Dual flat-spherical indentation for extracting elastic–plastic properties from rough metallic surfaces

[Display omitted] •A dual flat-spherical indentation (DFSI) technique is developed for rough metallic surfaces.•Effects of surface roughness on spherical indentation (SI) techniques are numerically demonstrated.•Flattening of rough surface by flat indenter varies with surface roughness Ra and material properties.•For Ra = 0~20 μm, load-depth curves from flattened rough surfaces are comparable to those from SI.•DFSI technique is demonstrated for evaluating material properties from rough metallic surfaces. In this work, a dual flat-spherical indentation (DFSI) technique is developed for evaluating elastic–plastic properties from rough metallic surfaces. Since indentations on rough metallic surface produce dissimilar load–displacement (P-h) curves for the same material, finite element (FE) analyses and experiments demonstrate that DFSI method, in which rough surface is flattened by flat indenter before spherical indentation, extracts reproducible P-h curves from the flattened rough surface. Optimized indentation parameters are obtained by investigating the effects of surface roughness, flat indenter diameter, indentation depth on P-h curves. This allows to employ conventional spherical indentation (SI) method for property evaluation from DFSI P-h curves. The results are in good agreement with those from ideal smooth surface, and for rough surfaces (Ra = 0~20μm) common in engineering practice, the applicability of DFSI method is verified.