CHARACTERIZATION OF ROCKWELL BALL INDENTER HOLDER SHAPE AND PROPERTIES, AND ITS EFFECT ON HARDNESS

Nae- Hyung Tak, Seong-Gu Hong, Gun Woong Bahng, Sang-Bo Bae

Abstract

Although ball indenter plays a key role in the measurement of Rockwell hardness, its verification procedure, which is essentially required to provide reliable data, has not been adequately detailed in ISO 6508; only the requirements for ball size are described. When considering the ball indenter is composed of two main parts, the ball and the ball holder, these insufficient requirements for the ball indenter can give rise to unorganized measured data and consequently result in an increase of uncertainty. In fact, many problems regarding the reliability of measured data are widely being reported in industries, as various types of ball holders are now being used due to the absence of their standard requirements. In this study, therefore, the influence of the ball holder on the hardness measurement was investigated. Four preferred types of commercial ball holders in the industry were selected and their shape and hardness were characterized. The role and importance of the ball holder in terms of hardness measurement were discussed in relation to the alignment of the ball indenter and plastic deformation of the ball holder. It was found that plastic deformation of the ball holder was caused by the difference in hardness between the ball and ball holder during indentation and this results in a large scattering of data.

Keywords

Rockwell hardness, ball indenter

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IMEKO-WC-2012-TC5-P6.pdf

DOI

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IMEKO TC

TC5 - Hardness Measurement

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