The effect of orthotropic material gradation on the plane sliding frictional contact mechanics problem

With the advent of new functional and intelligent non-conventional materials, understanding the behavior of these materials in different contact conditions over the conventional materials is one of the most crucial aspects in early design process for coated systems. Therefore, the sliding contact problem for a functionally graded orthotropic coating–substrate system and a rigid cylindrical punch is considered in this article to study the aforementioned aspects. The functionally graded orthotropic coating is modeled to be bonded to an isotropic substrate of finite thickness and is loaded by a sliding rigid cylindrical punch under plane strain conditions. For the material orthotropy, five different real orthotropic materials are utilized and the stiffness coefficients of each principal direction are graded separately. Navier’s equations are converted to ordinary differential equations using the Fourier integral transformation technique. Then, the algebraic equations are solved and the problem is cast into a singular integral equation. A parametric finite element analysis based on augmented contact method is also conducted. The normalized surface stress distributions and the normalized contact boundaries obtained from finite element analysis are validated with the results obtained from singular integral equation approach. The results of this study may be helpful for engineers in design and optimization of the characteristics of non-conventional coatings that are used as thermal or structural barriers and wear-resistant surfaces in engineering applications.