Comments on “Extracting the plastic properties of metal materials from microindentation tests: Experimental comparison of recently published methods” by B. Guelorget, et al. [J. Mater. Res. 22, 1512 (2007)]: The correct methods of analyzing experimental data and reverse analysis of indentation tests

Abstract

Based on microindentation experiments of three different metals, Guelorget et al. [J. Mater. Res. 22, 1512 (2007)] have compared the performance of five different indentation methods on extracting material plastic properties—among them, three papers were proposed by Cao and Lu [Acta Mater.52, 4023 (2004); J. Mater. Res.20, 1194 (2005); J. Mech. Phys. Solids53, 49 (2005)] and two papers were published by our group [Ogasawara et al., Scripta Mater.54, 65 (2006); Zhao et al. Acta Mater.54, 23 (2006)]. They argued that the performances of our techniques in [Ogasawara et al., Scripta Mater.54, 65 (2006); Zhao et al. Acta Mater.54, 23 (2006)] were quite poor. Here we show that Guelorget et al. [J. Mater. Res. 22, 1512 (2007)] have made quite a few mistakes and problematic steps when they handled the experiment data and performed reverse analysis. Indeed, the material plastic properties extracted from the correct procedures based on our papers [Ogasawara et al., Scripta Mater.54, 65 (2006); Zhao et al. Acta Mater.54, 23 (2006)] are much better and more stable than that reported in Guelorget et al. [J. Mater. Res. 22, 1512 (2007)]. Several general issues related to interpreting microindentation data and reverse analysis are also discussed, which may serve as important guidelines for similar studies in the future.

On radial crack and half-penny crack induced by Vickers indentation

“…The crack systems were found to be material dependent, in particular the ratio between elastic modulus and hardness, which brings the importance of varying material elastoplastic properties during the indentation cracking analysis. Although the indentation force-displacement curve was widely used in extracting elastoplastic properties (Ogasawara et al 2005(Ogasawara et al , 2008Chen et al 2006aChen et al , 2007, they were found to be continuous during the event of cracking and they were the same even when different crack systems were produced (Cook & Pharr 1990). Thus, it was suggested that the use of the indentation force-displacement curve is not a reliable method.…”

“…Although the indentation force-displacement curve was widely used in extracting elastoplastic properties (Ogasawara et al 2005(Ogasawara et al , 2008Chen et al 2006aChen et al , 2007, they were found to be continuous during the event of cracking and they were the same even when different crack systems were produced (Cook & Pharr 1990). Thus, it was suggested that the use of the indentation force-displacement curve is not a reliable method.…”