Numerical simulation of microscopic residual stress evolution in polycrystalline aggregate subjected to weld thermal cycle

Abstract

Weld residual stress affects joint performance in terms of the fatigue life and resistance to stress corrosion cracking. Thus far, the weld residual stress has been discussed mainly at the scale of the joint—the macroscopic scale. However, the weld residual stress can be inhomogeneous at the microscopic scale like a crystal grain; this aspect has not been discussed well. In this study, a numerical simulation model was developed to calculate the inhomogeneous distribution of the microscopic residual stress, based on the both-ends-fixed bar model. The bar was modeled by a polycrystalline aggregate, and the elastic and plastic anisotropy were defined for each grain. Thermal cycles with various peak temperatures were applied on the both-ends-fixed polycrystalline bar, and the evolution of the microscopic stress was simulated. The elastic and plastic anisotropy of the grains affected the inhomogeneity of the microscopic stress distribution. Elastic anisotropy caused inhomogeneity under elastic loading, whereas plastic anisotropy affected that under plastic loading. It was demonstrated that a microscopic stress higher than the applied macroscopic stress was generated when anisotropy was taken into consideration.