Last Updated on May 1, 2023 by You Ling
Introduction: The integration of piezoelectric composite materials in ultrasonic transducers has led to significant advancements across various applications. This article delves into the fundamentals of ultrasonic transducers, their working principles, and the diverse applications of piezoelectric composite materials in non-destructive testing (NDT), medical ultrasonics, underwater acoustics, air-coupled ultrasonics, flow measurement, and structural health monitoring.
1、Understanding Ultrasonic Transducers
An ultrasonic transducer is a device that converts electrical energy into ultrasonic waves, and vice versa. These waves are mechanical vibrations with frequencies above the human hearing range, typically greater than 20 kHz. Ultrasonic transducers have widespread use in industrial, medical, and scientific applications, such as non-destructive testing, medical imaging, and underwater communications.
2、The Working Principle of Ultrasonic Transducers
Ultrasonic transducers operate based on the principle of piezoelectricity. When an electric field is applied to a piezoelectric material, it undergoes mechanical deformation, producing an ultrasonic wave. Conversely, when an ultrasonic wave encounters a piezoelectric material, it generates an electrical signal. This property allows ultrasonic transducers to convert electrical signals into ultrasonic waves and vice versa.
3、Application of Piezoelectric Composite Materials in NDT Ultrasonic Transducers
In non-destructive testing, piezoelectric composite materials offer higher sensitivity and a better signal-to-noise ratio compared to conventional PZT materials. This improved performance allows for more accurate detection of flaws and defects in materials, making piezoelectric composite transducers an invaluable tool in quality control and structural integrity assessments.
4、Application of Piezoelectric Composite Materials in Medical Ultrasonic Transducers
In photoacoustic imaging, transducers made from piezoelectric composite materials exhibit significantly improved signal-to-noise ratios and bandwidth. In medical ultrasonics, shell-type focused transducers constructed from piezoelectric composites demonstrate reduced impedance and increased focusing intensity, resulting in clearer and more accurate diagnostic images.
5、Application of Piezoelectric Composite Materials in Underwater Acoustic Transducers
Underwater acoustic transducers made from piezoelectric composite materials offer several advantages, including higher sensitivity and increased hydrostatic piezoelectric constants. These features make piezoelectric composite transducers highly effective for underwater communication and sensing applications, such as sonar systems and oceanographic research.
6、Application of Piezoelectric Composite Materials in Air-Coupled Ultrasonic Transducers
Piezoelectric composite materials provide better acoustic impedance matching, thus improving the penetration of sound waves in air-coupled ultrasonic transducers. By using piezoelectric composites and a dual-matching layer structure, a gradual transition of acoustic impedance between the piezoelectric material and air is achieved, enhancing the acoustic energy transmission rate and the sensitivity of air-coupled ultrasonic transducers.
7、Application of Piezoelectric Composite Materials in Flow Measurement
Piezoelectric composites exhibit high piezoelectric voltage constants and have minimal impact on the performance of a structure when combined with a base material. These materials respond rapidly to changes in mechanical stress or strain, making them ideal for use as sensing elements in flow measurement applications.
8、Application of Piezoelectric Composite Materials in Structural Health Monitoring
Entering the 21st century, sensors have become a core component of structural health monitoring systems. Commonly used sensors include fiber Bragg grating sensors and shape memory alloy sensors. However, these sensors come with limitations, such as high information collection costs, susceptibility to environmental influences, and complex, low-precision signals. Sensors made from piezoelectric composite materials have overcome some of these challenges to a certain extent, offering a more reliable and cost-effective alternative for structural health monitoring.
9、Conclusion
Compared to piezoelectric ceramics (PZT), piezoelectric composite materials possess superior flexibility, higher mechanical strength, easily matched acoustic impedance, and a broader frequency response range. When compared to piezoelectric polymers (PVDF), piezoelectric composites feature simpler manufacturing processes and higher piezoelectric activity.
The integration of piezoelectric composite materials in ultrasonic transducers has significantly improved their performance and capabilities across a wide range of applications, including non-destructive testing, medical ultrasonics, underwater acoustics, air-coupled ultrasonics, flow measurement, and structural health monitoring. These advancements promise to pave the way for further innovations and developments in these industries.
