Strength And Fatigue Life Analysis Of Multilayer Bellows For Aircraft

Due to the good resistance to interior pressure, corrosion, high temperature, impact, and the high strength, multiply bellows is widely used in the aerospace field as a versatile part. As the pipeline of the gas and liquid fule of aircraft, multiply bellows plays a vital role in the performance of the aircraft fule transport system and its reuse can effectively save costs. The bellows needs to meet the increasingly strict requirement for strength, toughness and dynamic properties.In this thesis, aimed at the fuel transport corrugated pipeline of a type aircraft, the finite element software of ABAQUS is utilized to simulate the mechanical response of the bellows subjected to combined loads of pressure, shock, sweep and random vibration at high, room and low temperatures respectively in a working cycle. The computation is of considerable complexity and pretty expensive. On the basis of the previous simulation, fatigue life under dynamic condition and random vibration condition was predicted respectively using local stress-strain fatigue theory and Miner linear cumulative damage theory. The main results are achieved as below:(1) If an interior pressure of IMPa was applied, plastic regions were found occurring at the inside of the bellows, the joints of both ends, the weld joints of the bellows and the steel pipes.(2) An impact presure with maganitude of 1.7MPa resulted in the maximum of Mises stress exceeding the fracture limit at the weld joints of the multiply bellows with the steel pipes.(3) Response along the Z-direction to frequency sweep and/or random vibration is dominant and therefor the bellow is reliable(or prone) to lateral swinging.(4) The fatigue lifes of the pipeline under an interior pressure of IMPa and an impact presure with maganitude of 1.7MPa at room temperature are 57 times.In this thesis, a theoretical model including material nonlinearity and boundary nonlinearity is built. The corresponding numerical analysis method and scheme of prediction for fatigue life are proposed, which can provide the technical basis for practical application and engieering design.