Corrosion Fatigue Reliability Analysis Of Typical Mechanisms Of Carrier Aircraft

Carrier-based aircrafts are parked on the deck or in the hangar for most of their lifetime,residing and cruising with the carrier in the ocean.Thus,they are liable to the coastal climate's harsh influence of high temperature,high humidity and salt fog.Folding wing is one of the key components affecting carrier-based aircrafts' flight safety.Under cyclic loading,the major failure is fatigue damage.Coupled with corrosive effect brought by the severe service environment,the interaction of corrosion and fatigue will result in a significant decline in structure bearing capacity,accelerate crack formation and expansion,and thereby severely reduce structures' residual strength and life.Considering the impact of corrosive environment,and based on the current progress on fatigue reliability study,corrosion fatigue reliability analysis method is investigated for the key parts of a certain type of carrier-based aircraft's folding wing structure.Considering corrosion effect,DCR method of corrosion fatigue reliability is analyzed.In this method,corrosion effect is valued by the decrease of DFR value.And then corrosion fatigue life with certain reliability is calculated based on fatigue cumulative damage theory.With existing test data,corrosion fatigue life and reliability of aircraft structure can be obtained under multi-stage constant amplitude loading.A suitable analysis process for aircraft structure corrosion fatigue life and reliability is summarized in this paper.Also,calculation method of structure corrosion fatigue life and reliability under multi-stage load,under any reliability and confidence level,is put forward,as well as reliability variation with time.Taking the folding wing of a certain type of carrier-based aircraft as an example,a model for analyzing corrosion fatigue life and reliability is established.First,the structure constitution and mechanism is analyzed.Geometric model of folding wing is established using threedimensional modeling software,and then stress analysis is made using finite element analysis software.Therefore,corrosion fatigue critical components are determined to be front beam and middle beam joint single lugs.Combined with folding wing fatigue load spectrum,the two lugs' stress spectrums are obtained.Then,using DCR method,corrosion fatigue reliability analysis of the lugs is carried out.Corrosion fatigue life under any reliability and any confidence level is obtained,as well as reliability R-T curve.The results show that corrosion fatigue life of front beam joint single lug under 99.9% reliability and 90% confidence level is 25 years.Corrosion fatigue life of middle beamjoint single lug under 99.9% reliability and 90% confidence level is 23 years.And the comparison between corrosion fatigue life and fatigue life without corrosion is made,which shows that corrosive environment greatly reduces the anti-fatigue performance and fatigue life of the structure.This method can well predict the reliability and performance of the structure,and it is an effective method for engineering application.In addition,the influence of the parameters such as structure dimension parameters,environmental correction coefficient and annual flight frequency on fatigue life and reliability of middle beam joint single lug is also analyzed.The results show that the corrosion fatigue life of the lug can be improved by ameliorating design,increasing structure size and applying anticorrosion measures.