In situ shear behavior of open-cell austenitic 316L steel foams

Foam cores in crash boxes are subjected to large shear forces during crash situations. Here, the failure behavior of 316L open-cell stainless steel foams under shearing conditions was investigated. A custom-made grip system was used to conduct in situ experiments with a scanning electron microscope and a digital light microscope. A foam model was created based on mu-CT data and imported into FE software for simulation of the shearing test. Furthermore, the shear-induced strain fields were evaluated using digital image correlation. On the mesoscale, the foam cells mainly experienced torsion, while on the microscale, the foam struts failed due to tensile and bending loading. Twisted cells became almost parallel to the loading direction, leading to the tensile loading of the foam struts. Many slip lines developed on the strut walls, revealing that the steel struts underwent ductile fracture. In conclusion, the failure behavior of the foam struts and cells was greatly influenced by the loading conditions of the foams.