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).

这项研究的目的是开发一种基于责任的方法来剩余生活评估。该方法利用了通过极端和图像处理统计估计的最大裂纹长度。 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恒定间隔的极端应变周期和与测量值的比较，以及开发基于可靠性的生命评估的方法。主要结果总结如下。首先，图像处理成功地应用于大量短疲劳裂纹的尺寸测量，用于应用极端的统计数据。测量中消耗的时间和精力可以大大减少。在<plus-minus> 10秒的相对误差中，可以测量大于30 gm的裂纹长度，发现估计蠕变效率的最大裂纹长度的限制。也就是说，发现在裂纹结合发生之前，估计的最大裂纹长度与测量值一致，而在结合发生后，前者偏离了后者。这对于基于最大裂纹长度的生命评估很重要。在本文中，提出了“修改后的返回期”的新概念，并使用此概念开发了一种基于可靠性的生命评估方法。此方法使能够预测与低故障概率（或高可靠性）相对应的剩余寿命。