The stress-life fatigue behaviour of aluminium alloy foams

The tension-tension and compression-compression nominal stress versus fatig ue life responses of Alulight closed cell aluminium alloy foams have been m easured for the compositions Al-1Mg-0.6Si and Al-1Mg-10Si (wt%), and for re lative densities in the range 0.1-0.4. The fatigue strength of each foam in creases with the relative density and with the mean applied stress, and is greater for the transverse orientation than for the longitudinal orientatio n Under both tension-tension and compression-compression loading the domina nt cyclic deformation mode appears to be material ratchetting; consequently , the fatigue life is highly sensitive to the magnitude of the applied stre ss. A micromechanical model is given to predict the dependence of life upon stress level and relative density. Panels containing a central hole were f ound to be notch insensitive for both tension-tension and compression-compr ession fatigue loading: the net-section strength equals the unnotched stren gth.