Influence of defects on fatigue crack propagation in laser hybrid welded eccentric fillet joint

Fatigue cracking of laser hybrid welded eccentric fillet joints has been studied for stainless steel. Two-dimensional linear elastic fracture mechanics analysis was carried out for this joint geometry for four point bending load. The numerical simulations explain for the experimental observations why the crack propagates from the lower weld toe and why the crack gradually bends towards the root. Lack of fusion turned out to be uncritical for the initiation of cracks due to its compressive stress conditions. The linear elastic fracture mechanics analysis has demonstrated in good qualitative agreement with fatigue test results that lack of fusion slightly (<10%) reduces the fatigue life by accelerating the crack propagation. For the geometrical conditions studied here improved understanding of the crack propagation was obtained and in turn illustrated. The elaborated design curves turned out to be above the standard recommendations.

► Crack first propagates normal to the local weld surface, preferably at the lower toe, but then gradually bends to the root. ► Lack of fusion slightly (<10%) reducing the fatigue life for the case studied here. ► Higher slope (m = 3.16) of the S–N curves was obtained for hybrid laser welded eccentric fillet joints.