弯曲振动超声换能器的振动特性及辐射声场研究

Vibration and radiation characteristics of air-coupled flexural ultrasonic transducers

对弯曲振动气介式超声换能器的振动特性及辐射声场进行了研究.该换能器由中心激励的弯曲振动圆盘及纵向振动夹心式压电陶瓷换能器组成.对圆板的轴对称弯曲振动进行了分析,得出了边界简支薄圆板的共振频率方程,推出了夹心式换能器与弯曲圆盘复合振子的机电等效电路及总体频率方程,并求出了其辐射远场声压分布指向性的解析表达式及换能器辐射近场的三维声压分布.结果表明,弯曲圆盘换能器的近场声压分布同样具有指向性,且主要分布在与换能器横向尺寸相同的空间内.对于弯曲振动圆板不同振动模式,等效电路参数及声场分布和指向性不同.

The vibration and radiation acoustic field of aircoupled transducers in flexural vibration are studied. The radiator of the aircoupled transducer is a circular thin plate in flexural vibration with a simply supported boundary condition. The axially symmetric flexural vibrational mode of the circular thin plate is analyzed. The resonance frequency equation of the circular radiator with a simply supported boundary condition is derived and the equivalent circuit of the circular thin plate in flexural vibration is obtained. The near and far acoustic field of the circular thin plate radiator in flexural vibration is analyzed. In the near acoustic field, the threedimensional acoustic pressure distribution of the circular radiator in flexural vibrational mode is computed. In the far acoustic field, the twodimensional directivity pattern in polar coordinates is obtained theoretically. From the results it can be seen that the near acoustic field is limited to a region that is equal to the surface area of the radiator, and the near acoustic field is also directional. When the vibrational order of the circular thin plate in flexural vibration is increased, the near and far acoustic fields become complex. This is different from the acoustic field generated by an oscillating piston. 