Abstract: Indentation tests of the closed-cell aluminum foam under the flat-end cylindrical indenter are performed.Effects of indenter diameter and relative density of aluminum foam on the indentation response,indentation hardness,energy absorbing capability and energy absorbing efficiency were investigated.Indentation test results were compared with the results of uniaxial compression tests.The results show that the response in the case of flat-ended punch indentation was similar to that observed in uniaxial compression,but indentation strength was higher than that observed in uniaxial compression.The deformation of aluminum foam was confined only to the region directly under the indenter with very little lateral spread,and the indentation deformation was local and non-uniform.The tear energy and energy absorbing efficiency of aluminum foam was not related with the indenter diameter and relative density of aluminum foam.The indentation hardness linearly decreased with the increase of indenter diameter and the decrease of relative density,but the energy absorbing capability linearly increased with the increase of indenter diameter and the increase of relative density.At a certain indentation depth range,the difference between rigid foundation and simply supported boundary conditions on the indentation response of aluminum foam could be ignored.