A newly developed theory on plasticity makes it possible to include elastic effects, which play a major role when using blunt hardness indenters. This article reviews the new theory and explains several phenomena associated with practical hardness testing. In the indentation hardness test, a blunt indenter that approximates a flat punch is forced into a plane surface. The effective cone angle for most indenters is such that some upward flow results even when there is sufficient material surrounding the indenter to provide a full elastic constraint. When loaded by a blunt indenter, materials with high values of Young's Modulus of Elasticity/uniaxial flow stress (E/Y) (metals) appear to develop a Hertzian stress distribution over the contact. In contrast, materials with low values of E/Y (glasses and polymers) develop a uniform distribution of stress.
Milton C. Shaw, Gabriel J. DeSalvo, The Role of Elasticity in Hardness Testing, Mechanical Testing and Evaluation, Vol 8, ASM Handbook, Edited By Howard Kuhn, Dana Medlin, ASM International, 2000, https://doi.org/10.31399/asm.hb.v08.a0009224
Download citation file: