Compression fatigue of a cellular Al alloy

The cyclic compression of a cellular Al alloy has been evaluated. Plastic compression occurs beyond a critical number of cycles, NT. At N<NT the cumulative strains are negligible and the material has cyclic stability. At N>NT, strain accumulates rapidly and preferentially within deformation bands, until the densification strain has been reached. The bands form preferentially from large cells in the ensemble. Such cells develop plastically buckled membranes which experience large strains upon further cycling, which lead to cracks. The cracks, once formed, result in rapid cyclic straining. This feature controls the fatigue life.