Tang Yifan, Lin Shuyu
Shaanxi Key Laboratory of Ultrasonics, Institute of Applied Acoustics, Shaanxi Normal University, Xi'an 710119, PR China.
Shaanxi Key Laboratory of Ultrasonics, Institute of Applied Acoustics, Shaanxi Normal University, Xi'an 710119, PR China.
Ultrasonics. 2024 Jan;136:107155. doi: 10.1016/j.ultras.2023.107155. Epub 2023 Sep 3.
Spherical piezoelectric transducers are a critical component of ultrasonic vibration systems with significant applications in various practical scenarios such as underwater acoustic detection and structural health monitoring. The existing spherical piezoelectric transducers have fixed electromechanical characteristics that limit their applications in scenarios with multi-frequency or frequency variation requirements. It would therefore be intriguing, from the viewpoints of both science and technology, to break through this limit by introducing external electric load impedance. Here we propose a tunable spherical piezoelectric transducer (TSPT) capable of adjusting the electromechanical characteristics by changing the resistance, inductance, and capacitance applied to the passive piezoceramic shell. The theoretical and numerical results show that when the resistance is exerted on the inner and outer piezoceramic shells, the resonance is accompanied by large variations at low values of resistance, while it becomes almost constant at high values of resistance. When the inductance is exerted on the outer piezoceramic shell, the resonance frequency obtained by the finite element method can be changed from 72730 Hz to 42928 Hz by adjusting the inductance, indicating that the TSPT can realize a rich and selective resonance frequency region. The resonance/antiresonance frequency decreases while the effective electromechanical coupling coefficient increases, when the capacitance applied on the inner and outer piezoceramic shells increases. The experiments are conducted to verify the effectiveness of the proposed TSPT, which is in agreement with the simulated results and theoretical predictions. Our methodology will offer possibilities to extend the working frequency range of the existing piezoelectric spherical transducer for underwater acoustic detection, hydrophones, and the spherical smart aggregate for civil structural health monitoring.
球形压电换能器是超声振动系统的关键部件，在水下声学探测和结构健康监测等各种实际场景中具有重要应用。现有的球形压电换能器具有固定的机电特性，这限制了它们在多频率或频率变化要求场景中的应用。因此，从科学和技术的角度来看，通过引入外部电负载阻抗来突破这一限制将是很有趣的。在此，我们提出一种可调谐球形压电换能器（TSPT），它能够通过改变施加在无源压电陶瓷外壳上的电阻、电感和电容来调整机电特性。理论和数值结果表明，当电阻施加在内、外压电陶瓷外壳上时，在低电阻值时共振会伴随较大变化，而在高电阻值时共振几乎保持不变。当电感施加在外压电陶瓷外壳上时，通过有限元方法获得的共振频率可通过调整电感从72730 Hz变为42928 Hz，这表明TSPT可以实现丰富且具有选择性的共振频率区域。当施加在内、外压电陶瓷外壳上的电容增加时，共振/反共振频率降低，而有效机电耦合系数增加。进行了实验以验证所提出的TSPT的有效性，实验结果与模拟结果和理论预测一致。我们的方法将为扩展现有压电球形换能器在水下声学探测、水听器以及用于土木结构健康监测的球形智能骨料方面的工作频率范围提供可能性。
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