Description of Unloading Behavior of Berkovich Nanoindentation
We established a new expression to describe the nanoindentation unloading data by assuming that the Berkovich indenter behaves as a conical punch, rather than a paraboloid punch, and properly considering the effect of residual contact stress on the unloading load-displacement relation. The validity of this new approach was confirmed by analyzing the experimental data obtained for a series of brittle materials. It was shown that, compared with the generally adopted power law, this new expression has much clearer physical significance.
Wei Pan, Jianghong Gong, Chang-Chun Ge and Jing-Feng Li
H. Z. Miao et al., "Description of Unloading Behavior of Berkovich Nanoindentation", Key Engineering Materials, Vols. 280-283, pp. 1757-1760, 2005