Tensile and Shear Element Erosion in Metal Foams

The goal of this paper is to simulate fracture observed in tensile and shear tests of steel foam specimens. Deshpande-Fleck plasticity was employed for numerical modeling, and calibrated against compressive and tensile experiments. Steel foam has plastic yield stress, and can deform under compressive load beyond 60% engineering strain. Unlike in compression, steel foam fractures at a small strain in tension. Weak tensile behavior is captured with the element deletion. In order to enhance the realism of the simulated fracture patterns, yield stress, Young modulus, and failure strain were randomly varied between all elements. Unfortunately, default material erosion produced shear fracture patterns significantly different from the experiments. Thus, alternative element erosion was postulated, and it was based on the maximum principal strain. The proposed criterion was shown to give adequate agreement with the experimental results. Tensile and shear fracture modeling of steel foams may benefit from inclusion of spatial variability of material properties. The proposed principal strain based element erosion performed better than the principal stress fracture cut-off.