FEM) proposed in this paper not only possesses the advantages of saving memory and CPU time for FDM, but also fits boundary easily, arranges nodal points flexibly and makes local grids fi...The Explicit Upstream FEM (EU-FEM) proposed in this paper not only possesses the advantages of saving memory and CPU time for FDM, but also fits boundary easily, arranges nodal points flexibly and makes local grids fine down conveniently. The software package, which consists of EU-FEM models and pre/post-processing skills, has been widely used to estuary, near-shore, bay, lake and complex waters with many islands and channels. In addition to flow field, this model can be used to calculate the distribution fields of pollutants, temperature, salinity, sediment, and oil spill, and can be used to case study of estuary regulation projects. Some practical applications are presented and some problems discussed.展开更多
The quasi-static explicit finite element method (FEM) and element free Galerkin (EFG) method are applied to trace the post-buckling equilibrium path of thin-walled members in this paper. The factors that primarily con...The quasi-static explicit finite element method (FEM) and element free Galerkin (EFG) method are applied to trace the post-buckling equilibrium path of thin-walled members in this paper. The factors that primarily control the explicit buckling solutions, such as the computation time, loading function and dynamic relaxation, are investigated and suggested for the buckling analysis of thin-walled members. Three examples of different buckling modes, namely snap-through, overall and local buckling, are studied based on the implicit FEM, quasi-static explicit FEM and EFG method via the commercial software LS-DYNA. The convergence rate and accuracy of the explicit methods are compared with the conventional implicit arc-length method. It is drawn that EFG quasi-static explicit buckling analysis presents the same accurate results as implicit finite element solution, but is without convergence problem and of less-consumption of computing time than FEM.展开更多
A new FE modeling method of hot ring rolling was presented by solving key technologies such as contact and heat boundary conditions,motion control over guide rolls,and mass scaling.The method has the following feature...A new FE modeling method of hot ring rolling was presented by solving key technologies such as contact and heat boundary conditions,motion control over guide rolls,and mass scaling.The method has the following features:1)the elastic-plastic dynamic explicit approach instead of the static implicit approach is adopted to solve the process so as to greatly improve computational efficiency without sacrificing computational accuracy;2)the coupled thermal-mechanical effect is considered as opposed to the conventional isothermal assumption,which is more practical;3)in contrast to the simplified 2D or local 3D ring model,the full 3D ring is modeled to simulate the process.Based on the FE modeling method,two cases of hot plain ring rolling are simulated in the FEA software ABAQUS/Explicit.The simulation results are compared with the experimental measurements and the good agreement between them is observed regarding the material flow and the temperature distribution of the ring.展开更多
基金the National Natural Science F oundation of China (5 9875 0 2 5 ) and Excellent Young Teacher Founda-tion of the Educational Departm ent of China
文摘Based on existing algorithms, a newly developed contact search algorithm is proposed. The new algorithm consists of global search, local searching, local tracking and penetration calculation processes. It requires no iteration steps. It can deal with not only general tool surfaces with vertical walls, but also tool surfaces meshed with elements having very poor aspect ratios. It is demonstrated that the FE code employing this new contact search algorithm becomes more reliable, efficient and accurate for sheet metal forming simulation than conventional ones.
文摘The Explicit Upstream FEM (EU-FEM) proposed in this paper not only possesses the advantages of saving memory and CPU time for FDM, but also fits boundary easily, arranges nodal points flexibly and makes local grids fine down conveniently. The software package, which consists of EU-FEM models and pre/post-processing skills, has been widely used to estuary, near-shore, bay, lake and complex waters with many islands and channels. In addition to flow field, this model can be used to calculate the distribution fields of pollutants, temperature, salinity, sediment, and oil spill, and can be used to case study of estuary regulation projects. Some practical applications are presented and some problems discussed.
文摘The quasi-static explicit finite element method (FEM) and element free Galerkin (EFG) method are applied to trace the post-buckling equilibrium path of thin-walled members in this paper. The factors that primarily control the explicit buckling solutions, such as the computation time, loading function and dynamic relaxation, are investigated and suggested for the buckling analysis of thin-walled members. Three examples of different buckling modes, namely snap-through, overall and local buckling, are studied based on the implicit FEM, quasi-static explicit FEM and EFG method via the commercial software LS-DYNA. The convergence rate and accuracy of the explicit methods are compared with the conventional implicit arc-length method. It is drawn that EFG quasi-static explicit buckling analysis presents the same accurate results as implicit finite element solution, but is without convergence problem and of less-consumption of computing time than FEM.
基金Project(50335060) supported by the National Natural Science Foundation for Key Program of ChinaProject(50225518) supported by the National Science Fund of China for Distinguished Young Scholars
文摘A new FE modeling method of hot ring rolling was presented by solving key technologies such as contact and heat boundary conditions,motion control over guide rolls,and mass scaling.The method has the following features:1)the elastic-plastic dynamic explicit approach instead of the static implicit approach is adopted to solve the process so as to greatly improve computational efficiency without sacrificing computational accuracy;2)the coupled thermal-mechanical effect is considered as opposed to the conventional isothermal assumption,which is more practical;3)in contrast to the simplified 2D or local 3D ring model,the full 3D ring is modeled to simulate the process.Based on the FE modeling method,two cases of hot plain ring rolling are simulated in the FEA software ABAQUS/Explicit.The simulation results are compared with the experimental measurements and the good agreement between them is observed regarding the material flow and the temperature distribution of the ring.
