复杂结构动应力分析的FEM─BEM耦合法

A FEM-BEM Coupling Method in Dynamic Stress Analysis of Structure

本文提出了计算结构动应力的ＦＥＭ—ＢＥＭ耦合法．具体地建立了边界元子域的边界位移，面力及体力等的处理方法．算例表明，本文的方法具有程序实施简便，计算效率高等优点．

In Ref. [4], Brcbbia proposed FEM-BEM (finite clement method combined with boundary element method) in clastostatics. In this paper, Brebbia's FEM-BEM is further developcd to include dynamic stress analysis of structure. After a careful and extensive search, no paper in open literature on dynamic stress analysis with FEM-BEM has been found by the authors. The author uses the finite clement solution to define the boundary conditions for a boundary clement region n,Fig.l). First a global finite clement solution is found using the mesh in Fig.l and then the BEM is used to study the region Ωl in more detail, using as boundary conditions the displacements obtained in the finite clement code. As shown in equation (2), the displacements and surface forces must be given. The FE results for displacements arc usually accurate; so the key to FEM-BEM is to find the forces acting on the boundary Tl of region Ωl. The nodal forces can be calculated by equation (11). A simply-supported beam under a concentrated dynamic load is taken as example (Fig.2). Calculahons show that this method is without restrictions, and the programs can be implemented castly. The accuracy of dynamic stress computed by FEM-BEM is obviously higher than that by FEM when the frequency of excitation is high (Fig.3).