Random Vibration Fatigue Life Analysis Of Aircraft Typical Structures

Aircrafts always produce or suffer extremely complex random vibration excitation in the process of taking off, cruising and landing, which will lead to many structural vibration problems concerned with personnel comfort, structural reliability, durability and vibration fatigue etc. So it is of great significance to predict the aviation typical structures’ fatigue life under random vibration excitation in the process of design, manufacture, use and maintenance etc.Starting from the structural fatigue problems, this thesis uses the methods of theoretical analysis, programming, experimental study, simulation comparison etc. to make systematic and in-depth research about the problems on structural random vibration fatigue life analysis.Firstly, this thesis estabilished the finite element model of one typical aircraft stiffened panel and used five frequency domain analysis methods to make life prediction based on the results of finite element analysis.Then a new way of randon vibration fatigue accelerated test design based on frequency domain methods was proposed.Then, this thesis peformed an example to test and compare the characteristics of two kinds of mostly used time domain simulation methods which are named Trigonometric Series Method and Inverse Fourier Transform Method. Because of better performance, the time domain simulation results from the Inverse Fourier Transform Method were adopted and the Rain Flow Cycle Counting Method was applied to predict the above aircraft stiffened panel’s fatigue life by using Sample Method. After that, the results of the time domain and frequency domain analysis method were compared.Finally, this thesis performed the modal analysis test and broad-band random vibration fatigue test of one 7075-T6 aluminum alloy structure and got the fatigue life value of each test piece. According to the results from the tests, correction of the finite element model was conducted. Then, based on the results from finite element analysis, both the frquency domain methods and the time domain method were used to predict each test piece’s fatigue life. After that, the results from stimulation and test were compared.