Hayashi Takahiro, Kawashima Koichiro, Sun Zongqi, Rose Joseph L
Department of Mechanical Engineering, Nagoya Institute of Technology, Gokiso Showa Nagoya 466-8555, Japan.
J Acoust Soc Am. 2003 Mar;113(3):1241-8. doi: 10.1121/1.1543931.
Focusing is one of the most promising techniques for the detection of small defects in pipe works, in which guided waves including longitudinal and flexural modes are tuned so that ultrasonic energy can be focused at a target point in a pipe, and analysis of reflected waves gives information on defects such as location and size. In this paper, the focusing technique is discussed by way of a simulation of guided wave propagation in pipe by a semianalytical finite element method (SAFE). Experiments and SAFE calculations were compared for waveforms transmitted by a single transducer and received at different circumferential positions initially, and then the focusing phenomena were experimentally observed using focusing parameters obtained by calculations. Calculation and visualization were conducted to clarify focusing phenomena in pipe in investigating the potential of the focusing technique. These results show that the time-reversal idea helps in understanding focusing and that resolution of focusing is strongly affected by incident waveforms as well as the number of channels available in an experiment.
聚焦是检测管道工程中小缺陷最具前景的技术之一，在该技术中，包括纵向和弯曲模式的导波被调谐，以便超声能量能够聚焦在管道中的目标点上，并且对反射波的分析可以提供有关缺陷位置和尺寸等信息。本文通过半解析有限元法（SAFE）对管道中导波传播进行模拟来讨论聚焦技术。最初比较了由单个换能器发射并在不同圆周位置接收的波形的实验和SAFE计算结果，然后使用通过计算获得的聚焦参数对聚焦现象进行了实验观察。为了在研究聚焦技术的潜力时阐明管道中的聚焦现象，进行了计算和可视化。这些结果表明，时间反转概念有助于理解聚焦，并且聚焦分辨率受到入射波形以及实验中可用通道数量的强烈影响。
