The properties of random surfaces of significance in their contact.

In modern engineering there is an urgent need for a deeper understanding of the nature of surface texture and its influence upon the functioning of the element of which it forms a part. Of particular importance, in this connection, is the behaviour of surfaces in stationary and sliding contact. Investigations of the contact of surfaces, on the one hand, and the evolution of methods of surface specification and characterisation, on the other, have developed more or less independently. This thesis attempts to bridge the gap between these two areas of study. The main emphasis of the work has been upon random surfaces which are produced by a significant proportion of modern manufacturing methods. The theories used have been drawn from those employed in the study of other types of random processes. Both these theories, and the experimental evidence used to support them have been usually presented in digital form; therefore some emphasis has been placed upon the problems involved in the analysis of data presented in this form. The theoretical analysis is concerned with the representation of a surface profile as a random signal and the significance of this for the properties of surfaces of significance in their contact. This then allows the development of a theory of the movement of a second body over such a random profile. The friction and wear of random surfaces is tackled through the analysis of results obtained from well instrumented experiments; this suggests that a stochastic approach to the tribology of random surfaces is well justified. Finally an attempt has been made to provide a broad fundamental analysis of the generation of such surfaces. In this way it is hoped that the work provides a basis for the classification or the typology of surfaces in terms both of their functional behaviour and of the relationship of this to the details of their generation.