混凝土分层缺陷的超声检测方法研究

为解决混凝土结构中分层缺陷的在线非接触检测难题,论文提出了利用空气耦合(简称:空耦)超声导波定量检测混凝土结构中分层缺陷的新方法。首先研究了空耦超声导波在混凝土结构中的传播特性,理论分析和实验表明,利用空耦超声波以入射角8.7°入射厚度为50 mm的混凝土板时,可以激发以A0模态为主的导波。然后构建了空耦超声导波扫查实验系统,在混凝土结构单侧利用一对倾斜8.7°的空耦探头激励和接收导波信号,通过分析发现A0模态对分层缺陷敏感,且其幅度与扫查路径中的分层缺陷尺寸存在单调变化关系;在此基础上,对检测区域进行扫查,利用不同位置处的导波信号幅度实现分层缺陷的二维成像。实验结果表明,该方法不仅可以避免耦合剂对检测结果的影响,同时可实现对服役状态下混凝土结构中分层位置及尺寸的定量检测。

Ultrasonic detection method for concrete delamination defects

To solve the difficult problem of online nondestructive detection of delamination defects in concrete structures, a new method using air-coupled ultrasonic guided waves is proposed in this paper. Firstly the propagation characteristics of air-coupled ultrasonic guided waves in concrete structures are studied. Theoretical analysis and experiments show that a single A₀ mode can be excited when an air-coupled ultrasonic wave is incident on the concrete slab of 50 mm thick at 8.7°. Then, an experimental system of automatic scan test using air-coupled ultrasonic guided wave is constructed, and a pair of air-coupled probes tilted at an angle of 8.7° is used to excite and receive the guided wave signals on one side of the concrete structure, and it is found that the A₀ mode guided wave is sensitive to the delamination defects, and there is a monotonic change relationship between its amplitude and the size of the delamination defects in the scanning path. Based on this, the detection area is scanned, and two-dimensional imaging of the delamination defects is realized by the guide wave signal amplitudes at different positions. The experimental results show that this method can not only avoid the influence of coupling agent on the detection results, but also achieve the quantitative detection of the location and size of delamination in laminated concrete structures under service condition.