The simulation of metal foams forming processes

Metal foams are two-phase compounds of a gas and a solid with several interesting physical and mechanical properties; in particular they have very low density, good rigidity, excellent energy absorption, high vibration damping. At now, the final shape of foamed devices is directly obtained through the foaming process itself and no further shaping steps are expected. Anyway, the plastic formability of metal foams, in order to both characterize the material itself and to produce more complex parts, seems to be useful for several industrial applications. Since metal foams are quite new products, the basic aspects ruling plastic deformation processes are still partially unknown and FEM methods may represent a valid tool for deepening these topics. This work deals with the formability of Aluminum Foam Sandwich (AFS) panels and it is focused on the FEM simulation of a compression processes. A numerical model was set up by using the FEM code Deform 2D v10.1. Foam behaviour was simulated by means of a compressible (porous) material model and the foam cracking was simulated using a damage model based on the foam density parameter. Some FEM routines were implemented into the FEM code to take into account both the non-homogeneous distribution and the strain hardening effect of the foam cells. An experimental campaign based on the compression of AFS panels made of close cells foam was carried out to fine tune and to validate the model. In particular, experimental data regarding load stroke curves and foam density were used to optimize the material description. An innovative solution, based on a non-linear relation between foam density and effective strain of the foam, was implemented into the FEM code.