Wilcox Paul D
Department of Mechanical Engineering, University of Bristol, Bristol, BS8 1TR, UK.
IEEE Trans Ultrason Ferroelectr Freq Control. 2003 Jun;50(6):699-709. doi: 10.1109/tuffc.2003.1209557.
Omni-directional guided wave array transducers contain a circular pattern of elements that individually behave as omni-directional point transmitters or receivers. The data set acquired from such an array contains time-domain signals from each permutation of transmitter and receiver. A phased addition algorithm is developed that allows an omni-directional, B-scan image of the surrounding plate to be synthesized from any geometry of array. Numerically simulated data from a single reflector is used to test the performance of the algorithm. The results from an array containing a fully populated circular area of elements (Type I array) are found to be good, but those from an array containing a single ring of elements (Type II array) contain many large side-lobes. An enhancement to the basic-phased addition algorithm is presented that uses deconvolution to suppress these side-lobes. The deconvolution algorithm enables a Type II array to equal the performance of a Type I array of the same overall diameter. The effect of diameter on angular resolution is investigated. Experimental data obtained from a guided wave array containing electromagnetic acoustic transducers (EMAT) elements for exciting and detecting the So Lamb wave mode in a 5-mm thick aluminium plate are processed with both algorithms and the results are discussed.
全向导波阵列换能器包含呈圆形排列的元件，这些元件各自的表现如同全向点发射器或接收器。从这样一个阵列获取的数据集包含来自发射器和接收器每种排列组合的时域信号。开发了一种相加法算法，该算法能根据阵列的任何几何形状合成周围板材的全向B扫描图像。利用来自单个反射器的数值模拟数据来测试该算法的性能。发现包含元件完全填充圆形区域的阵列（I型阵列）的结果良好，但包含单个元件环的阵列（II型阵列）的结果包含许多大的旁瓣。提出了对基本相加法算法的一种改进，该改进使用去卷积来抑制这些旁瓣。去卷积算法使II型阵列能够达到相同总直径的I型阵列的性能。研究了直径对角分辨率的影响。用这两种算法处理了从一个包含电磁超声换能器（EMAT）元件的导波阵列获得的实验数据，这些元件用于在5毫米厚的铝板中激发和检测So兰姆波模式，并对结果进行了讨论。
