Study on the Fatigue Reliability of Structural Members under Random LOading.

本课题提出了一种采用多缺口试样的疲劳试验方法，通过少量的疲劳试验来估计疲劳裂纹起裂寿命的分布函数。重点是有效利用单个试件提供的疲劳数据，减少疲劳试验所需的试件数量。试验结果表明，两个或三个多缺口试样足以确定实际水平裂纹起裂寿命的分布函数。即使仅用一个试样进行疲劳试验，也可以大致估计其分布的统计特性。由于在试验过程中产生的疲劳裂纹的影响不能得到严格的处理，本文提出的方法可能不适用于裂纹起裂寿命的精确估计。然而，由于该方法可以大大减少试样的数量，因此在长寿命范围内的疲劳试验中仍被认为是实用和有用的。

This project presents a fatigue testing method using a multi-notched test specimen for the purpose of estimating the distribution function of fatigue crack initiation life by a small number of fatigue tests. Emphasis is put on the effective use of the fatigue data provided by one test specimen and to decrease the number of specimens required in the fatigue tests. The experimental results indicate that two or three multi-notched specimens are enough to determine the distribution function of crack initiation life of practical level. And even from the fatigue test using only one specimen, the statistical properties of the distribution can be roughly estimated.The method presented herein may not be appropriate for the precise estimation of the crack initiation life, decause the effect of the fatigue cracks initiated during the test can not be treated rigorously. However, it is still thought to be practical and useful for the fatigue tests in long life range by the reason that the number of test specimens can be decreased dramatically in this testing method.