| The problem of metro motor bogie frame’s fatigue performance cannot meet the full-life service safety and fatigue cracks appear in multiple welded parts,which frequently exposed on metro routes of some cities,has became an arduous challenge during the process of building China modern comprehensive transportation system.Therefore,it is of great scientific significance to carry out the fatigue damage analysis for the metro bogie frame,figure out the constitution and source of fatigue damage,enrich the prediction method of frame fatigue damage,so as to improve rail vehicle design standard system in China and further enhance the reliability of China rail transit equipment.Based on the dynamic stresses and loads-time data of motor bogie frame under service condition,the following research work is carried out in this paper:(1)Based on the measured dynamic stresses,axle box vertical acceleration(hereinafter referred to as"ABVA")and other measured data of bogie frame A and B,it is determined that rail corrugation existed both on test routes A and B,and the corrugation wavelengths are mainly concentrated in 100 mm,200 mm,300 mm and 400 mm.Besides,8-order wheel polygon is also determined,and the dynamic stress frequency whose change trend consistent with speed at the fatigue control locations(hereinafter referred to as"FCL")of frame is caused by polygon.(2)Distribution of fatigue damage of frame A,B and the influence of various factors on frame fatigue damage are analyzed.The results show that the main reasons for the fatigue damage accumulated rapidly are the vibration with frequency within 40～70 Hz,which are caused by rail corrugation and wheel polygon.The influence of rail corrugation is the largest,followed by the wheel polygon,and factors like rail joint,vehicle running state,speed and passenger capacity contribute very a little to frame fatigue damage.(3)Based on the measured dynamic stresses data of the FCL of frame A,the life reliability model of each location is established by the method of distribution fitting and hypothesis test.The analysis result shows that fatigue life of frame A is 110000 km under 99%reliability,and the remaining life is 5411000 km at the maximum probability density where reliability is 78.8%,suggested that frame A cannot meet the requirements of the whole designed life.(4)Combined with the measured loads of frame B and the load-strain transfer coefficients of each FCL,calculated stress σB of each part is calculated.Calculated and measured stress σB are divided in complete signals,quasi-static and dynamic three parts,then correspondence of equivalent stress amplitude(hereinafter referred to as "ESA"),time/frequency domain and correlation between the three parts of calculated and measured stress σB are compared respectively.The ratio of ESA of the two kinds of stresses is between 1.0～1.5,and the difference between the two kinds of stresses is mainly reflected in the small change range of stress and curved section corresponding to the island platform in or out of station,which has little influence on frame fatigue damage.Thus,the completeness of the measured load of frame B is verified.(5)Load-strain transfer coefficient of each FCL of frame A is calculated by simulation,then the time domain signal of the calculated stress σAa for each location on frame A is obtained.For the ESA ratio of quasi-static part between calculated stressσAa and measured stress σA,92%locations’ ratio are within 1.0～2.0,while ESA of all locations’ calculated stress σAa is less than measured stress σA for the dynamic part of two kind stresses.The results show that dynamic part of frame B’s measured loads cannot be applied to fatigue damage prediction for frame A directly.(6)Based on the amplitude-frequency,phase-frequency response curves of frame-motor system with single-degree-freedom and frame A’s in-position modal frequency,the dynamic part of motor vertical loads is adjusted,and applied to acquire calculated stress σAb of each location of frame A.ESA of calculated stress σAb can cover measured stress σA.Furthermore,based on the amplitude characteristic of corrugation in main frequency band of routes A and B,the dynamic part of motor vertical loads is adjusted again,and calculated stress σAc is obtained by the same method.ESA ratio range between each locations’ calculated stress σAc and measured stress σA is 1.0～2.0.It shows that the method of adjusting the dynamic part of motor vertical loads,which is proposed in this paper,is effective and can be used to predict fatigue damage of other routes’ other frames after adjusting motor vertical loads.It provides an effective theoretical and methodological support for the establishment of fatigue damage prediction load conditions of frame under multiple routes based on the measured load samples.84 Figures,28 Tables,103 References... |
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