| In order to ensure the safety and reliability of rail vehicles,a variety of functional equipments are generally installed at the end of bogie.The equipment structure has long been in the random vibration environment which deteriorates with the increasing speed,and a large number of random vibration fatigue failures have occurred,which have seriously affected the operating safety.There are two methods for fatigue life evaluation of random vibration,which are time domain method and frequency domain method respectively.Compared with the traditional time domain method,the frequency domain method is more intuitive,convenient and fast.Therefore,this thesis mainly studied the application of the frequency domain life evaluation method in the random vibration fatigue evaluation of the railway vehicle bogie accessory equipment.The following research work has been carried out in this thesis:(1)The theory and method of fatigue life time domain method and frequency domain method for random vibration are summarized.Five frequency-domain models(Rayleigh,Dirlik,Zhao–Baker,Weibull and Lalanne models)are used to study the influence of bandwidth coefficient,center frequency and PSD spectrum value on the estimation results of the model based on band-limited white noise spectrum.The influence of the root mean square ratio and the center frequency distance on estimation results are studied based on the bimodal spectrum,which provides a theoretical basis for proposing a new frequency domain method model and checking the fatigue life of the bogie accessory equipment in the following thesis.(2)Based on the IEC 61373 standard,several groups of band-limited white noise stress power spectra with different spectral parameters are established within the main bearing frequency range of the bogie accessory equipment,and the corresponding rain flow amplitude probability density is obtained by using the inverse Fourier transform method and the rain flow counting method.The weighted combination function model of Rayleigh and Weibull distribution is selected to fit the rain flow counting results of each group,and the relationships between the spectral parameters and the probability density of stress amplitude are studied.Finally,a frequency domain method model is proposed,which mainly considers the bandwidth of power spectrum and the root mean square value.(3)A random vibration fatigue test is designed for typical test pieces,and the finite element model of the test piece is established,and the random vibration fatigue test is guided by the results of modal analysis and random vibration analysis.The test life results are compared with the results calculated by frequency domain method,and the calculation accuracy of the common frequency domain method model in practical engineering is analyzed,and the reliability of the model proposed in this thesis is verified.The results show that the calculation results of all frequency domain method models tend to be conservative,the calculation errors of Zhao–Baker model,Dirlik model and Tovo-Benasciutti correction coefficient method are relatively small.Among them,the frequency domain method model proposed in this thesis has the smallest calculation error and high reliability.(4)The finite element model of antenna beam structure,a typical accessory device of bogie,is established.According to the acceptance criteria of rail vehicle bogies and their accessories in the IEC 61373 standard,the random vibration fatigue strength of antenna beam structure was checked by frequency domain method.The results show that the circumferential butt weld area on the antenna beam is relatively safe,and the T-shaped weld area has the potential of fatigue damage during vehicle operation.Therefore,the weld structure needs to be improved. |
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