Analyses of direct verification data of Rockwell diamond indenters by iterative regression method

Abstract

For the verification of Rockwell diamond indenters exactly compliant to the international definition, an iterative method with the least square circle fitting was introduced. This method was applied to the analysis of verification data obtained with a laser probe 3D profile measurement instrument. The geometry of a Rockwell diamond indenter was verified with the equipment as an example. Conventional analyses on cross sections of an indenter is demonstrated as well as three dimensional analysis of indenter geometry. The analyses on cross sections showed that the technique can be used to express the geometrical parameters described in the definition of CIPM/CCM/WGH properly, whereas three dimensional analysis enables to express the imperfection of geometry with fewer parameters. In addition, this technique can be applicable to determine equivalent geometrical parameters obtained with the optical measurement system currently used at the National Metrology Institute of Japan (NMIJ) to establish the national standard indenters. It is shown that the proposed method describes the geometry of indenter better than currently used method. These results suggest that the uncertainty of the national standard indenter could be improved through this high resolution geometry measurement and the multiple regression analysis NMIJ is using.