The analysis of a material that is subjected to variable loads is a complex subject and generally treated separately by fatigue and fracture mechanics. We present an attempt to extend the validity of conventional fatigue approach (here strain-life) in the scope fracture. This was achieved by introducing a zero thickness cohesive contact element coupled with a damage parameter that was developed from material observations of strain controlled fatigue experiments. The presented simulation framework results in a predictable crack growth direction on a compact tension specimen, although further experimentation is needed to validate the proposed approach.

This study presents a novel approach to understanding fatigue and crack growth phenomena by benchmarking experimental observations with numerical simulations. We introduced controlled residual stress fields away from notch-induced crack nucleation sites and analyzed their interaction with crack nucleation and growth. Surprisingly, our findings revealed that the introduction of generally beneficial compressive residual stresses had a counter-intuitive negative impact on product fatigue life. Despite daunting challenges in applying classical fatigue principles to describe crack nucleation and growth, our numerical simulations provided valuable insights, capturing the trend of observed crack paths, albeit not their velocity. This research sheds light on the complex interplay between residual stresses and crack propagation, offering important considerations for fatigue analysis and product design.

Two methods of durability prediction of fillet welds were researched in this study. Namely, the structural Hot-Spot method and the structural stress method fe-safe Verity were applied to fatigue life estimation of a double plate lap fillet weld made of high-strength complex phase CP-W800 steel. Durability predictions were compared against available high-cycle fatigue experimental data obtained for the same weld detail and material. Both 2D and 3D finite element meshes were considered in the simulations. It was shown that comparable predictions were obtained using either the Hot-Spot method or the fe-safe Verity module in the case of the 3D FE mesh. On the contrary, a less conservative durability prediction was observed using the Hot-Spot method and a more conservative durability prediction was gained using the fe-safe Verity module in the case of the 2D FE mesh due to a different consideration of stress concentration around the weld.