Utility of Step Iterative Total Strain Method with Large Increment of Temparature

—Development of Effective and Accurate Method of Thermal Elastic-Plastic Analysis for Shortening of Computation Time (2nd Report)—

Abstract

The thermal elastic-plastic analysis for the welding transient and residual stresses and deformations needs the huge computation time to obtain the accurate results. In this study, a new method, a step iterative total strain method, was developed to shorten the computation time largely, keeping high accuracy. The theory can take account of not only the temperature-dependencies of the mechanical properties, as usual thermal elastic-plastic theory, but also the change from elastic state to elastic-plastic state in one large temperature increment. Based on the theory (the thermal elastic-plastic constitutive equation), the equilibrium equation (the stiffness equation) was developed in the finite element method (FEM). New FEM program for thermal elastic-plastic analysis was developed, based on the above theory. A simple important problem of thermal elastic-plastic behavior was analyzed to verify the capability (accuracy) of the new method. In this report, some complex typical welding problems were analyzed. The residual stresses and deformations were compared with the accurate results obtained by the usual incremental method with very small temperature increments. As a result, it was confirmed that the computation time is very largely shortened, compared with the usual incremental method, keeping the high accuracy.