Letter | Published:

Reversed Plastic Flow during the Unloading of a Spherical Indenter

Naturevolume 199page1282 (1963) | Download Citation



THE process of indentation of a metal surface by a hard spherical indenter has been examined in considerable detail by Tabor1 and others. If the indenter makes contact with the surface over a circular area of radius a under the action of a load W, the mean contact pressure pm=Wa2. Tabor showed that plastic yielding begins beneath the surface of the metal when pm reaches the value 1.1 Y (where Y=yield stress of the metal in simple tension). As the load is increased and a marked plastic indentation develops, the mean pressure approaches a value which is independent of the load given by: where c has a value of approximately 3. This is the state of affairs in a Brinell hardness test.

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  1. 1

    Tabor, D., Hardness of Metals (Oxford Univ. Press, 1951); Proc. Roy. Soc., A, 192, 247 (1948).

  2. 2

    Tyler, J. C., Burton, R. A., and Ku, P. M., paper presented at the A.S.L.E. Annual Meeting, New York, April 1963.

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  1. Engineering Department, University of Cambridge

    • K. L. JOHNSON


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