Crack initiation and propagation analysis at welds – assessing the total fatigue life of complex structures

Abstract

The fatigue strength of complex welded structures may differ highly from that of a simple test specimen. The reason for this observation is in most cases the high amount of crack propagation on the total fatigue life. The aim of this work is to describe the complex failure mechanism with a two‐phase model. In this model, the crack initiation and crack propagation phase are assessed separately. The fatigue life until initiation of a crack is derived by notch stresses, calculated using stress averaging or the critical distance approach. The macro crack propagation is determined by fracture mechanics. The methods, which are available to determine the fatigue life until crack initiation, lead to reliable results. The determination of stress intensity factors proved to be demanding. Variations were observed depending on the calculation approach used. For application in industry, the applied approaches should be improved further.