| Summary: | 碩士 === 國立中央大學 === 機械工程學系 === 107 === To reduce the residual stress is an important issue of metal processing. A method, Vibration Stress Relief (VSR) was chosen here to reduce the residual stress. VSR is performed by applying cyclic load to the specimen. This method can release the residual stress and alter stress distribution due to the superposition of the residual stress and the cyclic external load. It is said that VSR is based on low cycle fatigue theorem. But the mechanism of reducing the stress is still unclear. This research numerically investigated the behavior of material SS400’s under cyclic loading by using finite element method. A cubic model, under a uni-axis, low cyclic fatigue load, was first considered for examining the material behavior of mean stress relaxation and cyclic creep. A specimen with a notch was then studied to understand the behavior due to stress concentration. Finally, a welded specimen, with residual stress, was studied to present the effect of VSR on a more realistic model. The numerical results show that the stress relief effect of applying cyclic load can be achieved if the amplitude of the load close to the yielding stress of the material.
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