Engineering approach for modeling the deformation and fracture behavior of thin welds

Structural components made of thin tailor-welded blanks (TWB) are essential for the design of modern lightweight car bodies. Investigating the formability of these blanks requires detailed information about the mechanical behavior of the welds. Therefore, this study presents an engineering approach that combines experimental and numerical methods for determining elastoplastic properties and fracture parameters of thin aluminum alloy welds produced by gas metal arc (GMA) welding. This approach considers the entire weld seam including surface features as well as inhomogeneous grain structures in as-welded condition, as these features may considerably influence the actual mechanical behavior. Single-pass welds of aluminum alloys AA-5087 and AA-5554 were deposited on a 1.2 mm-thick sheet of aluminum alloy EN AW-5182 using the Cold Metal Transfer (CMT) welding process. Tensile samples consisting almost exclusively of the weld metal were prepared. The three-dimensional (3D) geometries of these samples were captured using an optical scanner. Initial flow curves describing the plastic deformation behavior of the weld were calculated based on the force-elongation curves obtained from tensile testing of the samples. These flow curves and the meshed 3D geometries of the welds were employed for building numerical models of the tensile testing procedure. The flow curves and the fracture locus were iteratively optimized until the force-elongation curves calculated in the simulations and measured in the tensile tests matched each other. The elastoplastic properties and the fracture parameters can be applied for modeling aluminum welds in forming simulations of tailor-welded blanks consisting of, e.g., aluminum alloys and steels.