Probability Prediction of Multiple Site Damage Cracks of Butt Jointing Structure

Multi-site damage (MSD) is a prevalent form of damage that occurs during the service life of aging aircraft, significantly compromising the structural integrity of the aircraft and posing a serious threat to its overall safety. In this paper, we examine the occurrence probability of MSD cracks in aircraft joint structures, aiming to provide technical support for the establishment of WFD evaluation methods. By leveraging the principles of fatigue statistics and incorporating S-N curves, we calculate the probability distribution of fatigue life of cracks at each detail in multi-detail joint plates with holes. Furthermore, we employ the Monte Carlo simulation method to predict the sequence of appearance of MSD cracks at the edges of holes within the joint structure, effectively estimating the probability of crack initiation. Our research findings reveal that the holes at both ends of the joint structure with MSD cracks are more susceptible to cracking, while the likelihood of cracking gradually decreases from the edge towards the center. To validate these predictions, we conducted tensile-tensile fatigue tests on multi-detail joint plates with holes. The test results show a strong correlation with the predicted outcomes, confirming the accuracy and reliability of our analytical approach.