Linear strain hardening in elastoplastic indentation contact

Finite-element analyses for elastoplastic cone indentations were conducted in which the effect of linear strain hardening on indentation behavior was intensively examined in relation to the influences of the frictional coefficient (μ) at the indenter/material contact interface and of the inclined face angle (β) of the cone indenter. A novel procedure of “graphical superposition” was proposed to determine the representative yield stress Y_R. It was confirmed that the concept of Y_R applied to elastic-perfectlyplastic solids is sufficient enough for describing the indentation behavior of strainhardening elastoplastic solids. The representative plastic strain of ε_R (plastic) ≈ 0.22 tan β, at which Y_R is prescribed, is applicable to the strain-hardening elastoplastic solids, affording a quantitative relationship of Y_R = Y + ε;_R (plastic) × E_P in terms of the strain-hardening modulus E_P. The true hardness H as a measure for plasticity is estimated from the Meyer hardness H_M and then successfully related to the yield stress Y as H = C(β,μ) × Y for elastic-perfectly-plastic solids and as H = C(β,μ) × Y_R for strain-hardening solids, by the use of a β- and μ-dependent constraint factor C(β,μ) ranging from 2.6 to 3.2.