Material characterization and modeling of textured aluminum alloys used in a bumper system

Abstract

In the present paper, two materials AA7108 and AA6060, which can be parts of a typical bumper system in aluminum, have been characterized. Material properties were identified for a material model that was recently implemented in LS-DYNA, through material tests. These included both quasi-static and dynamic tensile tests. The model consists of isotropic elasticity, the anisotropic yield criterion Yld89 of Barlat and Lian, associated flow rule, combined non-linear isotropic and kinematic strain hardening, and strain-rate hardening. Additionally, a fracture criterion based on critical thickness strain has been implemented in the model. For AA7108, both the soft W-temper and temper T6 were studied, while only temper T1 for AA6060 was investigated. It was found that the yield surfaces for the two tempers in AA7108 were almost identical. The yield surfaces of the two investigated alloys are quite different because the materials have different texture. An automated procedure developed to predict forming limits with LS-DYNA called an FLD-calculator was applied to generate Forming Limit Diagrams and Fracture Forming Limit Diagrams for the materials. For AA7108, fracture was initiated before or simultaneously to plastic instability, while for AA6060 plastic instability always took place before fracture