Corrosion pit size distributions and fatigue lives - a study of the EIFS technique for fatigue design in the presence of corrosion
Corrosion pit size distributions and fatigue lives - a study of the EIFS technique for fatigue design in the presence of corrosion
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DOI：
10.1016/s0142-1123(03)00069-0
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发表时间：
2004-01-01
影响因子：
6
通讯作者：
Irving, PE
中科院分区：
文献类型：
--
作者：
Medved, JJ;Breton, M;Irving, PE
对含有3.18 mm半径半圆形缺口的Alclad 7475铝合金试样进行了人工和自然腐蚀环境试验，得到了缺口中坑深的分布范围为20 ~ 150pm。腐蚀暴露后，对20个试样进行恒幅和变幅加载。与未腐蚀样品相比，这些凹坑使疲劳寿命降低了40-50%。对长度大于50pm的裂纹的疲劳裂纹扩展速率的测量表明，腐蚀样品和未腐蚀样品的疲劳裂纹扩展速率相似。凹坑的作用是大大减少了裂纹扩展到100pm的循环次数。在几乎所有的试验中，坑穴处都发生了多次裂纹萌生，导致裂纹的不规则扩展，或出现裂纹屏蔽，或出现裂纹合并。利用寿命数据计算等效初始缺陷尺寸分布（EIFSD）。根据EIFS分布做出的寿命预测是非保守的。这些误差是由多次起裂和裂纹合并行为引起的。讨论了EIFS方法在点蚀设计中的适用性。(C) 2003 Elsevier Ltd.版权所有。
Samples of Alclad 7475 aluminium alloy containing a 3.18 mm radius semi-circular edge notch were subjected to artificial and natural corroding environments, producing a distribution of pit depths in the notch from 20 to 150 pm. After corrosion exposure, 20 samples were subjected to constant and variable amplitude loading. The pits reduced fatigue life by 40-50% when compared with lives of uncorroded samples. Measurements of fatigue crack growth rates on cracks greater than 50 pm in length showed similar rates in both corroded and uncorroded samples. The effect of the pits was to greatly reduce the number of cycles to grow the crack to 100 pm. Multiple crack initiation at pits occurred in almost all tests, resulting in irregular growth as either crack shielding or crack coalescence occurred. Equivalent initial flaw size distributions (EIFSD) were calculated from the life data. Life predictions made from the EIFS distributions were non-conservative. The errors are shown to result from multiple initiation and crack coalescence behaviour. The applicability of EIFS approaches to design against pitting corrosion is discussed. (C) 2003 Elsevier Ltd. All rights reserved.