Effect of the large cells on the fatigue properties of closed-cell aluminum alloy foam

The effect of the large cells on the fatigue properties of closed-cell aluminum alloy foam is studied experimentally and numerically. To do this, a parameter termed as characteristic diameter (Dch) is introduced. 44 dog-bone type specimens are tested with MTS fatigue test machine. In addition, the fatigue performances are numerically simulated by using foam models generated with a program given in this paper. In both cases, large scatter in fatigue life is observed. After classifying the foams into different groups based on their Dch, the fatigue life results of foams within the same Dch range show smaller diversity. It indicates that Dch is an effective parameter which can be used to classify the fatigue performance of foam materials. For foams with same relative density, foams with higher Dch are inclined to have shorter fatigue lives, even though the cell size distributions of foams are different. It is concluded that the fatigue life of foam is dominated by the large cells rather than the cell size distribution. By observing the fatigue life contour obtained from numerical simulation, the dangerous regions in the cell structure are found near the cell walls of larger cells and on the outer surfaces of foam.