INVESTIGATION OF INFLUENCE FACTORS ON HARDNESS CHANGE OF 25 AND 40 HRBW REFERENCE HARDNESS BLOCKS

Tassanai Sanponpute, Nitiwat Sasom, S. S. K. Titus

Abstract

National institute of metrology (Thailand), NIMT studied behavior of hardness change on 25 and 40 HRBW. There is not only number of indentations but also other several influences cause to stability of hardness measurement. Some dominance factor such as diameter size of anvil, block thickness and indenting pattern were taken into account for scope of experiments. Set of 25 and 40 HRBW reference hardness block were provided, consisting of 6, 8.5, 10.5 and 11 mm thickness. Hardness tested on one with various anvil sizes, 6, 12 and 60 mm diameter. The tests proceeded on different indenting patterns, spread and huddle patterns respectively. <BR />Investigations exposed that stability of hardness measurement is mainly affected from several factor that mention above. Each indentation pattern makes hardness change with uniquely increasing and steadying trends for spread and huddle patterns. Amounts of hardness change seem to be inversely proportion to hardness level. Besides, the number of indentations make bottom surface of block becomes more and more concave. However, the blank block is generally produced slightly convex surface. Thus, at first several test results showed unexpected trend meanwhile, bottom surface is still convex. In additional, anvil size is not more effect. As found that on the huddle patterns, the results of those three groups by using various anvils 6, 12 and 60 mm are not significantly different. On the other hand, results using 60 mm have smaller hardness change than one when testing with spread patterns.<BR />Thickness of block also effect on stability. However, for the group of spread pattern showed similar result between in the groups of various thickness blocks. Meanwhile, test result of 11 mm thickness block is more stability than other thickness for huddle pattern.

Keywords

reference block, hardness change and bending

Download

IMEKO-TC5-2014-005.pdf

DOI

-

IMEKO TC

TC5 - Hardness Measurement

Back to the proceedings