In pipe inspection using ultrasonic guided wave technique, the current commercial transmitters are designed for the unidirectional guided wave excitation using multiple circular piezoelectric transducers arrays in the axial direction. However, the source with many individual transducer elements in arrays has difficulty in achieving an axisymmetric loading perfectly for defect detection. Therefore, a quasi-axisymmetric wave is formed due to many undesired wave modes are launched instead of a pure axisymmetric wave at a given excitation frequency. In this paper, a realistic superposition model of axial multiple transducer arrays is proposed. The model has many potential applications; one example is investigating the source influence on the generated quasi-axisymmetric wave effect. The analytical model is employed to achieve the predictions for investigating a transmitter’s influence for the unidirectional enhancement of torsional T(0,1) guided wave mode excitation in a pipe inspection system composing of three piezoelectric transducer ring arrays. The excitation function with variable power levels among transducers in arrays is also introduced. The predictive results using the analytical model for the distribution of circumferential displacement amplitudes over time are verified using the finite element method and a CLV-3D laser vibrometry measurement on a 219.1-mm-outer-diameter steel pipe without defect. A comparison between calculated and test results has been analysed quantitatively. The respective results are in good agreement. Thus, predictions for the superposed wavefield can be used to analyse the realistic characterisation of the excitation function in axial multiple transducer arrays. Additionally, a sensitivity analysis for part-circumferential crack detection using the quasi-axisymmetric torsional modes generated is also evaluated using finite element modelling.

在使用超声波导波技术的管道检测中，当前的商用发射机设计用于使用轴向多个圆形压电换能器阵列的单向导波激励。然而，在阵列中具有许多单独换能器元件的源很难实现完美的轴对称负载以进行缺陷检测。因此，由于在给定的激励频率下发射了许多不需要的波模式而不是纯轴对称波，因此形成了准轴对称波。在本文中，提出了轴向多换能器阵列的真实叠加模型。该模型有许多潜在的应用；一个例子是研究震源对产生的准轴对称波效应的影响。该分析模型用于实现预测，用于研究发射机对由三个压电换能器环形阵列组成的管道检测系统中扭转 T(0,1) 导波模式激励单向增强的影响。还介绍了阵列换能器之间具有可变功率电平的激励函数。使用有限元方法和 CLV-3D 激光测振仪测量外径为 219.1 毫米的无缺陷钢管，验证了使用分析模型的圆周位移幅度随时间分布的预测结果。已对计算结果和测试结果之间的比较进行了定量分析。各自的结果非常吻合。因此，叠加波场的预测可用于分析轴向多换能器阵列中激励函数的实际特征。此外，还使用有限元建模评估了使用生成的准轴对称扭转模式进行的部分周向裂纹检测的灵敏度分析。