CHANGES OF ELASTIC-CONSTANTS ASSOCIATED WITH FATIGUE DAMAGE IN AN ALUMINUM-ALLOY

Dynamic modulus and contraction ratio changes have been measured following fatigue cycling using a resonance technique on a high strength aluminium alloy. It is shown that the classical hardening behaviour is accompanied by a decrease in dynamic modulus. The contraction ratio increases in the beginning followed by a sharp decrease. The consequences of the measured changes in the elastic constants are evaluated for the elastic strain field near a crack tip. It is shown here that the size of the isodeformation profiles can be significantly modified in plane strain conditions, if the altered values of the elastic constants are taken into account.