基于水平剪切导波的钢桥面板疲劳裂纹在线识别方法

SH Guided Wave-based Inspection Method for Crack Localization in Orthotropic Steel Bridge Decks

正交异性钢桥面板广泛应用于大跨度桥梁,然而该类桥面板极易疲劳损伤并出现开裂,严重影响桥梁的服役安全.传统逐点扫描的无损检测方法无法满足大跨度桥梁全域快速的检测要求,迫切需要发展在线智能监测方法.与频散的Lamb波相比,零阶水平剪切波(SH_(0)波)因其非频散特性,是实现正交异性钢桥面板在线监测的理想导波模态,但相关研究极为匮乏.论文首先通过有限元模拟系统研究了SH_(0)波与U肋焊缝的作用规律,发现在一阶截止频率以下,U肋和焊缝对SH_(0)波在顶板中的传播影响较小,可忽略不计.在一阶截止频率以上,U肋会导致SH_(0)波部分能量转化为SH_(1)波,但产生的SH_(1)波幅值较小.接着通过自主研制的压电换能器,实现了16mm厚顶板中单模态SH_(0)波的激励与接收.在此基础上,实验验证了SH_(0)波与U肋及焊缝的作用规律.最后,搭建了SH_(0)波焊缝裂纹检测系统,实验证明了SH_(0)波可以准确识别正交异性钢桥面板中焊缝典型裂纹缺陷.论文的工作可为发展基于超声导波的正交异性钢桥面板的智能监测技术奠定相关基础.

The orthotropic steel bridge deck(OSBD)is widely used in long-span bridges.However,fatigue cracks easily occur in OSBDs,which seriously affects the safety of bridges.Usually,the conventional nondestructive testing methods only cover the local region below the transducer,so there is an urgent need for the development of structural health monitoring(SHM)technologies capable of scanning a large area from a single position on the bridge deck.Compared with the dispersive Lamb waves,the fundamental shear horizontal wave(SH_(0)wave)is an ideal wave mode in developing SHM systems for OSBDs due to its non-dispersive characteristics,but the related research is extremely scarce.This paper first studies the interaction between an SH_(0)wave and a U-shaped stiffener with a weld by finite element simulations.It is found that below the first cutoff frequency of SH guided wave,the U-shaped stiffener and weld have little influence on the propagation of the SH_(0)wave in the deck plate and can be neglected.Above the first cutoff frequency,apart of the SH_(0)wave will be converted into the SH_(1)wave(the first-order SH mode)when encountering the U-shaped stiffener,but the amplitude of the generated SH_(1)wave is quite small.Then,piezoelectric transducers are developed for excitation and reception of the single-mode SH_(0)wave in a 16-mm-thick deck plate.The developed transducer for generating the SH_(0)wave is a thicknessshear piezoelectric device,while the sensor for receiving the SH_(0)wave is a face-shear piezoelectric transducer.After that,experiments are conducted to verify the simulated results for the case of an SH_(0)wave encountering a U-shaped stiffener.The obtained experimental results accord well with the simulated ones.Finally,an SH_(0)wave-based inspection system is developed to detect cracks in OSBDs.Results show that the cracks in OSBDs can be accurately identified by the SH_(0)wave.This work can lay a foundation for developing guided wave-based intelligent monitoring technologies for OSBDs.