GENERATION OF RECOVERY STRESSES - THERMODYNAMIC MODELING AND EXPERIMENTAL-VERIFICATION

Shape memory elements generate significant recovery stresses when the shape recovery associated with the reverse martensitic transformation is impeded during heating. This process of stress generation is influe nced by many parameters. A fundamental model has been developed to des cribe this generation of recovery stresses. The model is based on a ge neralised thermodynamic analysis of shape memory behaviour. The mathem atical approach and the assumptions in this model are selected in such a way that the calculations yield close approximations of the real be haviour and that the final mathematical equations are relatively simpl e. The paper presents also experimental measurements of recovery stres s generation for complex restraining conditions. Comparison of the exp erimental results with the calculated results confirm that this model can be used to predict quantitatively the generation of recovery stres ses.