Effects of Contact Conditions on Sealing of a Thin Rubber Coating

Leakage occurs between contact surfaces due to the surface roughness. In general, soft materials such as rubber are used to perform a sealing function. Softmetal used as an engine seal material, is a stainless steel plate coated with rubber. In order to seal a fluid, it is necessary to design the rubber coating and the contact pressure with consideration of the surface roughness. In this study, leak tests are conducted with the softmetal, and the effects of contact conditions, such as surface roughness, load, rubber thickness and rubber material are investigated. A differential pressure system using nitrogen gas was constructed for the leak test, and a surface of anisotropic roughness is adopted. The size of the clearance due to the geometrical shape of surface asperities is calculated from an indentation test. A model of rubber compliance to surface asperities is proposed, which predicts the sealing contact pressure with the rubber thickness. The result predicted from the model is compared with the result of the leak test, and it is possible to predict the sealing contact pressure and the rubber thickness.