兰姆波在搭接焊缝上的干涉

Interference of Lamb Waves at Overlap Joints

采用数值模拟和理论方法研究兰姆波在激光搭接焊缝上的干涉。数值模拟激励频率500 k Hz的兰姆波S_0和A_0模态,在2 mm厚不锈钢板的搭接焊缝模型上的干涉现象。研究发现兰姆波在搭接焊缝前边沿的反射回波和后边沿的反射回波相互叠加,造成兰姆波在不同宽度的搭接焊缝上的反射率呈周期性地变化;且不同频率的兰姆波在相同宽度的搭接焊缝上有不同程度的干涉。通过仿真结果得到:当两个反射回波的相位差为半波长的奇数倍时,形成相减干涉;当两个波的相位差为偶数倍时,形成增长干涉。

The interference phenomenon of Lamb waves at overlap joints are researched by the numerical simulation and theoretical method. The numerical method is used to simulate the interference occurred when the Lamb waves S0 and A0 mode （at an exciting frequency of 500 kHz） propagate through welds on a 2 mm-thick stainless steel plate. It is found that the waves reflected from the end edge will interfere with the waves reflected from the front edge. The interference was lead to the reflection coefficients change with the weld width periodically. In addition, Lamb waves with different frequency have different interference on the same overlap joint. The interference is observed by simulation. The Lamb waves occur increase interference when the phase difference between two waves is odd times of half wavelength. Moreover, the Lamb waves occur destructive interference when the phase difference between two waves is even times of half wavelength.