Characterization of deformation field in plane-strain indentation of metals

A study has been made of the deformation field in plane- strain indentation of metals with a flat punch. Deformation field parameters such as velocity and strain rate have been measured using the technique of particle image velocimetry. For this purpose, images of the indentation region were recorded in situ during the deformation process, and motion of 'asperities' specially introduced onto a side of the sample being indented was analysed. The velocity and strain rate fields in and around the indentation zone were obtained from an analysis of the asperity motions. The measurements have shown, among other things, the presence of a dead metal zone underneath the indenter, the formation and evolution of regions of intense strain rates or shear bands and a linear variation of the strain rate with indentation speed. Many of the characteristics of the deformation field, e. g. slip lines and dead metal zone, compare favourably with those inferred from classical solutions for this indentation problem. Extensions of the technique for the study of strain field around indentations and deformation in plane- strain indentation by wedges and cylinders are discussed.