Numerical Modelling of Fatigue Crack Growth of Welded Joint at Elevated Temperature

Abstract

Welding is the extensively utilized permanent joining method plays a significant role in the production and joining of massive components; pressure vessels, ship, bridge, etc. Fatigue failure of welded joints working at elevated temperatures has been a severe problem facing in the world. The leakage due to fracture in these equipment's results in disasters to human life and economy. Even though research has been reported on the fracture and fatigue of welded joint, it only focusses on the residual stresses effects and the influence of the weld toe geometry in failure criteria. The purpose of this study is to model fatigue crack growth behaviour of welded joints at elevated temperature. In this study, both analytical and finite element (FE) approaches have been used to model Welding induced residual stress, to analysis thermomechanical stress and to model thermomechanical fatigue of welded joints. In the modelling of Welding induced residual stress, the heat input during welding results in the formation of residual stress. The critical stress during the analysis of thermomechanical stress which is perpendicular to longitudinal crack growth direction is hoop (circumferential) stress. The Welding induced residual stress and high temperature effects on crack growth rate with the initial crack length are determined using the equation proposed by Forman. The elevated temperature was found to play a significant role in fatigue crack growth of welded joint works at elevated temperature with the addition of Welding induced residual stress, and thermomechanical produced stresses. Finally, the analytical and FE results were compared with the experimental result; the analytical and FE results are in good agreement with the experimental result. In this study, it was possible to model the behaviour of fatigue crack growth of welded joint at elevated temperature for low cycle fatigue.