A meshless numerical simulation method, the moving-particle semi-implicit method （MPS） is presented in this paper to study the sloshing phenomenon in ocean and naval engineering. As a meshless method, MPS uses parti...A meshless numerical simulation method, the moving-particle semi-implicit method （MPS） is presented in this paper to study the sloshing phenomenon in ocean and naval engineering. As a meshless method, MPS uses particles to replace the mesh in traditional methods, the governing equations are discretized by virtue of the relationship of particles, and the Poisson equation of pressure is solved by incomplete Cholesky conjugate gradient method （ICCG）, the free surface is tracked by the change of numerical density. A numerical experiment of viscous liquid sloshing tank was presented and compared with the result got by the difference method with the VOF, and an additional modification step was added to make the simulation more stable. The results show that the MPS method is suitable for the simulation of viscous liquid sloshing, with the advantage in arranging the particles easily, especially on some complex curved surface.展开更多
In this paper we introduce a class of iterative methods for solution of monotone variational inequalities. The method can be viewed as an extension of the Levenberg-Marquardt method for unconstrained optimization, or ...In this paper we introduce a class of iterative methods for solution of monotone variational inequalities. The method can be viewed as an extension of the Levenberg-Marquardt method for unconstrained optimization, or the generalization of the Douglas-Rachford operator splitting methods when applied to monotone variational inequalities. Each iteration of the method consists essentially of solving a system of nonlinear equations. The convergence proof for the presented method is very展开更多
The precision forming of thin-walled components has been urgently needed in aviation and aerospace field. However, the wrinkling induced by the compressive instability is one of the major defects in thin-walled part f...The precision forming of thin-walled components has been urgently needed in aviation and aerospace field. However, the wrinkling induced by the compressive instability is one of the major defects in thin-walled part forming. The initiation and growth of the wrinkles are interac- tively affected by many factors such as stress states, mechanical properties of the material, geometry of the workpiece and boundary conditions. Especially when the forming process involves compli- cated boundary conditions such as multi-dies constrains, the perturbation of clearances between workpiece and dies and the contact conditions changing in time and space, etc., the predication of the wrinkling is further complicated. In this paper, the cu.rent prediction methods were summa- rized including the static equilibrium method, the energy method, the initial imperfection method, the eigenvalue buckling analysis method, the static-implicit finite element method and the dynamic- explicit finite element method. Then, a systematical comparison and summary of these methods in terms of their advantages and limitations are presented. By using a combination of explicit FE method, initial imperfection and energy conservation, a hybrid method is recommended to predict plastic wrinkling in thin-walled part forming. Finally, considering the urgent requirements of com- plex thin-walled structures＇ part in aviation and aerospace field, the trends and challenges in wrin- kling prediction under complicated boundary conditions are presented.展开更多
基金the National Natural Science Foundation under Grant No.50579035
文摘A meshless numerical simulation method, the moving-particle semi-implicit method （MPS） is presented in this paper to study the sloshing phenomenon in ocean and naval engineering. As a meshless method, MPS uses particles to replace the mesh in traditional methods, the governing equations are discretized by virtue of the relationship of particles, and the Poisson equation of pressure is solved by incomplete Cholesky conjugate gradient method （ICCG）, the free surface is tracked by the change of numerical density. A numerical experiment of viscous liquid sloshing tank was presented and compared with the result got by the difference method with the VOF, and an additional modification step was added to make the simulation more stable. The results show that the MPS method is suitable for the simulation of viscous liquid sloshing, with the advantage in arranging the particles easily, especially on some complex curved surface.
文摘In this paper we introduce a class of iterative methods for solution of monotone variational inequalities. The method can be viewed as an extension of the Levenberg-Marquardt method for unconstrained optimization, or the generalization of the Douglas-Rachford operator splitting methods when applied to monotone variational inequalities. Each iteration of the method consists essentially of solving a system of nonlinear equations. The convergence proof for the presented method is very
基金the National Natural Science Foundation of China(Nos.5090514451275415)National Basic Research Program of China(No.2010CB731701)+2 种基金Program for New Century Excellent Talents in University,Fundamental Research Funds for the Central Universities(3102014KYJD001)of Chinathe EU Marie Curie Actions–Mat Pro Future Project(FP7-PEOPLE-2012-IRSES-318968)of Chinathe‘‘111"Project(B08040)of China for the support to this research
文摘The precision forming of thin-walled components has been urgently needed in aviation and aerospace field. However, the wrinkling induced by the compressive instability is one of the major defects in thin-walled part forming. The initiation and growth of the wrinkles are interac- tively affected by many factors such as stress states, mechanical properties of the material, geometry of the workpiece and boundary conditions. Especially when the forming process involves compli- cated boundary conditions such as multi-dies constrains, the perturbation of clearances between workpiece and dies and the contact conditions changing in time and space, etc., the predication of the wrinkling is further complicated. In this paper, the cu.rent prediction methods were summa- rized including the static equilibrium method, the energy method, the initial imperfection method, the eigenvalue buckling analysis method, the static-implicit finite element method and the dynamic- explicit finite element method. Then, a systematical comparison and summary of these methods in terms of their advantages and limitations are presented. By using a combination of explicit FE method, initial imperfection and energy conservation, a hybrid method is recommended to predict plastic wrinkling in thin-walled part forming. Finally, considering the urgent requirements of com- plex thin-walled structures＇ part in aviation and aerospace field, the trends and challenges in wrin- kling prediction under complicated boundary conditions are presented.
