锯齿形超声相控阵声场特性
Acoustic field characteristics of serrated ultrasonic phased array transducers

针对空心轴类零件的外表面纵向裂纹，该文提出采用锯齿形超声相控阵换能器进行电子旋转扫查检测的方法。为研究锯齿形超声相控阵探头的聚焦声场特性，首先根据射线声学原理，研究该换能器在圆弧形分界面条件下的延迟法则计算方法；其次采用有限元仿真方法分析该换能器超声声场的聚焦声场特性，结合动态光弹实验方法，对聚焦声场进行观测实验；最后在含有人工缺陷试块中进行检测实验。实验结果表明：通过设计相应的聚焦法则，可以实现电子控制声场周向扫查，在聚焦点附近声场能量增大，在远离聚焦点处声场能量减弱，瞬态观测实验声场聚焦效果与仿真结果相符，检测实验缺陷信号明显，无底波干扰。
Abstract：Serrated phased array transducers were used to detect longitudinal cracks on the outside surface of hollow shafts using electrical focus rotational scans. This paper describes the acoustic field characteristics of the serrated ultrasonic phased array transducers. The focus characteristics for a cylindrical fluid-solid interface was studied using the ray tracing method. Simulations with the finite element method (FEM) were used to evaluate the acoustic field in the shaft. Then, dynamic photoelastic experiments were used to study the focused transient acoustic field. Finally, detection experiments on a test block with artificial cracks showed that the serrated phased array transducers can rotationally scan the outside surface by using proper delayed time laws. The acoustic field energy was enhanced near the focus region, but decreased outside the focus region. The simulations matched the images acquired from the dynamic photoelastic experiment. The experiment shows that the crack signal was clear without interference from the back surface.