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Weld fatigue evaluation using the mesh-insensitive Battelle structural stress method has been applied to fusion welds, resistance spot welds and non-welded components. The effectiveness of the Battelle structural stress procedure has been demonstrated in a series of earlier publications for welded structures with different joint types, plate thicknesses, and loading modes. In this paper, a weld fatigue evaluation procedure using the Battelle structural stress method is proposed for friction stir welds currently being used in the automotive and aerospace industries. The applicability of the Battelle structural stress procedure is demonstrated by comparing fatigue life predictions for friction stir welded specimens to well-documented test data from the literature. Different specimen types, plate thicknesses and loading ratios were analyzed for several aluminum alloys.

In this paper, the applicability of the finite element-based, mesh insensitive Battelle structural stress method is demonstrated for fatigue life predictions of notched specimens (non-welded) with different specimen types, and notch shapes. Well-documented notch fatigue data were analyzed using the Battelle structural stress fatigue evaluation procedure, including notched plate fatigue data for steel and aluminum alloys. The effectiveness of the Battelle structural stress procedure has been demonstrated in a series of earlier publications for welded structures with different joint types, plate thicknesses, and loading modes. Here, a similar Battelle structural stress procedure suitable for finite element modeling and service life simulations is proposed for structures with notches. Unlike weld fatigue data, the crack propagation portion of the fatigue life associated with a notch does not always dominant the total number of cycles to failure.

In this paper, the Battelle structural stress method for evaluating the fatigue life of welded joints is applied to weld-bonded joints. In order to overcome the complexity of modeling and analyzing both crack paths in weld-bonded joints, a superposition approach is proposed as a reasonable and effective alternative for fatigue design purpose. The superposition approach for evaluating the fatigue life of weld-bonded joints uses two simplified finite element (FE) models: a spot weld model and an adhesive bond model. Each simplified FE model is required to represent the fatigue behavior properly and to minimize the modeling effort without sacrificing the accuracy of the results. The superposition concept can be used in practice if the life evaluation results using the superposition are comparable with the experiments. For the spot welds, the recently developed simplified procedure and master fatigue S-N curve is employed [1].

Tailor-welded blanks (TWB) have been increasingly used in the automotive industry as an effective way to reduce weight and costs. Although some of the joining processes for TWB are relatively well known, little independent information exists regarding welding procedure effects on weld/HAZ properties, particularly their effects on form-ability and structural performance under various conditions. In this paper, advanced computational modeling techniques were used to investigate the effects of welding procedures on weld property evolution and its impact on the formability issues. Two case studies were presented. One is on TIG welding of 6000 series aluminum tailored blanks, where thermomechanical effects on weldability was analyzed. Its implication on weld performance during forming will be discussed. The other case is on laser-beam welding of high strength steel to mild steel with a non-linear weld. The detailed thermal history and residual stress development will be presented.

As the automotive industry seeks to remove weight from vehicle chasses to meet increased fuel economy standards, it is increasingly turning to composites and aluminum. In spite of increasing demands for quality aluminum alloy spot welds that enable more fuel efficient automobiles, fatigue evaluation procedures for such welds are not well-established. This article discusses the results of an evaluation Battelle performed of the fatigue characteristics of aluminum alloy spot welds based on experimental data and observations from the literature. In comparison with spot welds in steel alloys, aluminum alloy spot welds exhibit several significant differences including a different hardness distribution at and around the weld, different fatigue failure modes, and more. The effectiveness and applicability of the Battelle structural stress-based simplified procedure for modeling and simulating automotive spot welds has previously been demonstrated by Battelle investigations.