This paper presents design optimization of an electromagnetic vibration energy harvester to improve durability and increase life cycle. The energy harvester discussed in this paper has been developed by the Korean Railroad Research Institute, as a maintenance-free power supply for a wireless sensor module that monitors rail bogie axles and bearings. Our research team realized a durability issue in the leaf spring in this harvester because of high stress concentration and the corresponding fatigue failure when the harvester experiences high impact loading in rail operation. The topology optimization method has been applied in this research to design the shape of the leaf spring with a lower stress concentration magnitude while satisfying the multiple functional requirements on vibration amplitude and natural frequency. For fast and effective design search, we firstly identified several initial models from literature. These models have been carefully chosen to minimize any unnecessary parasitic motions. The topology optimization is then applied to produce the new leaf spring structure. The results of this research showed that topology optimization method could reduce the magnitude of stress concentration while satisfying required vibration amplitude and natural frequency of the spring structure.

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