THE UNCERTAINTY EVALUATION OF NPL'S HARDNESS FACILITY

摘要

To understand the uncertainties in the calibration of hardness test blocks by NPL, it was necessary to evaluate the main factors contributing to the uncertainty in measurements made with the NPL hardness calibration machines. These factors were identified and then, where possible, directly verified. Factors that could not be directly verified were assessed using the best available information. The verifications covered the force required to produce hardness indents, the measurement of the size of these indents, and the characterisation of the indenters. As a result of the initial verification, modifications were made to the depth sensor on the Rockwell hardness tester.