基于提高小尺寸复杂结构零件的超声检测的精确性的目的，采用时域有限差分法，分别建立了带有一个和3个圆形空腔的铝板模型，研究了不同铝板宽度下结构耦合对超声传播的影响。研究结果表明，对于两种结构的铝板，当宽度小于8个波长（20 mm）时，超声通过空腔的透射功率明显增大，其最高相对变化分别为10.5倍和6倍左右。这说明当铝板宽度与波长可比拟时，空腔与铝板之间有明显的耦合效应，且空腔的增加削弱了这种耦合效应，使得铝板宽度变化对超声传播的影响减弱。%To improve the accuracy when conducting ultrasonic detection for small-sized and complex-structure elements, two aluminum plate models with one cavity and three cavities were established and the structure coupling impacts on ultrasonic transmission under different sample sizes were analyzed by the finite-difference time-domain method (FDTD). The results show that for the two plates, the transmitted ultrasonic power through the cavities increases obviously when the width is less than 8 times (20 mm) of the ultrasonic wavelength, and its maximum relative change is up to 10.5 times and 6 times, respectively. This shows that, the coupling effect between cavity and aluminum plate is strong when the width is a few wavelengths. Also, the adding of the cavities will weaken the coupling effect, and the effect of size change on ultrasonic transmission properties will decrease.
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