9. Modification Optimization-Based Fatigue Life Analysis and Improvement of EMU Gear

This paper proposes an improved fatigue life analysis method for optimal design of EMU gear, which aims at the defects of traditional Miner fatigue cumulative damage theory. A fatigue life analysis method by modifying S–N curve and considering material difference is presented to improve the fatigue life of EMU gear based on shape modification optimization. A corrected method for stress amplitude, average stress, and S–N curve is proposed, which considers low stress cycle, material difference, and other factors. The fatigue life prediction of EMU gear is carried out by corrected S–N curve and transient dynamic analysis. Moreover, the gear modification technology combined with intelligent optimization method is adopted to investigate the approach of fatigue life analysis and improvement. It is found that the fatigue life analysis and improvement method proposed in this paper has higher prediction accuracy than the traditional method in most cases. It is concluded that the fatigue life is significantly improved by applying the proposed approach to the EMU gear. The results show that it is more corresponded to engineering practice by using the improved fatigue life analysis method than the traditional method. The function of stress and modification amount established by response surface method meets the requirement of precision. The fatigue life of EMU gear based on the intelligent algorithm for seeking the optimal modification amount is significantly improved compared with that before the modification.