中文摘要：

使用超声导波进行无损检测是实现结构健康监测的重要手段，但是其多模态特性会增加损伤信号提取难度，因此需要在激发时尽可能激励单一模态。使用粘贴于结构表面的压电晶片激发和接收超声导波，通过多种尺寸晶片在不同结构厚度下的导波试验，对导波各模态的激发特性进行了研究。结果表明附着于结构表面的压电晶片不但可激发S0模态，同时也可激发出氏模态；为了有效抑制A0模态的幅值，激发晶片的直径需要大于A0模态的波长。

英文摘要：

Guided waves are used in structure health monitoring. However, the signal will be too complicated to distinguish the damage as multi-modes propagating in the wave-guide. Single mode only is therefore needed in actuating the guided waves. The surface bonded piezoelectric wafers are used as actuator and sensor in this paper. Based on the experiments, the excitabilities of different modes are studied. The results show that not only the So mode, but also the A0 mode will be stimulated by the surface bonded wafer. In order to inhibit the A0 mode, the diameter of the wafer should be lager than the wavelength of the mode.