Phase transitions of shape memory alloys in soft and hard loading devices

Shape memory alloys exhibit a complex load deformation temperature behaviour (especially e.g. hysteresis and 'inner' loops) which is due to the occurence of a first order phase transition. By load deformation diagrams the socalled shape memory effect can be made visible. We study a model of I. Mueller et al., based on statistical mechanics, which is applicable to biaxial loading of polycrystalline bodies and incorporates the rotational part of a deformation. Recently, I. Mueller et al. have proposed a second model incorporating the coherence energy for solid phase mixtures. For two principle variants of experiments (soft and hard loading devices) we present numerical simulations of load deformation curves for either of the two models. Comparing these with experimental results of so-called 'inner loops' in a hystersis the second model shows its superiority. (orig.)Available from TIB Hannover: RR 5549(251)+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman