薄壁管道内壁缺陷的周向导波检测

Nondestructive testing of the interior radial crack of thin-walled pipe by circumferential guided waves

采用半解析有限元法计算圆环周向导波频散特性,群速度的计算可以不依赖于相速度。以外径202 mm,内径200 mm的铝环为例,计算了其在2.5 MHz频率时最低阶模态的相速度、群速度和振型。进一步设计了实验方案,对选定模态导波分别经过无裂纹和径向深0.5 mm的内壁裂纹的铝环的回波波形进行了分析,通过回波的时间与声程计算群速度进而确定模态。结果表明,裂纹缺陷处会发生模式转换,通过反射回波可以较精确的定位铝环内壁的单一缺陷。

The Semi-Analytical Finite Element approach is used for calculating dispersion curves of an annulus in the circumferential direction. As a result, the group velocities can be calculated independent of phase velocities. Phase velocities, group velocities and displacement fields of the lowest order mode of the circular aluminum annulus （Outer diameter： 202 mm, inner diameter： 200 mm） are calculated at the frequency of 2.5 MHz. In experiments, the received waveform of thin-walled aluminum annuluses with and without the interior crack （Depth： 0.5 mm） is analyzed, then the group velocity is calculated by the time and distance of the backscattered signal in order to determine the mode. Mode conversion by the crack is detected and the interior crack in the aluminum annulus is located accurately by experimental data.