Modeling of the electrical resistance of shape memory alloy wires

The strain sensing principle of shape memory alloy (SMA) based on its electrical resistance (ER) value is analyzed in this paper. A mathematical model to describe this principle is developed based on the relationship between the electrical resistivity and the martensite fraction of an SMA wire. The proposed model can be used at different temperatures and different initial conditions. To verify the validity of the proposed model, various experiments were conducted. The numerical results based on the proposed model agree well with experimental results, indicating that an SMA wire with a proper model can be utilized as a sensing element.