识别薄板中兰姆波和体波的阶梯板方法

斜探头在某些频率下激励出的兰姆波,其群速度与体波的传播速度相近,所以通过判断传播速度不易区分出兰姆波和体波。通过数值模拟和实验,分别研究了激励频率为2 MHz的纵波和S0模态兰姆波在阶梯板上的反射特性,发现:在阶梯板上入射S0模态兰姆波时,有反射回波;而入射纵波时,无反射回波。基于这种反射特性的差别,提出了一种利用阶梯板区别薄板中兰姆波和体波的方法,该方法可用于确认探头的激励特性。

A method of using step plates to distinguish Lamb waves from bulk waves in thin plates

Lamb wave in thin plate is generally excited by using an angle beam transducer. At some frequencies, the group velocity of Lamb wave excited by an angle beam transducer is nearly same as the velocity of bulk wave, so it is not easy to distinguish Lamb wave from bulk wave through the propagation velocity. This paper respectively researches the reflection characteristics of both the Lamb wave S0 mode and the longitudinal wave in step plates by finite element method (FEM) and experiments, when the incident frequency is 2 MHz. Moreover, it has been found that Lamb waves S0 mode are reflected from the step plates and that bulk waves are not. Based on this reflection characteristic, a method of using step plates to distinguish Lamb waves from bulk waves is presented.