Phase transformation may occur in shape memory alloys (SMAs) by variations in stress and temperature. The transformation changes the mechanical properties of these alloys, e.g. Young modulus. Due to the high sensitivity of these alloys to temperature, ambient temperature is so important. For instance, at a constant value of stress, the value of strain alters by variation in ambient temperature. Additionally, shape memory alloys show different behavior by variation in applied stress at a constant temperature. The strength of the alloy is also dependant on the exsiting phases in the material. Deformation and stress occur at asperity in local contact. Since shape memory alloys are practically in contact with other homogeneous and heterogeneous materials, investigation of contact in these alloys are essential. For studying contact in SMAs, a model should be developed which can consider properties of each material point since stress variation affects material properties of these alloys. Moreover, different behaviors are seen in loading and unloading cycles. To the authors’ knowledge, there is no suitable model which can model contact in shape memory alloys. Therefore, a new method was proposed in which the material properties are the function of time and position. The proposed model was verified and validated by experimental tests. The results show that the model can predict the experimental results with a reasonable accuracy. The constitutive equations are based on the relation between stress and strain, but the contact relations are based on force and displacement. Consequently, a representative strain was defined based on the elastic response of the material since the constitutive equations of shape memory alloys and contact relations are not consistent. Finally, the new method was extended for shape memory alloys and verified with experimental results. The outcomes are decent as the first study in the modeling of contact in shape memory alloys. Keywords: Shape Memory Alloys, Contact Mechanics, Asperity, GW Model, Representative Strain, Indentation Testing
