Superelastic Behavior under Cyclic Loading for TiNi Shape Memory Alloy Bars

The mechanical properties of TiNi shape memory alloy bar were investigated using loading-unloading cycling tests under quasi-static conditions.The Phase transformation stress,deformation module,residual strain,dissipated energy and so on are considered as superelastic characteristic parameters of these specimens.The changes of these parameters with cyclic number were analyzed.Results indicate that at the beginning stage of loading cycling,these parameters considerably decrease with the increase of cyclic loading number.After certain cyclic numbers(as emax=5%,the number of cyclic loading may approximately be 10;as emax=2%,the number of cyclic loading may approximately be 15),the value of these parameters tends to be steady.In other words,after loading-unloading cycling training,the initially pseudoelatic TiNi shape memory alloy bar can obviously present complete superelasticity,thus,the mechanical property parameters of this alloy tend to be steady.In order to apply this alloy bars to practice,the influence of cyclic loading on alloy superelasticity should be considered,and the appropriate design should be proposed based on practical condition.