Modelling and analysis of functionally graded surface contact: a review

Abstract In recent decades, functionally graded materials (FGMs) have witnessed substantial growth in their application and received significantly increasing research attention. Beyond their use as bulk components, FGMs have been observed to improve the surface behaviour at different levels when implemented at or in the vicinity of contacting surfaces. Proper and efficient implementation of material gradation contributes towards strengthening of interacting surfaces for a varied range of engineering applications. In order to fully harness these benefits, a detailed understanding of the interactions taking place at the contact interface and its neighbourhood is essential. While existing reviews primarily focus on the behaviour of bulk FGM components (e.g., beams, plates etc) or general contact mechanics, a comprehensive literature review, specifically dedicated to the contact analysis of functionally graded surfaces, remains absent from the literature. Addressing this gap, the current paper aims to carry out a systematic review and classification of the extensive body of theoretical research on functionally graded surface contact to provide a comprehensive review of the field. The review encompasses wide range of contact analyses involving different type of contact conditions (normal, tangential and rolling contact), gradation models and contact complexities. It highlights the evolution from analytical geomechanics models to modern computational frameworks, revealing how tailored gradients can effectively enhance damage resistance and improve load-bearing capacity. Lastly, based on the reviewed literature, an effort is made to show the future directions in this evolving domain.