New analytical procedure to determine stress-strain curve from spherical indentation data

Spherical-indentation process was analyzed by finite element (FE) method. A systematic analysis of relationship between indentation parameters and true stress/plastic-strain (o,-ep) curve was performed for a range of material properties. An existing method relates the ratio or residual contact diameter, d, and indenter diameter, D, to ep by the well-known Taborʹs empirical equation E e = 0.2d/D. The method is based on parameters of residual indentation, where a loading-unloading cycle needs to be made in order to calculate a point on o,-ep curve. A new analytical approach is presented which relates the indentation data continuously measured during loading to at-ep curve. ep calculated by the new method is in the range from yield strain to a strain between 0.3 and 1.6, depending on materialʹs strain hardening properties. In addition, different measures of indentation diameter are discussed and their influence on the resulting a,-ep curve analyzed. Experimental work was performed by an instrumented spherical-indentation technique in order to verify the FE analysis results. A good agreement between the FE and experimental results was obtained. © 1998 Elsevier Science Ltd. All rights reserved