Abstract Tubular structures are widely used in infrastructure, especially for pipes and marine installations. Corrosion is a key damage type for these structures, and if undetected may cause structural deficiency or even collapse. This paper investigates the effects of localised corrosion on the vibration properties of axisymmetric tubular structures and proposes a baseline-free damage identification method to overcome the fact that the difference between undamaged and damaged properties is usually small and contaminated by noise. The proposed vibration-based method exploits the phenomenon of repeated mode pairs which is peculiar to axisymmetric tubular structures with non-axisymmetric damage. Unlike intact tubular structures, it is found that each vibration mode of a locally damaged tubular structure comprises of two components: active and passive. The active component is sensitive to the local damage and can be used to infer damage existence while the passive component is retentive of the undamaged pipe's properties. Therefore, the passive component of a damaged pipe ’ s local vibration mode pair (LVMP) can be used to predict its baseline (undamaged) modal properties, which in this research was achieved within a margin of ±2%, whereas the active component confirms damage existence. The work also establishes the criteria for validation of LVMPs through experimental tests involving various corrosion scenarios ranging from longitudinal strips to through-thickness pits. Based on the obtained results, it is proposed that the properties of LVMPs can be linked to corrosion-like local damage in axisymmetric tubular structures, underpinning a new damage detection and identification approach.

中文翻译：

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用于轴对称管状结构损伤识别的局部振动模式对

摘要 管状结构广泛应用于基础设施，特别是管道和海洋设施。腐蚀是这些结构的关键损坏类型，如果未被发现，可能会导致结构缺陷甚至倒塌。本文研究了局部腐蚀对轴对称管结构振动特性的影响，并提出了一种无基线损伤识别方法，以克服未损伤和损伤特性之间的差异通常很小且受噪声污染的事实。所提出的基于振动的方法利用了具有非轴对称损伤的轴对称管状结构所特有的重复模式对现象。与完整的管状结构不同，发现局部损坏的管状结构的每种振动模式包括两个分量：主动和被动。主动分量对局部损坏很敏感，可用于推断损坏的存在，而被动分量保持未损坏管道的特性。因此，损坏管道的局部振动模态对 (LVMP) 的被动分量可用于预测其基线（未损坏）模态特性，在本研究中实现了 ±2% 的裕度，而主动分量证实损害存在。该工作还通过涉及从纵向条带到贯穿厚度坑的各种腐蚀场景的实验测试建立了验证 LVMP 的标准。基于获得的结果，提出 LVMP 的特性可以与轴对称管状结构中的类腐蚀局部损伤相关联，