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

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.