LIMITATIONS OF LINEAR ELASTIC FRACTURE MECHANICS IN RESPECT OF SMALL FATIGUE CRACKS AND MICROSTRUCTURE
作者:
Keiro Tokaji,
Takeshi Ogawa,
Yukio Harada,
Zenji Ando,
期刊:
Fatigue&Fracture of Engineering Materials&Structures
(WILEY Available online 1986)
卷期:
Volume 9,
issue 1
页码: 1-14
ISSN:8756-758X
年代: 1986
DOI:10.1111/j.1460-2695.1986.tb01207.x
出版商: Blackwell Publishing Ltd
数据来源: WILEY
摘要:
AbstractThe 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 3dare 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 applicati
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