Estimation of mechanical characteristics of salt rock crystals based on the mathematical model of nanoindentation using scanning probe microscope Dimension Icon

The scanning probe microscope Dimension Icon is used both to assess the relief of the sample surface and to obtain the force response of the sample during the interaction of the cantilever (indenter of special shape, located at the end of the elastic console) with the sample surface. At the same time, unlike other devices, such as NanoTest-600, where as a result of indentation the researcher receives the value of hardness and effective modulus of elasticity with the help of software connected with this device. Dimension Icon gives only the dependence of indenter deviation on the displacement of the cantilever base. For the known flexural stiffness of the elastic console, one can determine the force-displacement curve during loading and unloading. Then here comes the problem of interpretation of this curve: how can we evaluate the mechanical characteristics of the material on its basis? The answer to this question particularly depends on the character of the mechanical behavior of the material. We consider the two-dimensional axisymmetric problem of sample indentation at the stages of loading and unloading for the range of indentation depths significantly exceeding the head spherical part of the cantilever probe, under the assumption of elastic-perfectly-plastic material model. Numerical simulation is carried out in the ANSYS package within the framework of the contact problem, under the assumption of an absolutely rigid cantilever tip. We propose the method for estimating the yield stress and the modulus of elasticity of the sample surface layers and determine the values of mechanical characteristics for several salt rock crystals by processing the results of the computational experiment and the data of previous experiments.