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
In routine design of tensioned membrane structures, the membrane is generally modeled using space membrane elements and the cables by space cable elements, with no sliding allowed between the membrane and the cables. ...In routine design of tensioned membrane structures, the membrane is generally modeled using space membrane elements and the cables by space cable elements, with no sliding allowed between the membrane and the cables. On the other hand, large deflections are expected and sliding between the membrane and the cables is inevitable. In the present paper, the general finite element code ABAQUS was employed to investigate the influence of cable sliding on membrane surface on the structural behavior. Three analysis models were devised to fulfill this purpose: (1) The membrane element shares nodes with the cable element; (2) The cable can slide on the membrane surface freely (without friction) and (3) The cable can slide on the membrane surface, but with friction between the cable and the membrane. The sliding problem is modeled using a surface - based contact algorithm. The results from three analysis models are compared, showing that cable sliding has only little influence on the structure shape and on the stress distributions in the membrane. The main influence of cable sliding may be its effect on the dynamic behavior of tensioned membrane structures.展开更多
With the increased use of automotive engine start-stop systems,the numerical prediction and reduction of frictional losses in sliding bearings during starting and stopping procedures has become an important issue.In e...With the increased use of automotive engine start-stop systems,the numerical prediction and reduction of frictional losses in sliding bearings during starting and stopping procedures has become an important issue.In engineering practice,numerical simulations of sliding bearings in automotive engines are performed with statistical asperity contact models with empirical values for the necessary surface parameters.The aim of this study is to elucidate the applicability of these approaches for the prediction of friction in sliding bearings subjected to start-stop operation.For this purpose,the friction performance of sliding bearings was investigated in experiments on a test rig and in transient mixed elasto-hydrodynamic simulations in a multi-body simulation environment(mixed-EHL/MBS).In mixed-EHL/MBS,the extended Reynold’s equation with flow factors according to Patir and Cheng has been combined on the one hand with the statistical asperity contact model according to Greenwood and Tripp and on the other hand with the deterministic asperity contact model according to Herbst.The detailed comparison of simulation and experimental results clarifies that the application of statistical asperity contact models with empirical values of the necessary inputs leads to large deviations between experiment and simulation.The actual distribution and position of surface roughness,as used in deterministic contact modelling,is necessary for a reliable prediction of the frictional losses in sliding bearings during start-stop operation.展开更多
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In routine design of tensioned membrane structures, the membrane is generally modeled using space membrane elements and the cables by space cable elements, with no sliding allowed between the membrane and the cables. On the other hand, large deflections are expected and sliding between the membrane and the cables is inevitable. In the present paper, the general finite element code ABAQUS was employed to investigate the influence of cable sliding on membrane surface on the structural behavior. Three analysis models were devised to fulfill this purpose: (1) The membrane element shares nodes with the cable element; (2) The cable can slide on the membrane surface freely (without friction) and (3) The cable can slide on the membrane surface, but with friction between the cable and the membrane. The sliding problem is modeled using a surface - based contact algorithm. The results from three analysis models are compared, showing that cable sliding has only little influence on the structure shape and on the stress distributions in the membrane. The main influence of cable sliding may be its effect on the dynamic behavior of tensioned membrane structures.
基金This work was funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)-GRK 1856.
文摘With the increased use of automotive engine start-stop systems,the numerical prediction and reduction of frictional losses in sliding bearings during starting and stopping procedures has become an important issue.In engineering practice,numerical simulations of sliding bearings in automotive engines are performed with statistical asperity contact models with empirical values for the necessary surface parameters.The aim of this study is to elucidate the applicability of these approaches for the prediction of friction in sliding bearings subjected to start-stop operation.For this purpose,the friction performance of sliding bearings was investigated in experiments on a test rig and in transient mixed elasto-hydrodynamic simulations in a multi-body simulation environment(mixed-EHL/MBS).In mixed-EHL/MBS,the extended Reynold’s equation with flow factors according to Patir and Cheng has been combined on the one hand with the statistical asperity contact model according to Greenwood and Tripp and on the other hand with the deterministic asperity contact model according to Herbst.The detailed comparison of simulation and experimental results clarifies that the application of statistical asperity contact models with empirical values of the necessary inputs leads to large deviations between experiment and simulation.The actual distribution and position of surface roughness,as used in deterministic contact modelling,is necessary for a reliable prediction of the frictional losses in sliding bearings during start-stop operation.
