Comparative Analysis Of Dynamic Responses Of The Typical Structure Under Uniaxial And Triaxial Random Vibrations

The vibration test is to identify whether the structure or equipment can withstand vibration environments, that is, the test is a necessary measure to ensure the structural integrity and the accuracy of instrument under the physical environments and the progress of equipment performing. The traditional vibration test uses uniaxis vibration testing method, and in order to approximate triaxis vibration test,three orthogonal axes vibration testes are performed in sequence. With the increasing complexity and reliability of aerospace products, it is more and more important to simulate the real environment. It was proved that triaxial vibration test can make up for the failures that the uniaxis vibration test can’t. Therefore, it is necessary to carry out the research on the triaxial vibration test.A comparative analysis about the dynamic response of the cabin structure under uniaxial and triaxial random vibration is studied in this thesis, including the comparative analysis of accelerations, comparative analysis of stresses, the comparative analysis of fatigue life(fatigue cumulative damage),which is aimed at effectively improving uniaxial testing quality as well as putting triaxis vibration testing into widely application.1. A study of the basic theories of the inherent characteristics and random vibration response is made, which mainly studied the relationship between the random excitation and response in the frequency domain. The structural finite element simulation technology is discussed, as well as the reliability of Ansys Workbench simulation results are demonstrated by two examples,which lays the theoretical foundation for the cabin structure finite element analysis(FEA) in subsequent chapters.2. The differences of the structure dynamic responses under uni-axial and triaxial random vibration are comparated; and the stress response and acceleration response of cantilever structure under uniaxial and triaxial random vibration are simulated through the finite element software Ansys Workbench. Thereby, the cantilever’s dynamic response differences under the two conditions is summaried, so that to acquaint the different effects of uniaxial、triaxial random vibration test.3. The repairing and simplifying of the CAD/CAE model of cabin structure is studied, then according to the actual connection of cabin structure, the contact type and the restricted locations of cabin structure are set up. The natural frequencies and vibration modes of the cabin structure are determined through the modal analysis, as well as easily induced vibration parts. Also the uniaxial vibration and triaxial vibration dynamic responses of cabin structure are analyzed under the given experimental conditions, and especially focus on the relationship of cabin structure’s acceleration and stress responses under the two conditions.4. A calculation method of random vibration fatigue is put forward. The inherent characteristics and the dynamic response of the cantilever are simulated through the finite element analysis software, which fit the experimental results well. Then the fatigue life of cantilever is calculated according to simulation results, and the result is a bit conservative, but it meets the engineering requirements. Also the fatigue lifes of cabin structure under uniaxial and triaxial random vibration are calculated, and the relationship of the fatigue damages caused by triaxial random vibration and uniaxial random vibration is studied.