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題 名 | 具平均應力金屬疲勞壽限預估模式之探討=The Effect of Mean Stress on the Fatigue Reliability Evaluation |
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作 者 | 王國雄; 沈盈志; 許芳勳; | 書刊名 | 力學 |
卷 期 | 13:3 1997.09[民86.09] |
頁 次 | 頁245-254 |
分類號 | 440.2 |
關鍵詞 | 疲勞可靠度模式; 平均應力; 負荷調整; 疲勞阻抗; Fatigue reliability model; Mean stress; Loading adjustment; Fatigue resistance; |
語 文 | 中文(Chinese) |
中文摘要 | 本文主要探討平均應力對可靠度退化現象與疲勞壽限的影響:並利用代數型動態 可靠度模式處理負荷調整問題。該模式之可靠度與失效率函數成代數關係,其退化行為受控 於內在退化係數 A 及程序退化係數 A �窗F其中程序退化係數為交變應力與平均應力的函數 ,而平均應力亦會影響內在退化係數。將預估結果與另組數據比較,發現本文之預估方法, 基為接近該數據之平均曲線; 其 Sm/Su 對應 Sa/Se 之關係曲線, 約落於 Goodman 與 Gerber 兩關係曲線之間。 由於 AE 動態可靠度模式具有累積內在損傷的特性,非常適合運 用於負荷調整之可靠度預估及壽限預估上。本文針對 " 高應力到低應力 " 的負荷調整程序 ,定義一機件疲勞阻抗 Dp,依據需求條件, 最大化該疲勞阻抗,以獲得一最適之負荷調整 方案。結果發現,當可靠度退化至一定程度 (本文實例顯示該值約為 0.65 左右 ),即不無 需再調降其負荷。而執行負荷調整時,以調降交變應力,較能提高該機件之疲勞壽限與疲勞 阻抗。 |
英文摘要 | This paper extends the previous studies of fatigue reliability when the mean stress is considered. Based on the experience in the modeling of dynamic re-liability, an algebraic-dependent reliability equation model (AE model) is taken to depict the fatigue reli-ability and life in this situation. The model concerns with two decay factors. One is so-called imbedded decay factor which deals with the intrinsic weakness of mechanical element. The other is called process-dependent decay factor which relates to the loading process. The process-dependent decay factor de-pends on the extrinsic demand, including alternating stress and mean stress. Comparing the estimated results with experimental data, it is found that the proposed approach presents the relation close to the mean of experimental data, and shown between Goodman's and Gerber's curves. The cumulation of weakness, which increases dur-ing the process, can be shown in the AE model,thus this model can easily be extended to the case of varied amplitude loading. Furthermore, a fatigue resistance Dp is defined to discuss the loading ad-justment problem. An optimal loading process can be programmed by achieving the fatigue resistance Dp as larger as possible under prescribed constraints about the amplitude reduced range. The results show that it is not worth to adjust the loading as the reliability goes down to a certain value. It also show that the adjustment would tune the alternating stress level rather than the mean stress. |
本系統中英文摘要資訊取自各篇刊載內容。