Prediction and prevention of fracture defect in plastic forming for aluminum foam sandwich panel

Abstract

In this study, the predicting and avoiding method of core fracture in plastic forming for aluminum foam sandwich panel (AFSP) were investigated. By observing the macroscopic core cracks and microscopic morphology of the fracture surfaces, the core fracture occurred in plastic forming of AFSP can be confirmed as ductile fracture. Five ductile fracture criteria were introduced for predicting the fracture initiation and detailed simulations on plastic forming of AFSP were performed with a mesoscopic 3D Voronoi AFSP model; besides, multi-point forming experiments of cylindrical, spherical, and saddle-shaped AFSPs were carried out. Normalized value I distributions on the cores using different fracture criteria and core cracks found experimentally indicate that Ko fracture criterion is the most suitable to predict the core cracking during curved AFSPs forming. Moreover, on the basis of the core value I distributions obtained using Ko criterion and the experimental panels in the case of different forming step numbers and core relative densities, it is found that the risk of core fracture can be reduced by adopting multi-step forming and increasing the core relative density.