Improvement in numerical accuracy and stability of 3-D FEM analysis in welding

The finite element method (FEM) of modeling and the rapid development of computer architecture provide the possibility of analyzing complex problems such as those encountered in welding processes where structures undergo a large temperature cycle. Due to the temperature dependence of material properties and the large deformation in welding, both material and geometrical nonlinearity must be taken into account. It is also important to ensure numerical accuracy and stability, especially at high temperature stages. Previous investigations in thermal elastic-plastic analysis showed that the stages with drastic change (such as the transition stage from elastic to plastic and unloading stage) suffered from numerical error. It has also been shown that the mesh size and temperature incremental used in the nonlinear computation has a significant influence on the accuracy of the solution. To improve the accuracy of the numerical solution, weighting factors are introduced to take into account the transition from elastic stage to plastic stage as well as the temperature dependence of material properties. In order to prevent the numerical locking phenomena, a reduced integration method is presented in the 3-D solid elements with a local coordinate system. The effectiveness of the proposed methods is demonstrated through a 3-D analysis ofmore » a compressor assembled with plug welds.« less