On the basis of the discussions, some conclusions can be obtained as followings:

　　1) The finite element model of an O-ring is built, which provides designers a numerical simulation model of O-ring;

　　2) The seal reliability function of an O-ring is established, and the reliability of the O-ring quantified;

　　3) The distribution fitting of maximum contact stress of the O-ring is done, the result shows that the maximum contact stress follows normal distribution;

　　4) The analysis of the effect of variation of parameters on the seal reliability of O-ring is done, the result indicates the seal reliability increases with the increasing of mean of gas pressure, pressure ratio,and friction coefficient, then begins decrease when the mean grow to some extent.;

　　5) The method of analyzing the effect of the variation of design parameters on the reliability index of Oring,can greatly reduces test cost, provides an useful tool for valve designers.

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