Shape Memory Effect and Hysteresis Behavior of Shape Memory Alloy Metal Rubber

The present work focuses on the shaping craft of shape memory alloy metal rubber (SMAMR) and its temperature dependent mechanical properties. Heat treatment process was conducted to form a stable SMAMR sample beyond the general procedure of metal rubber (MR) in order to resist the shape memory effect (SME). The influence of the heat treatment procedure on the mechanical properties was tested. The quasi-static experimental investigations were carried out to obtain the storage modulus and energy loss factor varying with the structural parameter, strain amplitude, and material temperature. It is found from the experiment results that the SMAMR sample which underwent the heat treatment was able to remember its original moulding shape and recover from the overloading plastic deformation when heated above the phase transition temperature. For comparison, another sample without the heat treatment was heated to the same temperature after the plastic deformation, but the final shape deviated from the original one. It is also confirmed that the heat treatment procedure obviously increased the storage modulus and loss factor of SMAMR. Just like the variety elastic modulus of shape memory alloy (SMA), the storage modulus of SMAMR increased obviously while the material was heated above the phase transformation temperature due to the elastic modulus change of SMA wire. The quasi-static experiments showed a hysteretic property of the stress–strain curve in a certain temperature. But the hysteretic curve was temperature and structural parameter dependent. It is concluded that the heat treatment process is necessary to obtain a stable SMAMR during the phase transformation. The varying storage modulus and superior loss factor performances of SMAMR make itself a kind of attractive functional material which will be available in the active suppression of vibration. For example, it can be fabricated to a rotor bearing with changeable stiffness and damping, which is of practical significance in the active control of synchronous vibration of rotors crossing resonance condition.