Analysis On Vibration Fatigue Life Of Airplane Oil Pressure Reservoirs

Airplane oil pressure reservoirs are major fuel supplying parts of airplanes to fly upside down. Due to these alternating loadings, reservoirs are likely to cause fatigue fractures, result in fuel leakage and affect flight safety of airplanes. Therefore, when designs are completed,vibration endurance tests are required to verify their fatigue resistance. And the fixed-frequency vibration endurance test is commonly used in engineering.Subject of this paper originated from a certain Aircraft Industry(Group) Cooperation Ltd.When the vibration test, accumulator tank had serious problems in some frequency. The dynamic simulation and vibration fatigue life are analyzed, and Main tasks of this paper included:1, utilizing the pretreatment software to establish detailed finite element models of the vibration test system, including supporting arms, bondages, reservoirs, base, isolation rubber and the interconnected relationships; adopting the coupled acoustic-structural analysis to take into account influence of liquid fuels and establish acoustic-fluid models.2, extracting the structure of oil pressure reservoirs and modes of fluid-solid coupling via MSC.NASTRAN; illustrating that fluid has a significant influence on the structural dynamic characteristics by comparison; conducting fluid-solid coupling modal analysis on the system to obtain dynamic characteristics of the system; comparing them with the modal test results to verify accuracy of the finite element models.3, carrying out harmonic analysis on the coupling system in accordance with the test loading spectrum to obtain stress distribution of the vibration system and verify vibration strength of each component; finding out weak parts of oil pressure reservoirs to prepare for the subsequent fatigue analysis.4, in frequency domain, introducing fatigue software to accumulate damages caused by the 13 load cases of fixed-frequency vibration endurance tests to obtain fatigue damage of oil pressure reservoirs during a test cycle; predicting the actual service life of oil pressurereservoirs on the basis of the equivalent damage principle.The major innovation work is as follows:Calculating the damage of all modes by using special method and the simulation of fatigue life of the fixed-frequency vibration test are analyzed. At present,there is little research on the calculation of fixed-frequency vibration fatigue.