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绪言目前一般认为,用断裂力学方法可以计算在规定工作应力下的临界缺陷尺寸。虽然线弹性断裂力学曾被用来估计破坏前可能发生大的塑性变形,但是线弹性断裂力学对塑性屈服并不考虑。我们认为:线弹性断裂力学对在那种情况下的结构整体给出一个很乐观的评价,因此必须对临界缺陷尺寸的估计予以修正。此外,由于许多构件承受循环载荷,故对在工作时疲劳裂纹由亚临界尺寸长大到临界尺寸的情况予以估计是很重要的。以前虽然在这方面做了工作,但是并未考虑缺陷接近临界尺寸时疲劳裂纹长大加速的情况。它之所以重要是因为在这种情况下疲劳裂纹长大的速度比在这一范围以下所测得的长大速度要高一个数量级。
Introduction At present it is generally believed that the fracture mechanics method can be used to calculate the critical defect size under the specified working stress. Although linear elastic fracture mechanics has been used to estimate the possible large plastic deformation before failure, linear elastic fracture mechanics does not consider plastic yield. We think that the linear elastic fracture mechanics gives a very optimistic assessment of the overall structure in that situation, and therefore the estimate of the critical defect size must be corrected. In addition, since many components are subject to cyclic loading, it is important to estimate the fatigue crack growth from subcritical size to critical dimension at work. Although previously done work in this area, but did not consider the defects close to the critical size fatigue crack growth accelerated. It is important because in this case the fatigue crack grows an order of magnitude faster than the growth rate measured below this range.