Capineri Lorenzo, Taddei Lorenzo, Marino Merlo Eugenio
Department of Information Engineering, University of Florence, Via S. Marta 3, 50139 Firenze, Italy.
Sensors (Basel). 2024 Mar 17;24(6):1926. doi: 10.3390/s24061926.
The early detection of small cracks in large metal structures is a crucial requirement for the implementation of a structural health monitoring (SHM) system with a low transducers density. This work tackles the challenging problem of the early detection of submillimeter notch-type defects with a semielliptical shape and a groove at a constant width of 100 µm and 3 mm depth in a 4.1 mm thick aluminum plate. This defect is investigated with an ultrasonic guided wave (UGW) A mode at 550 kHz to investigate the long range in thick metal plates. The mode selection is obtained by interdigital transducers (IDTs) designed to operate with a 5 mm central wavelength. The novel contribution is the validation of the detection by pulse-echo and pitch and catch with UGW transducers to cover a distance up to 70 cm to reduce the transducers density. The analysis of scattering from this submillimeter defect at different orientations is carried out using simulations with a Finite Element Model (FEM). The detection of the defect is obtained by comparing the scattered signals from the defect with baseline signals of the pristine laminate. Finally, the paper shows that the simulated results are in good agreement with the experimental ones, demonstrating the possible implementation in an SHM system based on the efficient propagation of an antisymmetric mode by IDTs.
在低密度传感器的结构健康监测（SHM）系统中，早期检测大型金属结构中的小裂纹至关重要。这项工作解决了在4.1毫米厚铝板中早期检测亚毫米级半椭圆形缺口型缺陷以及宽度恒定为100微米、深度为3毫米的凹槽这一具有挑战性的问题。采用550千赫兹的超声导波（UGW）A模式对该缺陷进行研究，以探究厚金属板中的远距离情况。模式选择通过设计用于以5毫米中心波长运行的叉指换能器（IDT）实现。新颖之处在于通过UGW换能器的脉冲回波以及间距和捕捉方式对检测进行验证，以覆盖长达70厘米 的距离，从而降低传感器密度。使用有限元模型（FEM）模拟对该亚毫米缺陷在不同方向上的散射进行分析。通过将缺陷的散射信号与原始层压板的基线信号进行比较来实现缺陷检测。最后，本文表明模拟结果与实验结果吻合良好，证明了基于IDT的反对称模式有效传播在SHM系统中的可能实现。
