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

The tension-tension and compression-compression cyclic properties are measu red 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 b oth monotonic and fatigue tests. In contrast, the Alporas foam is more irre gular in microstructure, and exhibits crush-band formation at random locati ons under uniaxial compression; in compression-compression fatigue, a singl e crush band forms and broadens with additional fatigue cycles. Progressive shortening of the specimen in compression-compression fatigue, and progres sive lengthening in tension-tension fatigue are due to a combination of low cycle fatigue failure and cyclic ratchetting. S-N fatigue curves are prese nted 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. (C) 1999 Acta Metallurgica Inc. Publish ed by Elsevier Science Ltd All rights reserved.