Mechanics examination on the wear behaviour of shape memory alloys

Abstract

Shape memory alloys are well recognized functional and smart materials, which have been exploited to develop intelligent structures and devices in many fields. Of particular importance is its exciting application in the field of biomechanical engineering. In addition, further potential applications of shape memory alloys are being investigated, such as shape memory alloys-based functional composites. Recent experimental research indicates that shape memory alloy nickeltitanium alloy (NiTi) is superior to stainless steel against wear and could be applied in tribological engineering. It is believed that the super wear resistance of shape memory alloys is mainly due to the recovery of the superelastic deformation. Our recent wear study indicates that wear rate is very sensitive to the maximum contact pressure. In the present study, which involves applying Hertz contact theory and the finite element method, the wear behavior of shape memory alloys is investigated through analyzing the contact pressure. In contrast to the existing explanation of the major contribution of superelasticity, our investigation indicates that the superior wear resistance of shape memory alloys is directly linked to the low Young's modulus of the alloy, the low transformation stress and large transformation strain, which result in low maximum contact pressure and therefore low wear rate. Additionally, high plastic yield strength of transformed martensite NiTi also enhances its wear resistance.