Determination of the Load-Independent Hardness by Analyzing the Peak-Load-Dependence of the Unloading Slope in Nanoindentation
By assuming that the test material has a load-independent nanohardness number, a linear relationship was predicted to exist between the reciprocal of the initial unloading stiffness, 1/SM, and the inverse square root of the peak load, (1/Pmax)0.5, and the load-independent hardness can be obtained directly from the slope of the 1/SM−(1/Pmax)0.5 straight line. This prediction was then verified by analyzing the experimental data obtained on soda-lime glass and a tetragonal ZrO2 polycrystalline. The indenter area function established based on the resultant load-independent hardness was found to deviate from the perfect Berkovich indenter and such a deviation can be attributed to the indenter deformation occurring during indentation as well as the indenter tip rounding.
Wei Pan, Jianghong Gong, Chang-Chun Ge and Jing-Feng Li
J. H. Gong "Determination of the Load-Independent Hardness by Analyzing the Peak-Load-Dependence of the Unloading Slope in Nanoindentation", Key Engineering Materials, Vols. 280-283, pp. 1761-1764, 2005