Determination of tensile properties by instrumented indentation technique: Representative stress and strain approach

Tensile properties can be evaluated by defining representative stress and strain with the parameters obtained from instrumented indentation tests using a spherical indenter. The accuracy of this approach depends strongly on how the contact depth is analyzed and how the representative stress and strain are defined. The primary factors influencing the determination of contact depth, pile-up/sink-in and elastic deflection, were quantified by analyzing indentation morphology by finite element simulation; then plastic pile-up/sink-in behavior was formulated in terms of the strain-hardening exponent and the ratio of indentation depth to indenter radius. For the representative strain, the definition by tangent function was determined to be more appropriate for assessing tensile properties based on derived behaviors of the strain-hardening exponent. This approach was experimentally verified by comparing tensile properties of 10 metallic materials from uniaxial tensile tests and instrumented indentation tests.