Critical review of the fatigue growth of short cracks |
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| Affiliation: | 1. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China;2. University of Chinese Academy of Sciences, Beijing 10049, China;3. School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China;4. State Key Labortory for Geomechanics & Deep Underground Engineering, China University of Mining & Technology, Xuzhou, 211116, China;5. Department of Civil Engineering, Monash University, Clayton, VIC 3800, Australia;1. Graduate School of Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka 940-2188, Japan;2. Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia (UTHM), Batu Pahat 86400, Johor, Malaysia;3. Department of Mechanical Engineering, Faculty of Engineering, University of Brawijaya, Malang 65145, Indonesia;4. Department of Mechanical Engineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka 940-2188, Japan;5. Department of System Safety, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka 940-2188, Japan;6. Toshiba Materials Co., Ltd., Isogo-ku, Yokohama 235-8522, Japan |
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| Abstract: | Retirement for cause (RFC) has become a popular design/analysis philosophy because it facilitates continued use of components which would otherwise be retired based on a safe life philosophy. RFC permits this continued service on the basis that service-induced damage tracked by periodic inspections will not develop to a critical size within a future operating interval. Successful implementation of RFC requires fracture mechanics technology to predict in-service growth behavior. Recent observations suggest that nonconservative estimates of crack growth rate (and therefore inspection interval) and critical flaw size arise when conventional linear elastic fracture mechanics (LEFM) is applied to predict the growth of physically small cracks. This paper summarizes the results of an extensive limited-circulation critical review of the phenomenology and mechanics of short crack growth with a view to identifying when this anomalous growth makes RFC analyses untenable in terms of LEFM. Factors which control the growth of short cracks are enumerated. It is shown for unnotched samples that the apparent effect may be traced to microcrack closure and the metallurgical, mechanical, and environmental transients which develop in the transition from initiation to steady-state growth. For notch samples the anomalous growth of cracks is traced to the inelastic action that develops a displacement-controlled notch field, which, contrary to LEFM analysis, dominates crack extension. Mechanics analyses relevant to characterizing the growth of short cracks are discussed. A crack tip opening displacement criterion is indicated to be appropriate. |
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