Ultrasonic wavefield imaging (UWI) provides insightful spatial information about ultrasonic wave propagation in planar (2-D) space for nondestructive evaluation and structural health monitoring (NDE-SHM) applications. In all materials, the wavefronts of the incident and reflected waves propagate with unique patterns that may be represented by parametrized polar curves in 2-D geometric space. In this paper, a spatial ultrasonic wavefront characterization method based on a parametric curve laser scan is proposed to characterize the spatial ultrasonic wavefront for both isotropic and anisotropic materials. Three parametric curves (circular, hyperbolic, and cyclic-harmonic curves) were considered. Two wavefront characterization process were carried out, namely (i) deciding the parametric equation of the closed-form geometric plane curve via UWI, and (ii) measuring and updating the ultrasound via laser ultrasonic interrogation system (LUIS) and quantifying the values(s) of the predicted parametric curve equation using a temporal cross-correlation technique. The proposed method was tested on pristine aluminum and cross-ply CFRP plates to characterize the spatial incident and reflected wavefronts of the plates. The non-fiber direction region (105°⩽ϕS⩽165°) and the fiber direction region (165°⩽ϕS⩽195°) of the cross-ply CFRP plate were considered in the test. The laser circle scan and the laser cyclic-harmonic curve scan showed the ability to characterize the incident wavefronts of the S0 and A0 modes in the aluminum plate and the CFRP plate, respectively, followed by the laser hyperbolic curve scan. With the promising results obtained in the proposed method, the integration of the parametric curve scanning method into LUIS may provide a new approach to damage detection and useful information for ultrasonic algorithm design in NDE-SHM applications.

中文翻译：

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使用激光参数曲线扫描方法表征空间超声波波前

超声波场成像 (UWI) 为无损评估和结构健康监测 (NDE-SHM) 应用提供有关平面 (2-D) 空间中超声波传播的深入空间信息。在所有材料中，入射波和反射波的波前以独特的模式传播，这些模式可以由二维几何空间中的参数化极曲线表示。在本文中，提出了一种基于参数曲线激光扫描的空间超声波波前表征方法来表征各向同性和各向异性材料的空间超声波波前。考虑了三个参数曲线（圆形、双曲线和循环谐波曲线）。进行了两个波前表征过程，即（i）通过UWI确定闭合几何平面曲线的参数方程，(ii) 通过激光超声询问系统 (LUIS) 测量和更新超声，并使用时间互相关技术量化预测参数曲线方程的值。所提出的方法在原始铝和交叉层 CFRP 板上进行了测试，以表征板的空间入射和反射波前。试验中考虑了交叉层CFRP板的非纤维方向区域（105°⩽φS⩽165°）和纤维方向区域（165°⩽φS⩽195°）。激光圆扫描和激光循环谐波曲线扫描显示了分别表征铝板和 CFRP 板中 S0 和 A0 模式入射波前的能力，然后是激光双曲线扫描。在所提出的方法中获得了有希望的结果，