Fatigue Failure of Large-Diameter Cast Iron Mains
Fatigue Failure of Large-Diameter Cast Iron Mains
复制标题
大直径铸铁主管的疲劳失效
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
Y. Kleiner
中科院分区：
文献类型：
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作者：
B. Rajani;Y. Kleiner
自来水公司工程师报告了大直径总水管在没有警告的情况下突然发生故障的情况，没有先前泄漏的迹象，也没有断裂表面腐蚀的视觉证据。通常，这些发生故障的电源已经运行了 80 多年，没有出现重大问题。一种可能的解释可归因于交替或波动的应力，例如由交通繁忙和周期性运行水压以及偶尔发生的瞬变引起的应力。如果管道撞击具有尖锐几何形状和高刚度的物体（例如岩石或石头），这些波动应力会加剧。铸铁的疲劳已在铸铁桥梁、柱、发动机组等结构元件的背景下进行了广泛的研究，但并未在埋地灰口铸铁水管的背景下进行了广泛的研究。多年来开发的疲劳分析方法涉及大量经验主义，并将工程原理与实验观察相结合。因此，可以公平地说，疲劳分析结果应该更多地作为指导，而不是作为精确或准确的答案。此前尚未探索过解释埋地铸铁管疲劳失效的机械方法。本文探讨了断裂力学方法 (LEFM) 的应用来解释铸铁管中因疲劳机制而发生的一些失效。它致力于深入了解灰口铸铁管在受到由于表面交通负载、工作压力变化和瞬态压力发生而引起的交变（通常也称为重复或可变）应力时发生疲劳失效的可能性。值得注意的是，所提出的分析涉及灰口铸铁管类型，其碳呈片状石墨形式，是北美和欧洲现有铁干线的主要材料。
Water utility engineers have reported on large diameter water main failures that occurred suddenly without warning, no signs of prior leaks and no visual evidence of corrosion on the fracture surfaces. Often these failed mains had been operating without major problems for over 80 years. A possible explanation may be attributed to alternating or fluctuating stresses such as those caused by heavy traffic and cyclical operating water pressure with occasional occurrences of transients. These fluctuating stresses are accentuated if the pipe impinges on an object with sharp geometry and high stiffness like a rock or a stone. Fatigue of cast iron has been extensively studied in the context of cast iron bridges, structural elements such as columns, engine blocks, etc, but not in the context of buried, grey cast iron water pipes. Fatigue analysis methods developed over the years involve a lot of empiricism and combine engineering principles with experimental observations. Consequently, it is fair to say that fatigue analysis results should be taken more as a guide than as precise or accurate answers. A mechanistic approach to explain fatigue failures of buried cast iron pipes had not been previously explored. This paper explores the application of the fracture mechanics approach (LEFM) to explain some failures in cast iron pipes that occur through the fatigue mechanism. It endeavors to provide insight into the plausibility of fatigue failures in grey cast iron pipes when and if subjected to alternating (also often referred to as repeated or variable) stresses due to surface traffic loads, operating pressure variations and transient pressure occurrences. It is important to note that the proposed analysis refers to grey cast iron pipe type, with carbon in form of flake graphite, which is the predominant material of existing iron trunk mains in North America and Europe.