LIMITATIONS OF LINEAR ELASTIC FRACTURE MECHANICS IN RESPECT OF SMALL FATIGUE CRACKS AND MICROSTRUCTURE
LIMITATIONS OF LINEAR ELASTIC FRACTURE MECHANICS IN RESPECT OF SMALL FATIGUE CRACKS AND MICROSTRUCTURE
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线性弹性断裂力学在小疲劳裂纹和微观结构方面的局限性
DOI：
10.1111/j.1460-2695.1986.tb01207.x
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发表时间：
1986
影响因子：
3.7
通讯作者：
Z. Ando
中科院分区：
文献类型：
--
作者：
K. Tokaji;T. Ogawa;Yukio Harada;Z. Ando
研究了一种低合金钢在旋转弯曲条件下的疲劳小裂纹扩展特性，该钢具有15 μm（细晶）和91 μm（粗晶）两种原始奥氏体晶粒尺寸。研究了晶界对裂纹扩展速率和裂纹纵横比的影响，并对线性弹性断裂力学（LEFM）适用的临界裂纹长度进行了评价。当表面裂纹长度小于3个晶粒直径（3d）时，裂纹扩展速率在晶界附近减小。纵横比也受到微观结构的影响，因此变化很大。超过3d的裂纹不受微观结构的影响，但它们的增长速度比基于LEFM的预期更快，直到它们的长度达到3d+ 150 μm。这种行为可能归因于小裂纹和大裂纹之间裂纹闭合的差异。如果裂纹闭合对小裂纹扩展的贡献可以通过实验或分析确定，则LEFM适用的临界裂纹长度为3d。但由于裂纹闭合性难以评价，工程应用中认为3d+ 150 μm为临界裂纹长度。
The growth characteristics of small fatigue cracks were investigated under rotary bending in a low alloy steel prepared with two prior austenite grain sizes of 15 μm (fine grain) and 91 μm (coarse grain). The influence of grain boundaries on crack growth rate and the crack aspect ratio was examined, and the critical crack length above which linear elastic fracture mechanics (LEFM) is applicable was evaluated for a growing small crack. When the surface crack length is shorter than three grain diameters (3d), crack growth rates decrease near the grain boundaries. Aspect ratios are also affected by the microstructure and thus vary widely. Cracks longer than 3d are not influenced by the microstructure, but they grow faster than would be expected based on LEFM until their lengths reach 3d+ 150 μm. This behaviour may be attributed to the difference in crack closure between small cracks and large cracks. If the contribution of crack closure to the growth of small cracks can be established experimentally or analytically, the critical crack length above which LEFM is applicable would be 3d. However, because it is difficult to evaluate crack closure, 3d+ 150 μm is considered to be the critical crack length for engineering applications.