Pseudoelastic Behaviour of TiNi Shape Memory Alloy Subjected to Strain Variations

The pseudoelastic behaviour associated with the martensitic transformation (MT) of TiNi shape memory alloys subjected to strain variations has been investigated experimentally. The results are summarized as follows. Firstly, with respect to strain variations within the MT region: (1) The reverse transformation stress does not depend on the maximum strain. (2) The MT stress and reverse transformation stress decrease with an increase in the number of deformation cycles. (3) The rate of variation in both transformation stresses with cycling decreases with the increase in the number of cycles. Secondly, with respect to strain variations beyond the completion points of MT and reverse transformation: (1) At the start points of MT and of the reverse transformation, over shooting of both transformation stresses appears. (2) The higher the temperature and the larger the maximum strain, the larger the overshoot of both transformation stresses and the larger the decrease of the reverse transformation stress.