Philosophical magazine. A/Philosophical magazine. A. Physics of condensed matter. Structure, defects and mechanical properties · 2002 · 38 citations · 8 references
EngineeringMultiscale MechanicsMechanical EngineeringHardnessWork HardeningSharp IndentationMechanics ModelingElasticity (Physics)MechanicsStressstrain AnalysisStrain HardeningDeformation ModelingMaterials ScienceMechanical BehaviorSolid MechanicsMaterial MechanicsPlasticityMechanical DeformationMechanical PropertiesContact Deformation RegimesMechanics Of Materials
Abstract This investigation is predicated upon work by Mata et al. on the contact deformation regimes for strain-hardening materials. The results allow us to derive a general hardness equation for sharp indentation of elastic-power-law plastic materials. The formula H/σr = 1.440 + 0.264 ln(E/σr) is found to provide estimates of hardness H for a wide range of elastoplastic responses as long as the contact deformation regime lies within the elastic-plastic transition. This formulation is a modification to previous formulae derived for solids that do not exhibit strain hardening; where E is Young's modulus and the yield strength σys has been replaced by σr, the stress level in the uniaxial stress-strain curve at a characteristic strain ϵr of 0.1. The development of radial flow patterns is regarded as a necessary condition to the validity of the above equation. As the deformation underneath the indenter evolves to an uncontained mode, the radial flow patterns that are characteristic of the elastic-plastic transition are increasingly disrupted to a point where non-radial flow leads to piling-up of material at the contact boundary.
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