Pseudo-Elastic Behavior of NiTi SMA under the Quasi-Static and the Impact Cyclic Tests

Abstract

Abstract. To characterize the thermomechanical cyclic response, especially Pseudo-elastic behavior of NiTi shape-memory alloy (SMA) at different temperatures and different loading frequencies, a series of tests of both quasi-static and dynamic uniaxial compression cyclic loading have been performed on cylindrical samples, using an Instron servohydraulic testing machine and the Hopkinson technique. Transformation temperature, after dynamic loading is measured and compared with that of as-received state. The influence of the annealing temperature on the fatigue response is also examined. A few noteworthy conclusions are as follows: (1) Transformation temperature, can be changed under higher strain rates; (2) By changing the annealing temperature, the transformation stress and the dissipated energy of NiTi can also be obviously changed, so as it changes the transformation temperature, Af ;(3) In cyclic loading, the dissipated energy over cycles tends to be a minimum stable value, and it seems that cyclic loading leads to a stable Pseudo-elastic behavior of the alloy; (4) Repeated impact tests of the alloy produce slightly changes in the shape of the Pseudo-elastic loop and in the dissipated energy comparing with the quasi-static cyclic tests.