Development of A Reliability-based Method for Remaining Life Evaluation Using Extremes Statistics Analysis of Short Fatigue Cracks

利用短疲劳裂纹的极值统计分析开发基于可靠性的剩余寿命评估方法

基本信息

批准号：
62460078
负责人：
ICHIKAWA Masahiro
金额：
$ 4.61万
依托单位：
The University of Electro-Communications
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1989
项目状态：
已结题

项目摘要

This research was conducted aiming at development of a liability-based method for remaining life evaluation. The method makes use of the maximum crack length estimated by means of statistics of extremes and image processing. The research involves construction of a high temperature fatigue testing system (mainly, a control system using a microcomputer and a strain measurement system), execution of creep-fatigue tests of the austenitic stainless steel SUS316L at 650 ﾟC in air, introduction of image processing technique including development of some new algorithms, size measurement of a large number of short fatigue cracks, estimation of the maximum crack length based on statistics of extremes at a constant interval of strain cycles and comparison with the measured value, and development of a reliability-based method for remaining life evaluation. The principal results are summarized as follows.First, image processing was successfully applied to size measurement of a large number of short fatigue cracks to which statistics of extremes was applied. The time and efforts consumed in measurement could be greatly reduced. It was possible to measure the crack length larger than 30 gm within the relative error of <plus-minus>10Second, a limitation of estimating the maximum crack length in creep-fatigue was found. That is, it was found that up to occurrence of crack coalescence, the estimated maximum crack length was in agreement with the measured one, whereas after occurrence of coalescence the former deviated from the latter. This is important in remaining life evaluation based on the maximum crack length.Finally, the new concept of "modified return period" was proposed , and a reliability-based method for remaining life evaluation was developed using this concept. This method enables to predict the remaining life corresponding to a low failure probability (or high reliability).

本研究旨在开发一种基于责任的剩余寿命评估方法，该方法利用通过极值统计和图像处理估计的最大裂纹长度。主要是使用微电脑的控制系统和应变测量系统），在空气中进行奥氏体不锈钢SUS316L在650℃的蠕变疲劳试验，引入图像处理技术，包括开发一些新算法，大量短疲劳裂纹的尺寸测量，基于恒定应变周期间隔的极值统计并与测量值进行比较来估计最大裂纹长度，以及开发基于可靠性的剩余寿命评估方法。结果总结如下：首先，图像处理成功地应用于大量短疲劳裂纹的尺寸测量，应用极值统计可以大大减少测量所消耗的时间和精力。裂纹长度在相对范围内大于30gm误差<正负>10 其次，发现了蠕变疲劳中最大裂纹长度估计的局限性，即发现直到裂纹合并发生，估计的最大裂纹长度与测量的一致。，而在发生合并后，前者与后者发生偏差，这对于基于最大裂纹长度的剩余寿命评估具有重要意义。最后，提出了“修正重现期”的新概念，并提出了一种基于可靠性的剩余寿命方法。评估是利用这一概念开发的。该方法能够预测与低故障概率（或高可靠性）相对应的剩余寿命。