This study by S. Daneshpour et al. investigates the effects of overload on fatigue crack propagation in the welding of aerospace-grade aluminum alloy 2139-T8 sheets using laser beam welding. Using experimental methods and finite element (FE) analyses, the fatigue crack behaviors in 3.2 mm thick welded panels were compared with those of homogeneous base materials.

Crack Tip Plasticity:

Crack tip plasticity in homogeneous M(T) specimens was determined using the Irwin method.

The plastic strain at the crack tip under single overload was calculated for both homogeneous and welded specimens using finite element analysis.

Overload and Crack Delay:

Crack delay caused by overload in the welded specimens was explained using the Wheeler Model.

The crack tip plastic region size was calculated in the welded specimens using the maximum plastic region expansion.

Results:

Single overload resulted in larger fatigue crack delay in welded specimens compared to the base metal.

However, after periodic multiple overloads, the crack delay in low-strength welds was shorter than in the base metal.

This study highlights the effects of overload on fatigue crack propagation in laser-welded joints and demonstrates the applicability of the Wheeler Model for heterogeneous welded structures.

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