CALIBRATION OF DEPTH-SENSING INDENTATION INSTRUMENTS - AN INTERNATIONAL INTERCOMPARISON

A round-robin has been carried out to validate calibration and measure ment procedures for various designs of depth-sensing indentation instr ument. The procedures used in instrument calibration and for the round -robin exercise are detailed. Hardness and Young's modulus values were obtained for the test materials used in the round-robin experiments o ver the load range 20-1000 mN. Both hardness and Young's modulus value s showed a dependence on load with increasing values at lower loads. T he effect was more marked for hardness than for Young's modulus. Uncer tainties (95% confidence) in measurement varied greatly between the pa rticipants, the best being +/-5% and in the worst case this was as gre at as +/-100%. These differences were related both to the calibration accuracy achieved by the different participants and to the repeatabili ty of measurements for the various instruments. Where accurate calibra tion was possible and instrumentation was adequate, agreement with acc epted hardness and Young's modulus values was often better than +/-10% ; thus the calibration procedures and measurement methods are acceptab le and can be considered as suitable for adoption as standards.