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題名 | 缺陷尺村和力學性能的關係=Relation between Defect Size and Mechanics Properties |
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作者姓名(中文) | 胡志忠; 曹淑珍; | 書刊名 | 材料科學 |
卷期 | 29:3 1997.09[民86.09] |
頁次 | 頁177-184 |
分類號 | 440.2 |
關鍵詞 | 疲勞強度; 硬度; 屈強比; 硬化指數; 非損傷裂紋; Fatigue strength; Hardness; Hardening exponent; Non-damage crack; |
語文 | 中文(Chinese) |
中文摘要 | 利用顯微缺陷或短裂紋的斷裂力學關係以及光棒疲勞極限與強度和硬度等的關 係,得到不降低疲勞強度的最大非損傷缺陷尺寸,或者稱為臨界裂紋尺寸,是由硬度和硬化 指數所控制。在相同的強度或硬度下,屈強比越小或硬化指數越大,材料內的這種缺陷越大 ,疲勞強度越低。強度或硬度越高,臨界滑移帶裂紋尺寸越小。對高強鋼,臨界缺陷尺寸的 變化範圍是隨著強度的升高而增大。本文提出了顯微缺陷的疲勞應力集中係數等於滑移開裂 的疲勞強度和實測的疲勞強度之比,對中低強度鋼,其值接近於 1;對高強度鋼其值大於 1 。該係數越大材料對缺口越敏感。最後給 X 了在疲勞門檻區附近,顯微裂紋的萌生和擴展 機制圖,該圖能夠把材料的基本力學性能(如強度、硬度和硬化指數),近疲勞門檻區短裂 紋萌生的缺陷類型和尺寸及其擴展機制,以及顯微組織短裂紋尺寸或應力同性能的關係等有 機的聯繫起來。 |
英文摘要 | By means of the relation of the fracture mechanics for micro defect or short crack, and the relation between the plain fatigue limit and the strength or hardness, it is obtained that the largest defect size of non-damaging plain fatigue limit, or called as critical defect size, is controlled by the hardness and hardening exponent. At the same strength or hardness, the higher the hardening exponent is or the lower the yield/tensile ratio is, the larger the critical detect size is. The higher the st ength or hardness is, the smaller the critical slip hand crack size is. For the high strength steel, the change range of critical defect size is increasing with the strength or hardness. It is proposed that the fatigue stress concentration factor for a material with micro defect is equal to the ratio of the plain fatigue limit for slip cracking model to the measuring plain fatigue limit. This factor is near to 1 for low and middle strength steel, and is more than 1 for high strength steel. The larger this f actor is, the more sensitive for notch the material is. Lastly, the initiation and propagation mechanism map for short crack at the condition of the fatigue threshold is given, which can connect organically the basic mechanical behaviours (e.g. yield/tensile ratio, hardness and hardening exponent etc), the type of defect and size of crack initiations, and the propagation mechanism at the region near to the short crack fatigue threshold, as well as the relation between the microstructure short crack and the mechanics properties. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。