THE INFLUENCE OF THE BALL ON THE BRINELL HARDNESS TEST QUALITY
Abstract
The Brinell hardness tester with carbide and steel balls was calibrated and thereafter the hardness of ten samples of steel STN 41 1600 were measured by four appraisers. The uncertainty of calibration and of hardness measurement were calculated. The results obtained with carbide and steel balls were confronted using uncertainty analysis, measurement systems analysis (MSA), analysis of variance (ANOVA), unpaired t-test and Z-score. The hardness tester is not considered satisfactory because the values of Urel and Er of calibration exceed the values permitted by the standard for both balls. The statistically significant difference between the results of hardness obtained by carbide and steel balls depends on appraisers according to t-test. Measurement system analysis confirmed some influence of used ball materials for the results of individual appraisers on the capability of hardness measurement process in accordance with the results of z-score and ANOVA. The difference between average values of Urel of steel and carbide balls is more significant as at aforesaid methods.
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