Plasticity evolution in a coated sphere compressed by a rigid flat

• Plasticity evolution in a coated spherical contact is investigated.
• The critical interferences at yield inceptions are presented.
• A new criterion for substrate plasticity level is suggested.
• The boundaries of the evolving plastic zones are discussed.
• The effect of plasticity level on the mean contact pressure is demonstrated.

A finite element analysis is used to study the plasticity evolution in a coated sphere compressed by a rigid flat. This is done for hard coatings with moderate to large thicknesses and a wide range of material properties. Empirical expressions are provided for critical interferences of the first and second yield inceptions, in the coating and on the substrate side of the interface, respectively. A new criterion for substrate plasticity level (SPL) is suggested, which seems to control the plasticity evolution within the coating. Plasticity boundaries are presented, showing that a third yield inception may occur as the interference increases. Also, some complex behavior of elastic core formation below the contact area that causes reduction in the mean contact pressure is shown as the SPL increases.