Research On The Relationship Between The P2 Force Resonance Of Subway Common Short Sleeper And The Life Of Primary Coil Springs

With the rapid development of Chinese economy,more and more cities begin to build subway and other urban rail transit.With the advantages of safety,punctuality,convenience and large passenger volume,subway has become an important means of transportation for many cities.On the subway,wheel-rail excitation is an important source of excitation for vehicle track vibration and component damage.For example,the P2 force resonance is an important form of wheel-rail excitation.Because its frequency range is easily transferred from the wheel-rail interface to vehicle parts,it has an important impact on the damage of vehicle parts.Therefore,it is necessary to conduct research on the damage of vehicle components caused by the P2 force resonance.This thesis focus on the frequent fracture of primary coil springs in the operation process of domestic subway vehicles,research on the impact P2 force resonance of different track structures have on the life-span of primary coil springs.Based on the test data and spring fatigue life prediction model,this thesis studies the impact ordinary short sleeper solid bed have on life-span of primary coil springs,compared with relevant results of 12 mm and 18 mm elastic short sleeper solid bed.The reason why the life of primary coil springs is too short is clarified: the frequency of P2 force resonance on ordinary short sleeper solid bed and the through frequency of specific wavelength on rail surface irregularity which is caused by the P2 force resonance on ordinary short sleeper solid bed are both in accordance with the inherent frequency of primary coil springs,which lead to the resonance of primary coil springs during operation,seriously shorten service life of primary coil springs.According to the research conclusion and field test data,the measures to prolong the life of primary coil springs are studied,which provides the basis for the metro operation and maintenance department to take measures to slow down the spring fracture.The main contents of this thesis is as follows:1.This thesis summarizes the domestic and foreign research achievements on the P2 force resonance,the fracture of primary coil springs and the prediction of fatigue life,and puts forward the research route on the frequent fracture of primary coil springs in certain subway in China.2.This thesis introduces the field test of the running state of a certain subway vehicle and line in China,including the test of rail surface irregularity,vibration acceleration test of vehicle parts,dynamic stress test of primary coil springs,and hammering test of primary coil springs.By analyzing the test results of the spring stress in the running of the train,it is found that the spring stress amplitude in the running of the ordinary short sleeper solid bed is obviously larger than that in the 12 mm elastic short sleeper solid bed and the 18 mm elastic short sleeper solid bed.According to the test of hammering test of primary coil springs we can confirm that the inherent frequency of the primary coil springs in the installation state is around 60 Hz.3.Through the comparative analysis of axle box acceleration and rail surface irregularity data,combining with the theoretical calculation results of P2 force resonance frequency,the relationship between rail surface irregularity and P2 force resonance of different track structures in this line is studied.The P2 force resonance frequencies of ordinary short sleeper solid bed,12 mm elastic short sleeper solid bed and 18 mm elastic short sleeper solid bed were respectively around 60 Hz,38 Hz and 34 Hz.The test results were consistent with the theoretical calculation results.P2 force resonance frequency of each section is consistent with the through frequency of track surface irregularity,so it can be concluded that P2 force resonance is an important cause of specific wavelength irregularity on rail surface.4.Based on the comparison and analysis of the spring stress test data,the relationship between the P2 force resonance of different track structures in this subway line and the spring stress of primary coil springs is studied.The spring stress characteristic frequencies of ordinary short sleeper solid bed,12 mm elastic short sleeper solid bed and 18 mm elastic short sleeper solid bed were respectively around 60 Hz,38 Hz and 34 Hz.The spring stress characteristic frequency in the ordinary short sleeper solid bed is consistent with the spring inherent frequency,both of which are around 60 Hz,and the spring stress amplitude also increases obviously,so we summarize that primary coil springs generate resonance.Based on the theory of Miner linear cumulative damage,primary coil spring fatigue life prediction model was established.The measured dynamic stress of the spring was taken as the input of the model,and the average life of the field broken spring was taken as the correction coefficient to estimate the fatigue life of the spring.We also studied the impact P2 force resonance of a series of different track structure have on the fatigue life of primary coil spring based on the above model.We confirm that P2 force resonance on ordinary short sleeper solid bed and the through frequency of specific wavelength on rail surface irregularity which is caused by the P2 force resonance on ordinary short sleeper solid bed are important causes of spring resonance and spring failure.5.Based on the established prediction model of spring fatigue life and field test data,various measures to prolong the fatigue life of primary coil spring are studied.Through the evaluation and analysis of the field implementation effect,it is clear that grinding and adjusting speed are methods that can effectively extend the service life of a primary coil spring.The optimization scope and limit value of the improvement measures are put forward to provide the basis for the related improvement work of subway operation and maintenance department.