Prediction Of Multiaxial Random Vibration Fatigue Life Based On Frequency Domain

Along with the process of industrialization, whether the vehicle of life or all kinds of machinery in the production, the main components are working under alternating loads.Fatigue failure seriously affects the normal use of them, random fatigue is one form of it.Because of the uncertainty of random fatigue loads, the complexity of structure, local structure is in a multiaxial stress state and each stress components are randomly changing. Estimation of random multiaxial fatigue life is a problem,especially,based on frequency domain random vibration prediction of multiaxial fatigue is very rare.So studying the frequency domain multiaxial random fatigue theory, predicting the fatigue life of structures under random loads has practical significance for new structure and in-service equipment.Firstly, after reviewing the vibration system,the distribution of peak and amplitude of stress response stochastic process and the multiaxial fatigue failure criterion, this paper makes the prediction method of multiaxial random vibration fatigue life integrat into a unified mathematical model.Then, the U-shaped groove notch specimen considered as the research object, its fatigue life is predicted in the acceleration power spectrum.After comparing different multiaxial random vibration fatigue life in the different stochastic processes including broadband and narrowband, the different fatigue failure evaluation criterion including the maximum principal stress criterion, the equivalent stress criterion, the critical surface criterion, the conclusion shows that 1) the fatigue life predicted by narrowband distributing is smaller than broadband distribution,2)the fatigue life predicted by the equivalent stress criteria is most conservative,the maximum principal stress criterion follows it,the fatigue life predicted by the critical surface criterion is most closest the test value.Finally,based on the practical angle,the fatigue life of the battery box under random acceleration power spectrum is predicted.The battery box model is established, analysis the modal gets the natural frequency and the vibration mode.Frequency response analysis has been done to obtain the stress response and the acceleration response and to check the strength of the battery box.Fatigue life analysis has been done to check the fatigue strength of the battery box and study the relationship among the fatigue life methods.In the last,it gets a similar conclusion of prediction fatigue life with U-shaped groove gap specimen.