Stylus Penetration Correction for the Calibration of Gauge Blocks of Dissimilar Materials by Mechanical Comparison

摘要

Non-steel materials of gauge blocks are increasingly gaining on their popularity, among them especially oxygen ceramics with its mechanical properties being close to the steel. Calibration of non-steel gauge blocs is therefore increasingly demanded. Most calibrating laboratories only have steel reference gauge block set and therefore cannot mechanically calibrate non-steel gauge blocs with the measurement uncertainty similar to the one for steel. For mechanical calibration of gauge blocks by comparison of dissimilar materials a significant increase in measurement uncertainty is typical. This is mainly the consequence of the differences in thermal expansion coefficients and uncertainty associated with the stylus penetration correction. With precise temperature control effects of differences in thermal expansion coefficients can be minimised, while elastical deformation as a consequence of stylus force for mechanical comparison is unavoidable. In order to minimise measurement uncertainty increase as a result of differences in mechanical properties, extensive research of stylus penetration at different GB materials has been performed and is presented in the paper. Hertzian formulas are used for calculation of the stylus penetration, for experimental research standard laboratory equipment is complemented with special designed probes in innovative way. Significant differences between analytical and experimental results have been detected. For the stylus penetration compensation experimental results have been used. Rightness of the decision has been proven in international intercomparison.