Ductile fracture of AA6111 alloy including the effect of bake-hardening

The thermal cycle of paint baking for auto bodies alters the mechanical properties of aluminum alloys including, possibly, their fracture behavior. In this study, the plasticity and fracture of AA6111 sheet after a 30 min heating cycle at 180 °C is investigated. Uniaxial tension, plane-strain tension and disk compression experiments are performed to assess the plasticity of the material. The results are used to calibrate Yld20004-18p anisotropic yield function. An evolution of the yield locus with plastic deformation is observed. This is represented by evolving the exponent of the yield function, rather than the coefficients themselves. The post-necking hardening curve is identified by numerically simulating a notched-tensile test. The fracture locus is probed using notched-tension, center-hole, and shear experiments. In every case, digital image correlation (DIC) is used to acquire the surface strain fields. In parallel, finite element simulations of the fracture specimens are used to approximate the fracture strains, triaxiality, and Lode angle parameter. Yld2004-18p model shows good overall agreement with the experiments; thus, the fracture locus is probed with this model.