Simulation of Cellular Aluminium: Crash and Impact

摘要

The present paper highlights results from the priority program "Cellular Metals" of the Deutsche Forschungsgemeinschaft (DFG SPP 1075). The crash and impact behaviour of cellular aluminium is investigated numerically and experimentally. The simulations are conducted mesomechanically, i. e. the porous structure of the foam is discretised explicitly. In case of a crash — velocities about 10 m/s - the metal foam is plastically deformed absorbing the kinetic energy of a macroscopic impactor. Having an impact as known from space applications - velocities up to 10 km/s and more - small material particles hit single cell walls and cause fragmentation and phase transitions on the mesoscopic scale. Therefore, different numerical techniques have to be used for crash and impact. In order to obtain the plastic characteristics of the foam, representative volume elements are gained from computer tomographic images and discretised with finite elements. The discretisations together with a material model for the cell walls are loaded multiaxially to obtain yield, hardening and flow rule properties. For the numerical simulation of the impact the foam is discretised with an artificial finite element mesh. The discretisation features the basic structural properties of the real foam, e. g. average cell size and thickness of cell walls. Impacts on real shield configurations are simulated and compared to experiments. After this validation the shield will be optimised by parameter variations in the simulation in future studies.