School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2011 Jul;58(7):1430-41. doi: 10.1109/TUFFC.2011.1962.
A frequency-steerable acoustic transducer (FSAT) is employed for imaging of damage in plates through guided wave inspection. The FSAT is a shaped array with a spatial distribution that defines a spiral in wavenumber space. Its resulting frequency-dependent directional properties allow beam steering to be performed by a single two-channel device, which can be used for the imaging of a two-dimensional half-plane. Ad hoc signal processing algorithms are developed and applied to the localization of acoustic sources and scatterers when FSAT arrays are used as part of pitch-catch and pulse-echo configurations. Localization schemes rely on the spectrogram analysis of received signals upon dispersion compensation through frequency warping and the application of the frequency-angle map characteristic of FSAT. The effectiveness of FSAT designs and associated imaging schemes are demonstrated through numerical simulations and experiments. Preliminary experimental validation is performed by forming a discrete array through the points of the measurement grid of a scanning laser Doppler vibrometer. The presented results demonstrate the frequency-dependent directionality of the spiral FSAT and suggest its application for frequency-selective acoustic sensors, for the localization of broadband acoustic events, or for the directional generation of Lamb waves for active interrogation of structural health.
频率可控声换能器（FSAT）用于通过导波检测对板中的损伤进行成像。FSAT 是一种具有空间分布的形状阵列，该空间分布定义了波数空间中的螺旋线。其产生的频率相关的指向性特性允许通过单个双通道设备进行波束转向，该设备可用于二维半平面的成像。特别开发了信号处理算法，并将其应用于使用 FSAT 阵列作为纵波和脉冲回波配置的一部分时声源和散射体的定位。定位方案依赖于接收信号的声谱图分析，该分析通过频率翘曲进行色散补偿，并应用 FSAT 的频率-角度图特性。通过数值模拟和实验验证了 FSAT 设计和相关成像方案的有效性。通过形成通过扫描激光多普勒测振仪的测量网格点的离散阵列来进行初步的实验验证。所提出的结果表明了螺旋 FSAT 的频率相关指向性，并表明其可用于频率选择声传感器，用于宽带声事件的定位，或用于兰姆波的定向产生，以主动询问结构健康状况。
