Report of Pilot study on Brinell hardness comparison CCM.H-P3

This is the pilot study report of Brinell hardness comparison organized by Consultative Committee for Mass and Related Quantities, Working Group on Harness (CCM-WGH). The measurand is the Brinell hardness of the blocks. The artifacts circulated are 250 HBW, 350 HBW and 450 HBW. The measurement hardness scales are 1/30, 2.5/187.5, 5/750, and 10/3000. For the 10/3000 scale, 350 HBW and 450 HBW are compared. The additional items are circulated to investigate the bias of the Brinell hardness measurements. One is the 2D indentation, namely “artificial indentation”, which is thin metal layer with a hole deposited on the glass plate. The second one is the 3D indentation, “Reference indentation”, which is the designated Brinell indent on each circulated artifact. The 2D indentation can be used to know the edge-determination condition including calibration of diameter measuring apparatus, and 3D indentation can be used to know the difference among institutes regarding the Brinell indentation diameter. This report of Brinell hardness comparison was firstly planned as a Key comparison for Brinell hardness (CCM.H-K2). A large bias were found in the first draft report which is due to the Numerical aperture of the observation optical system used to the indentation diameter measurement.