SHAPE-MEMORY EFFECTS UNDER COMBINED FORCES

Thin wall tubes made of CuAlZnMn shape memory alloy were subjected to combined axial and torsional loads in low temperature martensite state . The strain recovery accompanying the reverse martensitic transformat ion upon heating-shape memory effect-was studied. The stress free reco very proceeded by the simultaneous reversion of all induced strains, i .e. the strain path followed the shortest linear trajectory towards th e origin of the strain space. When, however, a bias external stress wa s applied upon the reverse martensitic transformation, the response of the heated tube became remarkably non-linear. The effect was explaine d on the basis of the interaction of the bias stress with martensite v ariant particles induced in various stages of the complex deformation history. (C) 1997 Elsevier Science S.A.