三次元熱弾塑性解析プログラムの開発と圧縮機の溶接組立への応用

Abstract

A finite element program for three dimensional thermal-elastic-plastic analysis was developed. Because of the geometrical nonlinearity and the temperature dependent material nonlinearities during welding, it is an imprortant problem how to ensure the computing accuracy and to get the stable solution, especially at a high temperature stage. Factors that may influence the accuracy and the convergence of computation were investigated. The results show that the stages with drastic change, such as transition from elastic to plastic, unloading stage, and stage in which material properties vary rapidly with temperature, suffer from the numerical error. When the solid elements are used for the bending problem of a thin plate or a shell, numerical locking phenomenon may also influence the solution.Residual deformations were analyzed by the developed program for two models taken from shrinkage fit process and plug welding process of a compressor. In the program proper methods were introduced to improve the accuracy and the convergence of numerical analysis. One of them is to use weight factors for strain increment in the stages with drastic changes in mechanical status and material properties. In order to prevent the locking phenomenon, the selective reduced integration method was adopted to the cylinder part of the compressor. The calculated deformations were compared with the measured values. The results show that good agreement can be obtained after introducing the proposed methods and that the developed program can provide satisfactory solutions. The influences of the welding conditions upon the eccentricity of assembled components in the compressor were also investigated.