Research On The Life Evaluation Method Of Two-parameter Performance Degradation Of An O-ring

There are more and more long-life and high-reliability products in the aerospace,electronics,weaponry and other fields.Traditional life assessment methods based on accelerated life testing are difficult to predict the life of such products in a short time.Therefore,accelerated degradation testing is more and more widely used in life assessment.In this paper,an O-ring as a prone-to-fail seal is the research object.Based on the accelerated degradation testing,a binary degradation model is established to evaluate the life,and the model result is compared with that obtained from the natural storage testing.The results show that the model has a good evaluation effect.The main contents of this paper are:The methods of establish a degradation model with dual performance parameters are analyzed.The modeling methods of the degradation trajectory model and the Wiener process model are described.For the case of dual performance parameters,the method of expressing the reliability function when the parameters are independent or related is introduced.When the parameters are related,the method using Copula function to describe the parameter correlation is introduced in detail.Design of accelerated degradation testing scheme for an O-ring is discussed.The implementation conditions of the accelerated degradation testing are listed,and a test feasibility analysis is performed on an O-ring to determine whether it meets the implementation conditions.The method of determining test parameters such as stress level,performance parameters and failure criterion and so on is given,and finally the specific scheme of accelerated degradation testing is designed.Based on the results of the accelerated degradation testing,a degradation trajectory model is established to analyze the degradation law of the seal ring.According to the degradation data collected by the accelerated degradation testing,the degradation trajectory of each sample is obtained,and a degradation trajectory model is established based on this.Then the distribution type of the pseudo-failure life can be determined.Combined with the acceleration model,the storage life under normal stress is extrapolated,and the influence of a single parameter and independent parameters on the life evaluation result is analyzed.The methods of establish a degradation model based on binary Wiener process are analyzed.For the nonlinear degradation data,a time-scale conversion function is introduced to establish a binary nonlinear Wiener process model.In order to characterize the effect of individual differences on performance changes,the drift parameter is randomized.Segmental maximum likelihood estimation is used to estimate model parameters.The model is applied to the O-ring,and the difference between the life evaluation results is analyzed in the three cases of single parameter,independent parameters and related parameters.The life of the O-ring under natural storage conditions is evaluated and the effects of degradation models are analyzed.The life of the O-ring is predicted based on the natural storage testing,and the result is used to evaluate the effects of the accelerated degradation models.The equivalent temperature in the natural storage environment is obtained by the equivalent temperature model.The equivalent temperature is substituted into the accelerated degradation models to get the corresponding evaluation results.The life prediction result obtained from the natural storage testing is used as the quasi-true value to compare with the model evaluation results.