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Improved elastomeric seal design based on nonhomogeneous material properties

The goal of this research was improving elastomeric seal performance based on seal material design. The specific seal failure mode considered was permanent deformation or compression set of O-rings, and sealing performance degradation due to this process is common to all types of elastomeric seals. The basis for seal design was identified as reducing the elastic strain energy in the seal since it drives the growth of permanent material deformation. The design concept developed was using variation of material behavior over the seal section to manipulate the level and distribution of elastic strain energy. Design studies used finite element analyses with experimentally measured material behavior to quantify effects of varying seal material characteristic on seal performance. Sealing performance was described in terms of compression set and seal-counterface contact pressure. Experimental O-rings were produced based on designs that included regions of less stiff material in the larger surrounding seal section. Performance of new design seals was compared to conventional one-material seals and improved sealing performance was demonstrated. With the modified design seals, both compression set and the rate of sealing contact pressure loss over time were decreased. There was a loss of initial maximum contact pressure with the inclusion of less stiff material regions, but it was shown that this effect can be mitigated by properly locating the softer material in the overall seal section. In summary, properly implemented material variations over the seal will result in lower strain energy content, lower rate of permanent deformation development and decreasing rate of loss of seal-counterface contact pressure.