以有限元素模擬結果評估振動應力消除之效果

NCUIR > Engineering College > Graduate Institute of Mechanical Engineering > Electronic Thesis & Dissertation > Item 987654321/81643

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/81643

Title:	以有限元素模擬結果評估振動應力消除之效果
Authors:	陳宥任;Chen, You-Ren
Contributors:	機械工程學系
Keywords:	殘留應力;振動應力消除;低周疲勞
Date:	2019-07-26
Issue Date:	2019-09-03 16:34:57 (UTC+8)
Publisher:	國立中央大學
Abstract:	殘留應力的消除一直以來都是金屬加工領域的重要課題，隨著技術的發展，振動應力消除(Vibration stress relief, VSR)技術逐漸受到關注，它是一種基於低周疲勞理論，藉由材料內部殘留應力與外部負載疊加以產生塑性變形，來達到應力釋放、重新分布的目的。但其運作機制及可消除的應力量目前仍不甚明確。故本研究藉由有限元素模擬方法(Finite element method)來觀察材料SS400在低周疲勞之循環負載下的行為，以期能用模擬的方法預估施作振動應力消除的效果。本研究中首先採用1/8 立方體模型進行單軸拉伸之低周疲勞模擬，並搭配實驗結果，分別使用位移控制與力量控制來觀察材料的平均應力鬆弛 (Mean stress relaxation)與循環潛變行為(Cyclic creep)；接著使用具缺口(Notch)試片模型進行低周疲勞模擬來觀察材料在進行循環負載時，集中應力現象對材料行為的影響；最後利用具有殘留應力之銲接試片來進行彎曲實驗的低周疲勞模擬，以觀察振動應力消除的效果與應力分布的變化，模擬結果發現具有銲接殘留應力之試片的高應力區的應力重新分布，且整體的應力範圍也有下降，顯示出振動應力消除的效果。;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.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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