Fatigue Life Estimation of an Aircaft Engine Under Different Load Spectrums

Abstract

Aircraft engine components are subjected to variable amplitude load conditions usually they tend to experience fatigue damage. Many fatigue damage accumulation theories have been put forward to predict the fatigue lives of structure components. Under different load spectra, the aircraft engine has different working life. In this paper, based on the linear damage rule, the fatigue life of an aircraft engine was estimated by considering the load spectrum difference factor. According to one aircraft engine used for different load spectrums, the relationship between the load spectrum and the life is discussed. Moreover, the fatigue life of this engine used in A-type bomber is estimated based on the different load spectrum of the B-type bomber. A good agreement is found between the estimated results and real life data. Nomenclature s L stress level L n L corresponding numbers of load cycles at stress level L N L cycles to failure under the stress level L D fatigue damage S i corresponding load n i load cycles N i number of cycles R stress ratio X p peak load K t stress concentration factor a stress amplitude a0 stress amplitude when the mean value is 0 m mean stress m0 mean stress when the stress amplitude is 0 L f specified reliability coefficient V 2 high-pressure rotor speed S a symmetrical cyclic stress S a stress amplitude S m mean stress S b ultimate tensile strength

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