Abstract
This paper describes an overview of the capability of the NMIs that participated on the CCM Pilot Study measurement systems, conducted by the CIPM/CCM/Working Group on Hardness, to characterize the Rockwell hardness diamond indenter geometry, by measuring the included cone angle, the straightness of the generatrix, the spherical tip radius, the deviation of the local radius and the tilt angle. Nine NMIs took part in this study: INMETRO (Brazil); INRiM (Italy); KRISS (South Korea); NIM/PR (China); NIMT (Thailand); NIST (USA); PTB (Germany); TUBITAK UME (Turkey); VNIIFTRI (Russia), where INMETRO (Brazil) served as pilot laboratory.
Highlights
International hardness measurement equivalence between the National Metrology Institutes (NMIs) is the role of the Consultative Committee for Mass and Related Quantities (CCM) Working Group on Hardness (WGH) within the International Committee of Weights and Measures (CIPM) [1]
The second one was based on the NIST Consensus Builder (NICOB), which is consistent with the combination of measurement results obtained independently by different laboratories or measurement methods [4, 5]
The other method used to analyze the results of the comparison, and to determine the dispersion of the obtained data points by the labs was the method based on the NIST Consensus Builder (NICOB)
Summary
International hardness measurement equivalence between the National Metrology Institutes (NMIs) is the role of the Consultative Committee for Mass and Related Quantities (CCM) Working Group on Hardness (WGH) within the International Committee of Weights and Measures (CIPM) [1]. There have been numerous discussions among the members of the CCM-WGH concerning the difficulty in obtaining calibration-grade Rockwell hardness diamond indenters having the correct shape within geometric tolerances as specified in international standards. The primary reason is that the crystallographic structure of diamond makes it extremely difficult to grind and polish to the required Rockwell indenter shape. The accurate measurement of a Rockwell indenter’s geometrical parameters is a difficult and often time-consuming process due to the conical and spherical indenter geometries and the optical transparency and high reflectivity of the polished diamond. The CCM-WGH agreed to carry out a Pilot Study (PS) on the measurement of Rockwell hardness diamond indenter geometries in which the laboratories of National Metrology Institutes (NMIs) should participate. The Pilot Study was conducted from December 2011 until January 2015, with all but the repeat measurements of the Pilot Laboratory completed by March 2013
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