Identification Method Study Of Failure Mechanism Consistency For Rubber Sealing Materials In Accelerated Degradation Testing

At present,accuracy of lifetime prediction is not high for rubber sealing materials based on accelerated degradation testing.The basic reason is that the failure mechanism in accelerated degradation testing is likely different from that in normal storage condition.Therefore,it is meaningful to study identification method of failure mechanism consistency for rubber sealing materials in accelerated degradation testing.In this paper,focusing on the sealing material in missile non-electric components,identification of failure mechanism consistency for rubber sealing materials in accelerated degradation testing is systematically studied by combining with the theory of rubber failure mechanism,data analysis,and test validation.The main contents are as follows:1.By studying the Arrhenius model which is the accelerated model of rubber material accelerated degradation testing,there is an exponential relation between the degradation velocity of rubber and negative reciprocal of stress value when the failure mechanism keeps identical in the accelerated aging testing process.The activation energy under every temperature stress level is obtained through the relationship between the degradation velocity of permanent compression set value and temperature stress and least square method.According to activation energy theory,an identification method of failure mechanism consistency for rubber materials is proposed in accelerated aging testing.Taking the accelerated aging testing data about the nitrile rubber-26 sealing gasket as an example,the method is preliminarily tested.2.On the basis of gray theory,it is proposed that an identification method of failure mechanism based on equal dimension and new information gray forecast model and the selection method of the optimal dimension.The change point of the failure mechanism is found by comparing the difference between actual value and the predicted value.Besides,simulation data is generated according to the principle that the activation energy keeps same if the failure mechanism consistency.By analyzing data,the method is proved that the change point of the failure mechanism can be found.3.Statistical analysis problem about the step stress accelerated degradation testing is described.In combination with the Nelson cumulative failure model and the relationship between the degradation velocity,degradation time and Arrhenius model,analytical method about data conversion of the step stress accelerated testing is given.By analyzing model parameter and minimizing the target value,the criterion function about the change point of failure mechanism in the step stress accelerated degradation testing has been proposed.Feasible validation methods for the model proposed with simulation data has also been given.4.Taking cylindrical silicone rubber samples as test object,identification method of failure mechanism consistency based on gray theory has been tested by designing and carrying out the constant-stress accelerated degradation testing.Results indicate that the method can effectively test whether the failure mechanism changes in accelerated degradation testing or not.