Research and Application of Random Vibration Fatigue Assessment System for Welded Structures in Railway Vehicle

Abstract

With the increasing speed of railway vehicle in China, the problem of fatigue failure in welded structures is becoming more and more serious. Because the frequency range of the external excitation load is wider, the structures are more likely to yield modal vibration, which will accelerates fatigue failure process of welded structures. Therefore, how to make it possible to take the effects of load frequency distribution on fatigue life into consideration when evaluating welded structures is a subject worth studying. Firstly, a new fatigue life prediction method of welded structures is proposed in this paper by the combination of the random vibration theory and the Structural Stress Method in ASME 2007 standard which is the most reliable fatigue life prediction method of welded structures so far. Fatigue life of welded structures can be calculated under frequency domain in this new method which is called Frequency Domain Structural Stress Method. Then, a random vibration fatigue evaluation system of railway vehicle welded structures based on this new method was built through C++ language with the cooperation of commercial software. This system make it possible to predict the fatigue life of welded structures at the product design stage of railway vehicle under random loads from measured or standards(can be force, displacement, velocity and acceleration data). An engineering application case of this system on the random vibration fatigue assessment of a car body lifting structure in an urban railway vehicle was carried out to verify the effectiveness of this system. This system can not only be used in the railway industry, but also in other industries.