Mechanical behaviour and strain rate sensitivity analysis of TA2 by the small punch test

In this study, small punch tests are conducted at various displacement rates (0.005-0.5 mm/min) to investigate the mechanical behaviour and strain rate sensitivity of commercial pure titanium TA2. The experimental results show that the yield load P-y and the maximum load P-max depend strongly on the displacement rate. An exponential function is established to describe the relationship between the material properties and the displacement rate. In order to describe the deformation characteristics of the specimen in the small punch tests at different strain rates, the Johnson-Cook constitutive model is applied in the finite element simulation. The influence of the constitutive parameters on the deformation behaviour is also analysed. The results indicate that the elastic bending region and plastic bending region are mainly affected by parameter A, whereas parameter B dominates the membrane stretching region and the plastic instability region of the curve. An improved inverse algorithm, combining the advance-and-retreat method with the golden section search method, is proposed. Based on characteristic analysis of the parameters, the one-dimensional and two-dimensional identification methods are used to identify the constitutive parameters from the load-displacement curve. Thus, the mechanical properties of materials can be calculated by inversion of the constitutive parameters.