Vibration amplitude and induced temperature limitation of high power air-borne ultrasonic transducers

• Vibration and induced temperature of airborne ultrasonic transducer investigated theoretically and experimentally.
• Vibration amplitude in last matching layers is very large. This large amplitude is cause of damage of transducer.
• Appropriate matching layers, lost power, temperature distribution are determined.
• Induced temperature due to the large amplitude is more than melt point of last matching layers.
• In high power airborne ultrasound, the internal loss plays a key point and must be considered in design.

The acoustic impedances of matching layers, their internal loss and vibration amplitude are the most important and influential parameters in the performance of high power airborne ultrasonic transducers. In this paper, the optimum acoustic impedances of the transducer matching layers were determined by using a genetic algorithm, the powerful tool for optimizating domain. The analytical results showed that the vibration amplitude increases significantly for low acoustic impedance matching layers. This enhancement is maximum and approximately 200 times higher for the last matching layer where it has the same interface with the air than the vibration amplitude of the source, lead zirconate titanate-pizo electric while transferring the 1 kW is desirable. This large amplitude increases both mechanical failure and temperature of the matching layers due to the internal loss of the matching layers. It has analytically shown that the temperature in last matching layer with having the maximum vibration amplitude is high enough to melt or burn the matching layers. To verify suggested approach, the effect of the amplitude of vibration on the induced temperature has been investigated experimentally. The experimental results displayed good agreement with the theoretical predictions.