Investigation of wear of materials by laser speckle photography

This study utilizes a non-contact technique, laser speckle photography, to measure deformations associated with sliding wear. These deformations are those which occur on the side of a rectangular-section pin which is in sliding contact against a counterface disc. The side of the pin is illuminated by a pulsed ruby laser beam, and a double exposure specklegram is made to obtain deformations which occur between laser pulses. So, by appropriately sequencing pulses, deformation histories can be obtained, in situ. Since the exposed side of the thin pin specimen represents the cover layer under which subsurface sections lie, the deformation history observable through the laser speckle method reflects the deformation behavior which is occurring on subsurface planes. The strain fields associated with the deformations are also calculated by the usual methods which include nonlinear terms (Lagrangian formulation). Moreover, this research discusses the materials, apparatus and experimental techniques employed, and presents results obtained with several metallic specimens. Of particular interest is the extent of the plastically deformed subsurface zone for different materials. These fundamental data, obtained by the laser technique, yield direct displacement or strain histories for wear specimens. Such data are important for understanding wear phenomena, and for the development of engineering models for wear