Study on Similarity Low of Hardness Using Small Ball Rebound Test, eNM

Takashi Yamamoto, Masayuki Yamamoto, Mizuki Watanabe, Kensuke Miyahara

Abstract

We investigated the law of similarity for hardness with respect to a newly-developed small ball rebound hardness test method. In the case of a spherical indenter hardness test such as that used for Brinell hardness, only if <i>d</i>/<i>D</i> were a constant, where <i>D</i> is the diameter of the indentation and is the diameter of the spherical indenter, would the indentations and the deformation regions caused by spherical indenters of different sizes have similar shapes, and therefore allow the same hardness values to be obtained. Using hardness blocks of 200 to 900 HV made of eutectoid carbon steel as specimens, as the measure of hardness we investigated the coefficients of restitution for 5, 3, and 2 mm alumina ceramic ball indenters with an impact velocity of 10 m/s. The test results were that the coefficients of restitution agreed well with the values of <i>d</i>/<i>D</i> for spherical indenters of different sizes, so we believe that this test method is a rebound hardness test method that satisfies the law of similarity for hardness, as is true for Vickers hardness.

Keywords

law of similarity for hardness, rebound hardness, hardness reference block, coefficient of restitution

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IMEKO-TC5-2017-007.pdf

DOI

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IMEKO TC

TC5 - Hardness Measurement

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