Research On Frequency Domain Method Of Multiaxial Random Fatigue Based On The Critical Surface Method Grade

With the continuous increase of train running speed,the multi-axial random vibration load of vehicle suspension parts increases rapidly,and its multi-axis random vibration fatigue problem becomes more and more obvious.Therefore,it is more accurate and efficient to predict the multi-axial random vibration fatigue life of vehicle suspension parts.Important theoretical significance and engineering significance.This thesis focuses on the multi-axis frequency domain random vibration fatigue analysis method based on three stress criteria at the critical surface.First,combined with the three stress criteria,the maximum variance method,and the frequency domain fatigue life calculations on the critical interface,the MATLAB software is used to program a multi-axis frequency domain random vibration fatigue life calculation program based on three stress criteria on the critical interface.Secondly,using the cantilever beam as an example to evaluate the fatigue strength,the multi-axial loading fatigue conditions under different bandwidth excitations and first-order resonance excitations are analyzed based on three stress criteria of the critical interface.The fatigue excitation in the resonance region still influences the vibration fatigue life of the structure;the results obtained from the prediction of the fatigue life of the cantilever beam based on the maximum normal stress criterion at the critical surface and the maximum shear stress criterion at the critical surface are not different.Large,but the use of multi-axis frequency domain method based on the maximum normal stress and shear stress criterion at the critical surface to predict the fatigue life of the cantilever beam results smaller than the results obtained by the above two methods;at the same time,attention should also be paid to predicting the structural vibration fatigue life.The fatigue excitation on the left side of the resonance region.Then,the frequency domain excitation in Chapter 3 is converted into a time history by inverse Fourier transform.The more mature multiaxial time-domain method based on the McDiarmid stress criterion on the critical interface is used for the third chapter.The multi-axis frequency domain method is verified by the results of the calculation;it is found that under wide-band excitation,compared with the maximum normal stress criterion at the critical surface and the maximum shear stress criterion at the critical surface,two multi-axis frequency domain methods are based on the critical surface.The multi-axis frequency domain method of the maximum normal stress and shear stress criteria predicts the life of the structure more accurately;at the same time,the multi-axis frequency domain method can predict the fatigue life of the structure faster and more efficiently than the multi-axis time domain method.Finally,the uniaxial loading damage accumulation method used in the present project and the multi-axis frequency domain method based on the maximum normal stress and shear stress criterion at the critical interface are used to predict the fatigue life of the auxiliary mounting.The results show that the uniaxial loading damage accumulation method The multi-axis frequency domain method based on the maximum normal stress and shear stress criteria at the critical interface is used to calculate the auxiliary unit's danger unit at the bolt hole;multi-axis based on the maximum normal stress and shear stress criteria at the critical interface.The calculation of the fatigue life of the auxiliary mounting with the frequency domain method is less than that with the uniaxial loading da mage cumulative method.