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Study on Evaluation Method for Safety Margin of Degraded Piping Against Seismic Loading with Multi-Fracture Mode

多断裂模式退化管道抗震安全裕度评估方法研究

基本信息

批准号：
16360049
负责人：
SHIRATORI Masaki
金额：
$ 9.79万
依托单位：
Yokohama National University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

项目摘要

The piping system is one of the major equipment in the nuclear power plant. Because it is assumed that fracture of the piping cause serious damage to whole system of the nuclear power plant, sufficient safety must be ensured against the defect and caused degradation of the piping. In addition, large margin of seismic safety has been taken in Japan because of a lot of earthquakes. However, effect of aged piping on seismic safety has not been clarified.The aged piping of a nuclear power plants has possibility to have some defects such as SCC (Stress Corrosion Cracking) cracks and local thinning. In order to evaluate tolerance limit of the degraded piping, a series of large scale four-point bending tests on straight pipe and shaking table tests using 3-D piping system models, low cycle fatigue tests for the degraded pipes were carried out as a part of the "Aged Piping Committee" project sponsored by National Research Institute for Earth Science and Disaster Prevention. And local thinning bent pipes bending tests were done in National Research Institute for Earth Science and Disaster Prevention in 2002.The purpose of this study in this paper is to establish analytical approaches by which the low cycle fatigue strength and failure behavior of degraded piping can be simulated against seismic loading with multi-fracture mode. A series of finite element analyses, dynamic analysis and static analysis, have been performed. A series of elasto-plastic analyses have been carried out for the locally thin-walled straight piping loaded cyclic four-point bending and locally thin-walled elbow piping loaded cyclic in-plane or out-of-plane bending and then 3D piping system loaded dynamic loading. It has been found that the ratcheting or ovaling behavior observed in the experiment can be simulated well by finite element analysis.

管道系统是核电站的主要设备之一。由于假定管道的断裂会对核电厂的整个系统造成严重的破坏，因此必须保证足够的安全性，以防止管道的缺陷和退化。此外，由于地震频繁，日本采取了很大的地震安全余量。然而，老化管道对地震安全的影响尚未明确。核电站老化管道有可能出现应力腐蚀开裂、局部变薄等缺陷。为了评估退化管道的容差极限，在国家地球科学与防灾研究院“老化管道委员会”项目中，利用三维管道系统模型进行了一系列大型直管四点弯曲试验和振动台试验，并对退化管道进行了低周疲劳试验。并于2002年在国家地球科学与防灾研究所进行了局部变薄弯管弯曲试验。本文的研究目的是建立退化管道在多断裂模式地震荷载下低周疲劳强度和破坏行为的模拟分析方法。进行了一系列的有限元分析，动力分析和静力分析。对局部薄壁直管加载循环四点弯曲、局部薄壁弯头管加载面内或面外循环弯曲以及三维管道系统加载动载荷进行了弹塑性分析。实验中观察到的棘轮或卵形行为可以用有限元分析很好地模拟。