Análise por elementos finitos do comportamento de Tailor Welded Blanks (TWB) submetidos ao ensaio de tração uniaxial

Abstract

The Tailor Welded Blank (TWB) manufacturing process consists of joining two or more sheets with different specifications (materials, thicknesses, coatings, and other physical and/or chemical properties), subjected to forming, resulting in mass and mechanical strength optimization, achieving the "right material in the right place." Numerical simulation using the finite element method is employed to predict the body's behavior and presents an additional challenge when dealing with TWB, which is the welded joint. Typically, sheet modeling is performed without considering the weld to simplify complexity and reduce computational processing. Laser welding creates narrow melted (MZ) and heat-affected (HAZ) zones, making it difficult to extract tensile test specimens for evaluating the mechanical properties of the welded joint, thus, some experimental approaches such as the Rule of Mixtures (ROM) and the use of reduced-size specimens (sub-size) emerge for characterizing this region. This study aimed to establish a correlation between the results of experimental tensile tests and numerical simulations on TWBs with different weld line orientations. Using Abaqus® software, the properties of the weld line obtained by ROM were considered. The TWB used is composed of two different interstitial-free steels, joining three distinct zones (two base materials and the welded joint). The mechanical properties of the elastic and plastic regimes of the tensile test were considered in the representation. The results indicated that the presence of the weld affects the results, altering the shear load with the variation of the inclination relative to the rolling direction. Fracture tends to occur in the material with lower mechanical strength, and the welded region acts as a stress concentrator, altering the fracture direction of the TWB under tensile stress. ROM proved to be effective in representing the weld, and the numerical model, simplified as isotropic, obtained coherent results concerning the breaking load and elongation for weld line inclination angles of 0°, 45°, and 90°, being the model not representative for intermediate angles (15°, 30°, 60°, and 75°) that strongly depend on anisotropy.