臺灣博碩士論文加值系統

摘要

材料在平均應力的周次負載作用後其周次行為與疲勞壽命會有很大改變。因此本文最主要是研究430不鏽鋼材料在具有平均應力的周次負載作用下，其平均應力對430不鏽鋼材料之周次行為與疲勞壽命的影響。對此本研究將把實驗分為兩種型式第一種型式將對430不鏽鋼做一系列完全反覆( Mpa)高周次疲勞實驗，其控制應力振幅為320MPa到 380MPa 等。另一種疲勞實驗為具有平均應力40 MPa的高周次疲勞實驗，而控制應力振幅為300 MPa 到360MPa等。最後再將其實驗結果所得到的實驗數據進行分析比較，並在各章節分別探討平均應力對430不鏽鋼材料的周次行為及疲勞壽命的影響。而由實驗結果指出430不鏽鋼材料在具及不具平均應力的周次負載下會產生周次潛變(Cyclic Creep)，且在平均應力的影響下材料會有軟化現象。至於在疲勞壽命方面，由實驗數據顯現出平均應力對疲勞壽命有明顯的影響，另外本研究也將應用不同疲勞壽命的評估方法，來評估受測材料在平均應力影響下的疲勞壽命，並將由不同評估方法所得到的預估壽命值與實驗壽命值進行比較，以了解其評估能力，最後為了更進一步確定其評估的準確度，因此將利用統計公式算出其統計比較值 ，以確定這些壽命評估方法的評估能力。

Abstract
In this paper, the effect of the mean stress on ratchetting process in 430 Stainless Steel was examined by performing a series of cyclic loading tests with or without mean stress level on the tested material. Based on the experimental results from the fully tensile-compression cyclic loading tests, it is found that a compressive cyclic creep occurs in all applied cases the tested material. Therefore, the tested material is anisotropic in both tension and compression. Furthermore, for the tested material with mean stress effect, cyclic creep can also be found and the direction of creep deformation is always same to that of the given mean stress. Exploring the effects of the tensile mean stress on the stable stress-strain response, this paper has been focused on those items. They are the strain range, , plastic strain range, , and plastic strain energy density, at half-life. Experimental results show that the material with tensile mean stress had a higher response when the applied stress amplitude range was increased. In observation the effects of tensile mean stress on the fatigue, it is found that the effect of the tensile pre-strain is to reduce the cycles to failure. Moreover, the damage parameter based on the plastic strain energy in tension, , can produce satisfactory life prediction results for 430 Stainless Steel under a asymmetric cyclic loading condition.

圖目錄... Ⅲ
表目錄... Ⅳ
第一章 前言.... 1
第二章 文獻回顧..3
第三章 實驗內容與設備..6
3-1 實驗材料介紹..6
3-2 實驗設備介紹..8
3-3 實驗內容與實驗參數設定....9
3-4 周次負載下試片破壞型態觀察... 11
第四章 平均應力對430不鏽鋼材料周次行為影響分析....13
4-1 平均應力對430不鏽鋼材料暫態周次行為影響....13
4-1-1 周次潛變曲線影響分析....14
4-1-2 周次應變振幅曲線影響分析..... 17
4-2 平均應力對430不鏽鋼材料穩態周次行為的影響.....19
第五章 平均應力對430不鏽鋼材料疲勞壽命的影響及預測....23
5-1 疲勞壽命周次定義及實驗結果....23
5-2 430不鏽鋼材料疲勞壽命曲線的建立...25
5-3 平均應力對430不鏽鋼材料疲勞壽命的影響...27
5-4 應用等壽命(constant-life curve)方法預估在平均應力 響下疲勞壽命..29
5-5 430不鏽鋼材料在平均應力影響下疲勞壽命的評估...33
5-5-1 以SWT為損傷參數預估430不鏽鋼材料在平均應力影響下疲 勞壽命...33
5-5-2 以張力狀態下穩態塑性能密度 為損傷參數預估在
平均應力影響下430不鏽鋼材料疲勞壽命..36
5-6 預估壽命準確性分析… 38
第六章 結論..... 40
第七章 參考文獻..44
圖............47
表...........96
符號說明.....100

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