LS-Dyna学习记录.doc

1. The SOLID164 element is an 8-node brick element. By default, it uses reduced (one point) integration plus viscous hourglass control for faster element formulation. One point integration is advantageous due to savings on computer time and robustness in cases of large deformations. A fully integrated solid formulation (KEYOPT(1) = 2) is also available; see the element description for SOLID164 in the ANSYS Elements Reference and Section 3.3 of the LS-DYNA Theoretical Manual. If hourglass phenomenon is a concern, such as with foams, the fully integrated formulation may perform better because hourglass control is not required; but it is about four times more costly in terms of CPU time. Wedge, pyramid, and tetrahedra shaped elements are simply degenerate bricks (i.e., some of the nodes are repeated). These shapes are often too stiff in bending and cause problems in some situations. Therefore, these degenerate shapes should be avoided. 2. Keep the following points in mind when choosing mesh controls: Avoid degenerate shell and solid element shapes (such as a triangular shell or a tetrahedral solid). They are generally too stiff and less accurate than quadrilateral and hexahedral shapes. Try to achieve a mesh with uniform element sizes (i.e., avoid areas with relatively small elements). A large difference in element sizes can cause a small minimum time step size and, therefore, a long run time. If a relatively few number of small elements are required to mesh a particular geometry, mass scaling (seeMass Scaling) can be used to increase the minimum time step. Do not use the SmartSizing method of element size control (SMRTSIZE command), which can create a large variation in element sizes within the mesh. Instead, use theESIZE and related commands to control element sizes. Avoid poorly shaped elements which can cause hourglassing. Do not make the mesh too coarse when reduced element formulations are used, or elements may experience hourglassing. If hourglassing is a proble