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首页> 外文期刊>Journal of Infrastructure Systems >Frequency Wave Number-Domain Analysis of Air-Coupled Impact-Echo Tests in Concrete Slab1
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Frequency Wave Number-Domain Analysis of Air-Coupled Impact-Echo Tests in Concrete Slab1

机译：混凝土板中空气耦合冲击回波试验的频率波数域分析1

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摘要

An air-coupled (also known as noncontact or contactless) sensing technique in the impact-echo method has been developed and its practical application to the field has been significantly improved. However, unlike the flexural mode frequency, the thickness mode frequency is difficult to measure using the air-coupled sensing technique mainly due to direct acoustic noise from the impact source. The direct acoustic noise is transmitted through the air, while the thickness mode is a portion of leaky Lamb waves from a platelike concrete slab, known as the zero-group velocity (ZGV) or standing wave motion. The noise components and leaky Lamb waves can be separated in the frequency-wave number (f-k) domain because of their different characteristics in phase velocity. In this paper, the f-k domain analysis is validated through both numerical simulations and experiments on two different thicknesses including full depth of concrete slab and shallow delamination. For shallow delamination, a dry-coupled ultrasonic transducer is applied to generate high-frequency ultrasonic waves corresponding to the ZGV frequency of the thickness while a microelectromechanical system (MEMS) is used as an air-coupled sensor. The results demonstrate that the proposed f-k domain analysis scheme and the applied hybrid hardware are capable of clearly detecting the thickness mode frequency and minimize the direct acoustic noise, while the conventional impact-echo method has limits.
机译：已经开发了冲击回波法中的空气耦合（也称为非接触式或非接触式）传感技术，并且其在现场的实际应用得到了显着改善。然而，与弯曲模式频率不同，主要由于来自冲击源的直接声噪声，使用空气耦合感测技术难以测量厚度模式频率。直接声噪声通过空气传播，而厚度模式是来自板状混凝土板的泄漏兰姆波的一部分，称为零群速度（ZGV）或驻波运动。噪声分量和泄漏的兰姆波可以在频率波数（f-k）域中分离，因为它们的相速度特性不同。本文通过数值模拟和实验对两种不同的厚度（包括混凝土板的全深度和浅层脱层）进行了数值模拟和实验验证，验证了f-k域分析的有效性。对于浅层分层，应用了干耦合超声换能器以生成与厚度的ZGV频率相对应的高频超声波，同时将微机电系统（MEMS）用作空气耦合传感器。结果表明，所提出的f-k域分析方案和所应用的混合硬件能够清晰地检测厚度模式频率，并将直接声噪声降至最低，而传统的冲击回波法则具有局限性。

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