Tensile failure analysis of laser stake-welded T-joints: X-ray tomography based conformal finite element and fractal theoretical approaches

Abstract

To promote the application of complex structural materials in large size, the interfacial joint is the key component for sandwich structure to wipe off the sample size limitation and fabricate multi-material structures. However, the laser welding process inevitably induced void defects in the welded joint, influencing the mechanical properties of the whole structure. In this paper, the aluminum alloy laser stake-welded T-joints were fabricated in a laser welding system. The geometric deviations and internal void defects of T-joints were visualized and quantified by micro X-ray computed tomography (μCT). Two image-based finite element models were reconstructed from CT images to discuss the effect of different manufacturing-induced defects on the tensile behaviour of T-joints. The geometric deviations of T-joints make a response for the decrease of strength and the void defects result in the decrease of Young’s modulus of T-joints. The fractal dimension theory, based on the value of void volume and the distance of the void to the interface obtained from CT images, was developed to predict the strength of the T-joint. The results matched well with the experimental results.