A novel nanoscaled adhesive contact model for functionally graded coating

Functionally graded material (FGM) layer-substrate systems offer advantages over conventional homogeneous layer-substrate systems in various engineering applications. This study introduces a new nanoscale adhesive contact model for an exponentially graded FGM layer-substrate system, incorporating adhesion contributions from all molecules instead of only contact surface, through the Lennard-Jones (LJ) potential and the Hamaker summation method. A parametric analysis investigates the effects of layer thickness, ratios of the work of adhesion, and elastic modulus ratios on adhesive contact. The results show that the layer thickness affects adhesive interaction forces significantly within a confined range. Adhesive forces in FGM layers fall between those in homogeneous layers with equivalent surface and bottom moduli. Adhesive forces increase with higher adhesion work ratios and elastic modulus ratios. FGM layers exhibit higher adhesive forces in soft layers and lower forces in stiff layers compared to homogeneous cases. Although the modification on adhesive forces is less pronounced than in homogeneous layers, the FGM layer improves subsurface von Mises stress continuity and reduces stress concentration in stiff layers. Moreover, the possibility of plastic deformation is identified. This study enhances the understanding of adhesive contact in FGM systems and provides insights for optimizing device design in engineering applications.