An experimental study of the contact of a rounded rigid indenter with a soft material block

Digital image correlation has been utilized for measuring the strains induced by the contact of a wedge-shaped indenter with a soft material block, which undergoes large deformation. The quality and extent of the experimental results allowed, for the first time, a detailed comparison with theoretical predictions using image decomposition and accounting for measurement uncertainties. Both in-plane strain and out-of-plane displacement calibrations of the digital image correlation system were conducted to establish the minimum measurement uncertainties (31.7 µε for in-plane strain and 0.65 µm for out-of-plane displacements) and to establish confidence in the measurements. It was concluded that the assumptions used in the theory were contravened when the depth of indentation exceeded 90% of the radius of the indenter tip so that the theory was no longer applicable.