Analysis Of Random Vibration Fatigue Of The Horizontal Stabilizer Actuator Structure

With the demand for higher speed and better mobility, modern aircraft are facing a more severe vibration environment. The horizontal stabilizer actuator is a critical structure in the longitudinal stability, but long-term vibration under random load may lead to the origination of fatigue crack in the components of the actuator, which will seriously affect the safety of aircraft flying. Based on random vibration theory and basic fatigue life theory, this paper predicts fatigue life of the horizontal stabilizer actuator under random excitation by means of the finite element method, and the simulated results are compared with the test result.First of all, some methods of estimating vibration fatigue life are introduced both in time domain and frequency domain, and corresponding ideas and computational steps are given in detail. Among them, this paper pays much attention on the frequency domain methods based on the power spectral density.Second, the finite element model of the horizontal stabilizer actuator is established and the critical region is determined according to satic strength analysis After having knowing about the intrinsic characteristics of the actuator, the frequency response analysis on the critical region is carried out, and then the power spectrum of the stress response can be obtained combined with that of the excitation.Finally, by using the time domain method along with the narrow band method based on the Bendat amplitude distribution model, the narrow band approximation methods depicted by Wirsching-Light formula and Tunna formula and the broad band method based on Dirlik amplitude distribution model, random vibration fatigue life of the critical region is estimated. The results indicate, the critical region predicted by the finite element analysis is identical with the the fatigue damage location in the vibration test, and it is of the same order of magnitude between the predicted fatigue life by the above methods and the tested one, which proves these methods are effective and feasible in estimating random vibration fatigue life of the horizontal stabilizer actuator. Among all frequency domain methods, the predicted life based on the narrow band approximation is closer to the test result. However, the fatigue life estimated by classic Dirlik model is even shorter than that of narrow band method. That shows the Dirlik model has its specific scope of application, which means it is not applicable to all kinds of non-narrow band random process.This paper studies the random vibration fatigue of the horizontal stabilizer actuator based on several estimation methods, and the main work and conclusions will provide important reference basis to improve the structure design and metal process.