ESTIMATION OF THE EQUATION PARAMETERS OF THE ELASTOPLASTIC STATE OF THE MATERIAL BY THE RESULTS OF INSTRUMENTAL INDENTING
Abstract
This paper discusses the possibility of determining the coefficients of the equation of state describing the elastoplastic behavior of the material under study by comparing experimental data with model calculations. The applied method of instrumental indentation, by introducing additional techniques, allows one to obtain not only hardness and elastic modulus, but also additional information about the dependence of these values on the immersion depth of the indenter, as well as about the viscoelastic properties of the test material. The study was carried out using an upgraded NanoScan-4D nanohardness tester equipped with a sapphire spherical indenter. The shape of the indenter was obtained by scanning with an atomic force microscope. The need to work with minimal loads and maximum lateral resolution, which is required for studying structured materials, led to the need to use the NanoScan-4D nanoindentation module and an indenter with a radius of curvature less than 20 μm. The results of measurements for a spherical indenter in the study of materials with various types of chemical bonds are presented. In addition to metal samples (steel, aluminum, aluminum alloys D16 and AMg6), polycarbonate and fused silica samples were measured. The data obtained indicate the linear character of the sigma-epsilon curve for the studied materials. Based on the analysis of the data obtained, it is concluded that this kind of research is promising and that the results of instrumental indentation are informative in terms of obtaining information on the parameters of the elastoplastic behavior of the test material. An important direction of further research, expanding the possibilities of obtaining additional information on elastoplastic properties, is the development of a technique for obtaining reliable information on the sigma-epsilon diagram when indenting crystalline materials with indenters with different apex angles.
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