Huthwaite Peter, Seher Matthias
IEEE Trans Ultrason Ferroelectr Freq Control. 2015 May;62(5):927-38. doi: 10.1109/TUFFC.2014.006884.
Pipe wall loss caused by corrosion can be quantified across an area by transmitting guided Lamb waves through the region and measuring the resulting signals. Typically the dispersive relationship for these waves, which means that wave velocity is a known function of thickness, is exploited, enabling the wall thickness to be determined from a velocity reconstruction. The accuracy and quality of this reconstruction is commonly limited by the angle of view available from the transducer arrays. These arrays are often attached as a pair of ring arrays on either side of the inspected region, and due to the cylindrical nature of the pipe, waves are able to travel in an infinite number of helical paths between any two transducers. The first arrivals can be separated relatively easily by time gating, but by using just these components the angle of view is severely restricted. To improve the viewing angle, it is necessary to separate the wavepackets. This paper provides an outline of a separation approach: initially the waves are backpropagated to their source to align the different signals, then a filtering technique is applied to select the desired components. The technique is applied to experimental data and demonstrated to robustly separate the signals.
由腐蚀引起的管壁损失可以通过在一个区域内传输导波兰姆波并测量产生的信号来进行量化。通常利用这些波的色散关系，即波速是厚度的已知函数，从而能够从速度重建中确定壁厚。这种重建的准确性和质量通常受到换能器阵列可用视角的限制。这些阵列通常作为一对环形阵列连接在被检查区域的两侧，并且由于管道的圆柱形性质，波能够在任意两个换能器之间以无限数量的螺旋路径传播。首次到达的信号可以通过时间选通相对容易地分离出来，但仅使用这些分量时，视角会受到严重限制。为了改善视角，有必要分离波包。本文概述了一种分离方法：首先将波反向传播到其源以对齐不同的信号，然后应用滤波技术来选择所需的分量。该技术应用于实验数据，并证明能够稳健地分离信号。
