| Monorail is a new type of transportation in China. However as the fatigue problem is beginning to come out, it’s more and more important to analysis the fatigue life of this new kind of transportation. Because the monorail is different from other traditional rail transit, its structure is more complex, and the original method to analysis the fatigue life is not fit any more. Therefore this article based on the theory of vibration and the standards of FKM (which is a strict standard to analysis the fatigue life of components) work on predicting the monorail’s car body’s fatigue life.Firstly, this article introduce how to carry out the excitation from the center pivot, air spring and couple by numerical integration and finite element model and get the external load of the car body.Secondly, I build a finite element model of car body to get the modal by ansys software, With the result of the modal analysis, this article get the dangerous frequence which may cause resonance. After that, I get the function of response in frequency domain which is also called harmonic response by different load.Thirdly, I transform the load data to the frequency domain by FFT. With the result of the function of response, I can get the response of the dangerous point.Finally, I predict the fatigue life of the dangerous point by the standard of FKM. In this case, I use the method which is used in multi - axial stress to get a accurater result. From this article, I can get the conclusion that this method of vibration fatigue analysis is convinced after comparing the fatigue life in real line text with the result of vibration simulation analysis as the error is only 8%-20% when the original method’s error is over 100%.This article has support the rationality of vibration fatigue analysis in the area of aluminium alloy car body both in theory and reality. |
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