Fatigue failure of an open cell and a closed cell aluminium alloy foam

Abstract

The tension–tension and compression–compression cyclic properties are measured for an open cell “Duocel” foam of composition Al 6101–T6, and a closed cell “Alporas” foam of composition Al–5Ca–3Ti (wt%). The Duocel foam has a relatively uniform microstructure, and undergoes homogeneous straining in both monotonic and fatigue tests. In contrast, the Alporas foam is more irregular in microstructure, and exhibits crush-band formation at random locations under uniaxial compression; in compression–compression fatigue, a single crush band forms and broadens with additional fatigue cycles. Progressive shortening of the specimen in compression–compression fatigue, and progressive lengthening in tension–tension fatigue are due to a combination of low cycle fatigue failure and cyclic ratchetting. S– N fatigue curves are presented for the onset of progressive shortening in the compression tests, and material separation in the tension tests; it is envisaged that such curves will be of practical use in design.