Fatigue Life Analysis Of Random Vibration For Rolling Stock Equipment

The process of traditional fatigue analysis methods is that, firstly, get the stress-time history by experiments, then, convert it to various stress cycles, finally, get the fatigue life with appropriate fatigue cumulative damage rule. With the constantly development of computer technology and computational mechanics, fatigue analysis methods based on finite element technology is gradually been adopted. This makes it possible that the analysis of static, dynamic strength, and prediction of fatigue life, which can evaluate the products fast and directly during their project design. That is of great significance for guiding the design, manufacture, maintenance and management of the equipment, and preventing the occurrence of fatigue fracture failure.The time domain simulation methods, including quasi-static methods and transient surveying method are summarized in this article. In order to analyse the advantages and disadvantages, and the scope of the two methods, these two approaches are adopted to get the fatigue life of the cantilever beam which has a u-shaped slot gap and compare it with the test result in Wang Mingzhu’s Ph.D. thesis "Research on Life Analysis Method for Structure Vibration Fatigue".The result show that, when structural dynamic characteristics significantly influence the fatigue life of components the result is not true by using the quasi-static simulation method, and transient surveying method can simulate random vibration fatigue life more preferably, but the calculation of transient method is so huge, and the requirement on the computer is so high, that it is difficult to get the application in engineering.The empirical formula and theoretical model of frequency-domain method are analyzed and summarized, which can ensure the probability density function of rain flow circulation by the power spectral density function the structural response. The narrowband method and Dirlik method are compared by using the experiment result as the testing method. It can be found by the comparison that, the error by using narrowband method to analyze the broadband random process is bigger, the result of Dirlik method is in good agreement with the test result, and and with the increase in load power spectral bandwidth, the Dirlik method and transient method calculation deviation becomes smaller.The fatigue life analysis of random vibration for the U-shaped slot gap cantilever structure is the theoretical and practical basis for the random vibration fatigue life prediction of locomotive hanging equipment.Finally, The frequency domain method for random vibration fatigue life is introduced into the fatigue life prediction of rolling stock equipment named dirt box structure. According to TB/T3058-2002, it’s fatigue load spectrum is taken as level Class1, Class A. Nastran software is used to analysis its random vibration response, and then nsoft fatigue simulation software is used to predict fatigue life by combining with Dirlik guidelines and material S-N curve.