TEST-LOCATION SPECIFICATION BY MEANS OF HARDNESS MAPPING ON VICKERS BLOCK SURFACE |
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| Rugkanawan Kongkavitool, Satoshi Takagi, Takashi Usuda |
- Abstract:
- The non-uniformity of the hardness reference block is one of the important factors, which influence the hardness measurement. For calibration of hardness reference block, the elementary idea to reduce the error from this factor is to make the indentations at the distributed location as though covering the entire test surface with limited number of indentations. The principle to decide the appropriate numbers and locations of the measurement is to consider the trend and frequency of hardness distribution. “Stratified sampling” was introduced to the study on the assumption that the confidence of average hardness estimation would be increase with an appropriate test location. Six Vickers hardness reference blocks of 200, 600, 900 HV from 2 different manufacturers were selected for the experiment. The numbers of indentations were made on the entire surface of all blocks with three different levels of the test force. The analysis of hardness distributions was carried out with their measurement data with several aspects of the study. The possible trends of hardness distribution of the blocks, which, considered in the study i.e., circumferential divisions and radial divisions were selected to view the difference in hardness variation. The effect of stratified conditions to the measurement result was judged by using the analysis of variance (ANOVA). In most case of the experimental results, both stratifying conditions had significant influences on the reference blocks from both manufacturers with the different trends. Therefore, for higher confidence of hardness number estimation, the idea of test location specification should be taken into account by a considering of both stratifying conditions. Basically, the minimum numbers of indentations that give the reproducible hardness value upon the repeated measurement is desirable. By varying the stratifying conditions, the observed variations in hardness tended to decrease with the increasing number of strata. From the experiment, more than 6 to 12 strata were recommended for reliable hardness reference block measurement whereas 5 indentations were required as the minimum number in ISO 6507 part 3 [1].
- Keywords:
- Non-uniformity, Stratified sampling, ANOVA
- Download:
- IMEKO-TC5-2007-009.pdf
- DOI:
- -
- Event details
- IMEKO TC:
- TC5
- Event name:
- Symposium on Recent Advancements in the Theory and Practice of Hardness Measurement
- Title:
- 10th HARDMEKO Conference: HARDMEKO 2007
- Place:
- Tsukuba, JAPAN
- Time:
- 19 November 2007 - 21 November 2007