Experimental techniques for investigating lubricated, compliant contacts

The study of Tribology between soft or compliant surfaces is not well understood despite its importance to many biological and engineering applications, ranging from synovial joints to rubber o-ring seals. It has also been shown that the science of Tribology and lubrication in compliant contacts is an important factor in the sensory perception and functionality of skin, hair and the oral cavity, and so has an immediate application of the design of consumer products such as skin creams, hair conditioners and foodstuffs. This thesis aims to improve our understanding of thin film lubrication between soft, deformable surfaces under light loading and low-pressure conditions. The primary focus of the thesis is the development of techniques by which to measure the film thickness between compliant surfaces, from the nano- to the micro-scale. Several experimental techniques currently exist for measuring film thickness in hard, metallic contacts and these are widely employed in Tribology research of engineering systems. However they require considerable modification to be applicable to compliant contacts. This thesis describes the development of two such techniques; · a optical interferometric technique; for measuring nano-scale thicknesses in compliant contacts; · a laser induced fluorescence technique; developed to enable measurement of lubricant thickness of relatively thick films in compliant contacts