焊接薄板中S0兰姆波对槽型缺陷响应特性的数值研究*

采用数值仿真方法,就焊接薄板中S_0兰姆波对槽型缺陷的响应特性以及焊缝对S_0兰姆波槽型缺陷检测灵敏度的影响开展了数值研究。数值仿真结果表明,S_0_R信号(经槽型缺陷反射的S_0兰姆波回波信号)的反射比率随槽型缺陷深度的增大而单调增加;S_0_R信号的反射比率随槽型缺陷宽度的变化呈非单调变化关系,可将S_0_R信号的反射比率及其持续时间一并加以考虑,以评价槽型缺陷宽度的变化。随着焊缝余高的增加,S_0兰姆波对槽型缺陷的检测灵敏度将降低;随着焊缝宽度的增加,S_0兰姆波对槽型缺陷检测灵敏度的影响并不明显;相比之下,焊缝余高是影响S_0兰姆波槽型缺陷检测灵敏度的主要因素。研究结果表明,将S_0兰姆波用于检测隐藏于焊缝背后的槽型缺陷,是具有可行性的。所得结果对于发展焊接薄板的超声兰姆波无损检测技术,具有一定的理论指导意义和实际参考价值。

Numerical study on response characteristics of S0 Lamb waves to groove defects in welded thin plates

The response characteristics of the S₀ Lamb wave propagation to the groove defects, as well as the influences of the weld joint on the detection sensitivity of the S₀ Lamb wave to the groove defects, have been investigated using numerical simulations. The simulation results show that the reflection ratio of the S_{0_R} signal (i.e. the echo signal of the S₀ Lamb wave reflected by the groove defect) monotonously increases with increase in the depth of the groove defects. However, the change trend of the reflection ratio of the S_{0_R} signal is no longer monotonic with change in the width of the groove defects. It is proposed that the width of the groove defects can be evaluated via simultaneously considering both the reflected ratio of the S_{0_R} signal and its duration. It is found that the detection sensitivity of the S₀ Lamb wave to the groove defects decreases with increase in the weld reinforcements. In contrast, the detection sensitivity of the S₀ Lamb wave to the groove defects is