Study On Fatigue Damage Of High-Speed EMU Frame Based On Working Condition Identification

At the end of 2018,the operating mileage of China's high-speed railways has approached 28,000 km.Due to the large-scale operation of the "Renaissance" EMU,China's current active EMUs have nearly 3,000 groups.With the continuous investment of new lines and new EMUs,as well as the continuous improvement of the running speed and the ride comfort requirements,it is particularly important to study the safety and reliability of vehicle operation.The welded frame is the key structure of the running gear of the EMU,and it is an important guarantee for the safe and reliable use of the whole vehicle.In recent years,research on the fatigue of the frame under the load system such as traction and braking,and the damage law of the key parts of the frame through long-term stress test have achieved initial results,but for different line conditions and working conditions.Research on the impact of frame bearing and damage state remains to be deepened.Based on the above background,this thesis studies the classification and identification methods of high-speed railway line conditionsd.Based on the measured data of the line,this paper calculates the coupling relationship between various operating conditions and structural fatigue damage,and finally makes a more accurate prediction of the structural damage through the working condition identification data.The main research contents are as follows:1.Starting from the actual requirements of sensor data processing from condition identification and damage analysis,combined with the actual data of gyroscope and resistance strain gauge,the theory and application of classical filtering,wavelet transform and Hilbert-Huang transform are studied.The essential characteristics of each internal modal function obtained by empirical mode decomposition of the acceleration signal are recognized,so that the recognition accuracy is greatly improved in the case of the condition recognition based on the radius of curvature.2.Statistical analysis is carried out on the typical operating conditions of the existing high-speed railways in China.It is found that the regularity and difference between different lines.And the difference in the distribution of working conditions may be the fundamental reason for differences in frame damage when using different lines.According to the working principle and measurement accuracy of the micromachined gyroscope,the identification scheme of curve and turnout based on radius of curvature is proposed.In the recognition of the radius overlap range,based on the Hilbert-Huang transform theory,the energy entropy of the internal modal function of the acceleration is used to make a more accurate division of curve and turnout.3.According to the characteristics of the pressure change,the scheme makes a judgment on meeting and pass tunnel.After analyzing the large air pressure test data of the EMU equipment cabin,it is found that the regular expression of the air pressure value under the above conditions can be used as the basis for identification.After meeting and pass tunnel data are extracted separately,the threshold condition discrimination method based on the support vector machine theory is given.After analyzing the recognition effect of the scheme,the tunnel identification scheme under the cooperation of GPS signals is supplemented,and the recognition accuracy is comprehensively improved.Summarize the judgment basis and process of various working conditions,and establish the basic EMU working condition recognition theory.4.The distribution law of dynamic stress test data is studied.The fitting scheme of three-parameter Weibull distribution is given.Based on various series selection theory,the number of statistical groupings of dynamic stress data is studied.According to the S-N curve of the material and the Miner damage rule,the calculation formula of the equivalent stress is derived,and the relationship between the distribution parameters and the equivalent stress is discussed by using the measured data of the frame.5.Statistics on the dynamic stress test data of a large number of frame with same working conditions and routing,it is found that the discreteness of the dynamic stress test results is ubiquitous.In the aspect of investigating the outliers of dynamic stress samples,based on the basic theory of error analysis,a correction algorithm for the quartile method of small samples is proposed.The data of different routing of the 350km/h speed class EMU frame is used to conduct the distribution test to determine the distribution law.The differences in the equivalent stress distribution of the measuring points under different operating conditions are studied in depth,revealing the correlation between the equivalent stress distribution parameters and the degree of fatigue damage.The stress equivalent method based on the idea of probability and damage consistency is given,which makes the fatigue damage assessment of the frame more scientific and accurate,and has sufficient theoretical basis.6.The equivalent stress state of the frame in various single working conditions such as straight line,curve,meeting and tunnel is given.The relationship between different working conditions and the damage of different positions of the frame is analyzed briefly.For the multi-condition superposition problem,the BP neural network inputs a large number of single condition and multi-condition status and frame response output,and trains the network to give a more accurate frame state when the working conditions is superimposed.Finally,the condition identification and division of a large number of lines are carried out,and the damage state of the frame is given by the identified working condition data,and compared with the dynamic stress data of the full routing test,and the effects of condition identification and damage assessment are comprehensively analyzed.The conclusions of this thesis provide a theoretical basis for the establishment of further refined load spectrum,and also provide reference for the design of high-speed railway lines with reference to vehicle damage law.At the same time,a new prediction theory is given for the stress states of various EMUs on the new line,and the dynamic stress test results of the frame on different routings are well estimated,which has certain theoretical guiding significance and engineering practical value.