The Fatigue Reliability Analysis Of Structures Based On The Duration Of Stochastic Process Exceeding Threshold

Traditional structural fatigue reliability analysis is mostly based on idealized models,and the factors affecting fatigue cumulative damage are not considered comprehensively.Most of them only consider the influence of stress cycle number,so there is still a big gap between the existing theory and the actual situation.The cumulative structural fatigue damage is related to the duration of the structural stress process beyond the safety threshold.Because it involves the analysis of the random process exceeding the safety threshold for many times,the theoretical analysis of this problem is quite difficult,so the influence of crossing the threshold holding time on the random fatigue cumulative damage has not been considered.Based on the recent progress of multiple crossover problems of stochastic processes,the following work is done in this paper:1,based on the existing time interval between two adjacent intersection Wiener process(beyond the duration of the threshold)analytic solution of probability distribution,Wiener process and non-zero threshold are discussed in a certain period of time the probability distribution,the number of cross cases and compared the different threshold based on the monte carlo method,the proposed numerical method to calculate the crossover probability,It provides a basis for the fatigue reliability analysis of Wiener random stress process.2.By considering the duration of the random stress process exceeding the damage threshold,the influence of the crossing threshold holding time on the cumulative fatigue damage of the structure is analyzed,the cumulative fatigue damage index considering the total duration of the crossing threshold holding time is derived,and the fatigue reliability analysis method considering the crossing threshold holding time is established.3.The proposed fatigue reliability analysis method is used to analyze the fatigue reliability of the key parts of a subway bogie and the suspenders of Yingzhou Bridge in different service periods,which verifies the scientific and rationality of the proposed method.Compared with the traditional method,the structural fatigue reliability analysis method based on the cross-threshold duration starts from the random stress process itself,and the influence of the stress process beyond the damage threshold duration on the fatigue cumulative damage is considered.