Effect of Material Parameters on the Indentation Mechanical Behavior of Superelastic NiTi Shape Memory Alloy

Owing to the unique superelasticity of shape memory alloys (SMAs), the development of a theoretical model of its contact mechanics proves a challenge. This study compares and investigates the influence of superelastic material parameters on the uniaxial and nanoindentation behavior of a NiTi SMA based on the constitutive model and finite element simulation using the controlled variable method. The elastic modulus and phase transformation strain is found to influence the entire indentation process: The initial stress due to phase transformation when loading primarily affects the loading stage of the indentation curve and the starting stress of reverse phase transformation only affects the unloading stage. The superelastic modulus and Poisson's ratio have a negligible effect on the indentation behavior. Furthermore, the variation law and influence of superelastic material parameters of the NiTi SMA on its indentation behavior is systematically analyzed using an orthogonal design method. The results demonstrate that the elastic modulus and phase transformation strain significantly influence the maximum indentation force and indentation loss work, whereas the other superelastic material parameters have a negligible effect. The maximum indentation force is proportional to the elastic modulus and inversely proportional to the phase transformation strain, and the dissipated energy is proportional to the elastic modulus and the phase transformation strain. Moreover, the dissipated indentation energy decreases with an increase in the maximum indentation force. This study can guide the development of contact mechanics models for superelastic SMAs.