Research On The Reliability Of Civil Airplane Wing-Fuselage Connection Structure With Multiple Site Damage

The structural life index of the modern civil aircraft is increasing,and the load environment is more and more complex,it is very meaningful to combine the long-life and reliability design of aircraft structure and integrate the long-life reliability design into the practical engineering practice of civil aircraft design,making aircraft design easy to operate,verifiable,and having significant economic benefits.During the long term of flight task,to the structure of wing fuselage,the aircraft will cause multi-site damage due to fatigue load and other factors,which will reduce the residual strength of the structure rapidly and result in serious flight accidents.It is very important to do research on the reliability of multi-site damage.This paper mainly does research on the reliability of aircraft wing-fuselage connection structure with multi-site damage.The reliability of crack propagation depends on a number of random variables.It is focused on whether the life of the multi-site crack propagation can reach the critical life based on these random variables,calculating its reliability and providing safety protection for aircraft wing fuselage connection structure.Firstly,on the basis of single crack,the interaction between multi-site cracks is introduced,and the theory of single crack is extended to the propagation of multi-site cracks,calculating the stress intensity factors and interaction factors in various modes of multiple cracks.Secondly,selecting the wing-fuselage connection structure,based on the theory of expansion in the deterministic crack,add multiple random variables,such as fracture toughness,initial crack length,crack propagation rate and the stress of the extreme,which follow the random distribution function-the lognormal distribution,and then transfer the problem into the non-deterministic crack growth.The fatigue life of the structure is calculated by interfering with all the random variables.According to the failure criterion,a failure probability of the structure is obtained,and its reliability is further revealed.In addition,The appropriate crack propagation model is selected according to the corresponding conditions.Finally,based on the above theory,we use the Monte-Carlo method for large samples.According to each input data sample drawn,analyse the crack propagation life by a deterministic crack propagation theory,judge whether it is invalid or not,then obtain its reliability combining with the total number of samples.Depending on all above studies,the reliability of the structure with the multi-site damage can be evaluated toassure the safety of the aircraft structures.