Depth-sensing indentation at macroscopic dimensions

A macroscopic-scale depth-sensing indentation apparatus with the ability to be mounted on an inverted microscope for in situ observation of contact events was calibrated using the Oliver and Pharr [J. Mater. Res. 7, 1564 (1992)] procedure with a two-parameter area function. The calibrated Vickers tip was used to determine the projected contact area at peak load and the modulus and hardness of a variety of non-metallic materials through deconvolution of the measured load-displacement traces. The predicted contact area was found to be identical to the measured area of residual contact impressions. Furthermore, for transparent ceramic materials the projected contact area during loading was found to be the same as the area measured from the diagonal of post-indentation residual contact impressions. The modulus and hardness values deconvoluted from the load–displacement traces were compared with independent measurements. The effects of sample clamping, column compliance, and tip radius on the load–displacement data and inferred materials properties were also examined. It is suggested that the simplicity of instrumentation and operation, combined with the ability to observe indentations optically, even in situ, makes macroscopic-scale depth-sensing indentation ideal for fundamental studies of contact mechanics.