Application Cases

Research Direction: Ultrasonic Transducers

Test Objective:
Utilizing the inverse piezoelectric effect of piezoelectric ceramics and based on the design theory of sandwich piezoelectric ultrasonic transducers, a longitudinal vibration mode ultrasonic transducer suitable for rotary ultrasonic milling was designed. Simulation studies on factors influencing the resonant frequency of the ultrasonic transducer were conducted using PZFlex simulation software. The results indicated that the resonant frequency of the ultrasonic transducer decreases with increasing effective tool length and transition cylinder length, and increases with increasing preload bolt length and rear end cap hole depth. Based on the simulation results, a longitudinal vibration mode ultrasonic transducer was fabricated. Impedance analysis of the transducer was performed, and its resonant frequency was measured to be 17.41 kHz. The error between the resonant frequency measured on the physical prototype and that predicted by the simulation model was 5.7636%. Finally, based on the measured resonant frequency, the longitudinal amplitude output of the transducer under 200 V voltage excitation was measured to be 2.016 μm, which meets the requirements for rotary ultrasonic milling, thus validating the effectiveness of the model and providing a basis for further optimization design of ultrasonic transducers.

Figure: Physical Model of the Longitudinal Vibration Ultrasonic Transducer

In the development of ultrasonic vibration devices, the Japanese Ultrasonic Industrial Company has developed the USSP series ultrasonic spindle systems, characterized by small size, light weight, high rigidity, and suitability for installation on metal cutting machine tools. Researchers at the Kanazawa Institute of Technology in Japan have developed an ultrasonic low-frequency vibration combined drilling system for processing hard and brittle materials. Southeast University has designed a novel ultrasonic vibration cutting system. In this system, a generator outputs a voltage to cause a cascade crystal to undergo ultrasonic mechanical expansion and contraction, directly driving a resonant tool holder to achieve ultrasonic vibration, with an electromechanical conversion efficiency reaching 90%. Northwestern Polytechnical University has developed an ultrasonic vibration grinding device suitable for machining hard and brittle materials on an internal grinding machine. This device has a simple structure, low cost, and is suitable for production and processing applications. Currently, research on rotary ultrasonic machining both domestically and internationally is primarily focused on experimental studies. There is relatively little research on the design of rotary ultrasonic machining devices, and particularly, there is a lack of experience that can be referenced in the design process of rotary ultrasonic milling devices. Based on this, this paper designs a longitudinal vibration mode ultrasonic transducer and verifies its vibration characteristics through simulation and physical experimentation.

Testing Equipment: ATA-4052 high-voltage power amplifier, impedance characteristic analyzer, Doppler laser vibrometer, signal generator, oscilloscope, etc.

Experimental Procedure:
To further verify the simulation results, an impedance characteristic analyzer was used to perform impedance testing on the transducer. The test results, shown in the figure below, indicate that the resonant frequency of the transducer is 17.4113087 kHz, with an error rate of 5.7636% compared to the simulation result.

Figure: Transducer Impedance Test Results

Based on the resonant frequency test results of the ultrasonic transducer, a Doppler laser vibrometer was used to measure the longitudinal amplitude output at a reference point defined in the transducer simulation. The displacement range of the Doppler laser vibrometer was set to 200 nm/V. The excitation frequency of the signal generator was set to 17 kHz (typically slightly lower than the resonant frequency) with a voltage of 10 V. Measurements were performed after amplification by a factor of 20 using the ATA-4052 high-voltage power amplifier, resulting in a voltage of 200 V. The measurement results were output via a four-channel digital oscilloscope.

Experimental Results:
When the effective tool length was less than 60 mm, the resonant frequency of the ultrasonic transducer decreased with increasing effective tool length. The resonant frequency of the transducer increased with increasing bolt length. Increasing the length of the transition cylinder decreased the resonant frequency of the transducer. The resonant frequency of the transducer gradually increased with the depth of the countersunk hole in the rear end cap.

Impedance analysis of the transducer showed that the error between the resonant frequency of the physical model and the resonant frequency predicted by the simulation model was within an acceptable range.

Based on the resonant frequency measured from the physical model, the longitudinal amplitude output of the transducer was tested. The test results met the requirements for rotary ultrasonic milling, validating the effectiveness of the model.

Figure: Specifications of the ATA-4052C High-Voltage Power Amplifier