Quantitative Evaluation of Stress-Strain Curves by Spherical-Tip Nanoindentation with Variable Radius Method

概要

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We propose a novel evaluation method to obtain precise stress-strain curves by spherical-tip nanoindentation with continuous multiple loading technique. The small-sized spherical-tip indenters have an imperfect shape and it causes miss-fitting with tensile test result. We adopted the variable radius method, where we defined the precise indenter radius as the function of contact depth to calculate the stress-strain response precisely. We calculated the representative stress and representative strain by combining Hollomon's law, Hill's model, proper strain model, and the variable radius and compared with the tensile test result. It is found that stress-strain curves obtained by using the variable radius method agree well with the tensile test result rather than using nominal radius. These results clearly indicate the effectiveness of our method to evaluate the stress-strain response by using the small-sized spherical-tip indenter.