Three-dimensional surface fatigue crack growth life assessment model of steel welded joints and structures

Abstract

To investigate the fatigue crack growth of surface cracks in steel welded joints, a three-dimensional surface fatigue crack growth life assessment model considering both the surface crack growth period and the following through crack growth period is proposed. The fatigue crack growth life of a standard steel butt joint specimen is predicted considering the effect of welding residual stress and it is compared with fatigue test results. An example of a welded beam-to-column connection in a steel high-rise building under wind is selected to demonstrate the improvement of the model to make it applicable to stochastic loading and real engineering structures. The life results are compared with those obtained by other fatigue assessment approaches. The mesh sensitivity analysis is made and the effect of extreme welding imperfections and corrosion environment are both discussed. Guidance to select the fatigue life assessment approaches is also proposed. The results show that the growth shape of the edge crack remains a quarter of a circle while that of the center crack remains a quarter of an ellipse during the growth; When the surface crack grows through the plate thickness and becomes a through crack, the remaining fatigue crack growth life is unneglectable for real engineering components especially for the ones with a large plate width; The effect of welding residual stress on the fatigue crack growth life of real engineering component is complex and it depends on the distribution of the residual stress itself; The proposed three-dimensional surface crack engineering model can acquire accurate life results and is applicable to stochastic loading and engineering structures.

Fatigue life prediction of aluminum alloy T‐welded joints root failure based on equivalent crack method

“…Linear elastic fracture mechanics is an excellent solution for structures with initial weld defects, and the method has been very well studied 18,20 . However, numerical simulations for weld root cracking have been little studied.…”

“…As one of the critical factors affecting life, the residual stress of the welded structure must be considered in the crack growth simulation 19,20 . According to the superposition principle of influential stress intensity factors, the impact of residual stress on fatigue life prediction can be quantitatively evaluated 37 .…”

“…Linear elastic fracture mechanics is an excellent solution for structures with initial weld defects, and the method has been very well studied. 18,20 However, numerical simulations for weld root cracking have been little studied. This study develops a comprehensive numerical model for initial defect fracture of the T-weld root based on the physical structure.…”

“…[Colour figure can be viewed at wileyonlinelibrary.com] crack growth simulation. 19,20 According to the superposition principle of influential stress intensity factors, the impact of residual stress on fatigue life prediction can be quantitatively evaluated. 37 In this paper, the influence of residual stress on the life of the welded structure is considered based on the mean stress method, and the influence of external load and residual stress on the stress intensity factor at the crack tip is superimposed and characterized by K eff , as given by the following equation:…”

“…The crack geometry and extension were essentially three‐dimensional, and the fracture profiles of the numerical model were generally in good agreement with the corresponding experimental profiles. Zhao et al 19 and Fang et al 20 performed 3D simulations of the welding process and fatigue crack extension, considering the weld geometry and redistribution of residual stresses. The above recent literature provides an in‐depth study around crack growth simulation, where initial defects, residual stresses, and crack growth rate remain the main factors affecting crack growth life.…”