Resumen de Anisotropic rate-dependent plasticity and fracture of AA5754
Joseba Mendiguren Olaeta, Borja Erice Echávarri
The effect of the anisotropy, the loading rate and stress state on the ductile fracture of AA5754 cold-rolled sheets is investigated. First, the quasi-static plasticity behaviour is analysed experimentally testing biaxial and uniaxial tensile specimens electro-discharge machined at several orientations with respect to the rolling direction. These experiments are then used to calibrate a three-dimensional version of the Yld2000 yield criterion [1]. The strain rate dependency of the material is evaluated testing notched tension specimens tested at different loading rates. The resulting force-displacement curves, showing negative strain rate sensitivity, are employed to calibrate the work hardening constants of a modified isotropic Johnson-Cook-type law [2] through inverse modelling with finite element modelling. FE simulations of the experiments on central hole, notched, shear and biaxial specimens conducted at several loading rates and orientations with respect to de rolling direction, monitored with three-dimensional digital image correlation, are performed to obtain the Cauchy stress and equivalent plastic strain histories from the critical elements located where fracture is observed in such experiments. The anisotropic stress state, given as by the Cauchy stress tensor normalised with the equivalent von Mises stress, is analysed for each case extracting the so-called loading paths to fracture from the afore-mentioned histories. Lastly, these are graphically visualised in two-dimensional polar plots constructed by projecting such paths onto planes defined by normalised stress components.
