A new variable speed phase transformation constitutive model of shape memory alloys

Abstract

Due to their unique shape memory effect, superelastic effect, as well as the excellent physical and chemical properties and biocompatibility, shape memory alloys (SMAs) have been widely used in aerospace, weapons and industrial automation. It is of great engineering significance and academic value to establish a constitutive model for accurately and effectively describing the thermomechanical behavior of SMAs. In this paper, a concept of crystal variable speed coefficient is introduced. A new variable speed constitutive model of SMAs considering rate distribution of SMA phase transformation is proposed. In order to verify the accuracy of the constitutive model proposed in this work, thermomechanical properties of the SMA wire were tested experimentally first, and both a new method for obtaining the starting and ending points of phase transformations and the conventional method have been used in this process. Then, numerical simulations were performed by using the variable speed constitutive model and the conventional Brinson model, respectively. The results were compared which indicates that the variable speed model is in better agreement with the experimental data. Therefore, the proposed model in this paper can predict the thermomechanical response of SMAs more accurately and effectively.