Xu Ke ^{1, 2}, Xu Zuquan ^{1, 2}, Bu Fanqiang ^{1, 2}, Wu Yufu ^{1, 2}, Wang Xingguo ^{1, 2},

Li Xiaogao ^{1, 2}, Zhang Guoqin ³, Tang Guoxing ^{1, 2}

(1. School of Mechanical and Electronic Engineering, Jingdezhen Ceramic University, Jingdezhen 333403, Jiangxi, China;

2. Industrial Technology Engineering Center for Ceramic Material Processing Technology, Jingdezhen 333403, Jiangxi, China; 3. Jiangxi Xinhang Aviation Technology Co., Ltd., Jingdezhen 333403, Jiangxi, China)

Extended abstract:

[Background and purposes] Silicon carbide ceramics are widely used in aerospace, semiconductor manufacturing, precision molds and other advanced engineering fields, because of their excellent hardness, wear resistance, thermal stability and chemical inertness. However, their high hardness and brittleness make conventional machining processes difficult, often resulting in severe tool wear, low machining efficiency and poor surface quality. Ultrasonic vibration-assisted machining technology can be employed to effectively reduce cutting resistance and improve the machining performance of brittle materials. In this study, an ultrasonic longitudinal-torsional composite vibration system suitable for silicon carbide ceramic machining was designed and optimized. The influence of helical groove structures on vibration characteristics of the transducer was analyzed, while the effects of temperature, excitation voltage and bolt preload on performances of the ultrasonic system were systematically studied to provide theoretical and experimental support for high-efficiency ultrasonic machining of ceramic materials.

[Methods] A longitudinal-torsional ultrasonic transducer and machining tool were designed based on ultrasonic vibration-assisted machining principles. Finite element simulations were carried out using ANSYS software to study the influence of helical groove structures on vibration characteristics and dynamic response of the transducer. Modal analysis and harmonic response analysis were used to determine the resonant frequency and vibration amplitudes of the ultrasonic tool. In addition, the effects of temperature, excitation voltage and bolt preload on the equivalent electrical parameters, including resonant frequency, dynamic inductance, static capacitance, dynamic capacitance and dynamic resistance, were systematically analyzed. Experimental tests were further conducted to verify the simulation results and evaluate the vibration performance of the developed ultrasonic machining system.

[Results] The helical groove structure has a significant influence on the generation of torsional vibration and the longitudinal-torsional amplitude ratio of the ultrasonic machining tool. The resonant frequency of the developed ultrasonic tool was measured to be 21634 Hz, which was close to the simulation result. The longitudinal vibration amplitude reached 7.8 μm, while the torsional vibration amplitude was about 2.4 μm, with a torsional-to-longitudinal amplitude ratio of 0.3. As the temperature increased, the resonant frequency and dynamic inductance decreased, while the static capacitance and dynamic capacitance increased. The dynamic resistance first increased and then decreased with rising temperature. The temperature rise during operation was highest in the rear cover plate, followed by the piezoelectric ceramic section and the front cover plate. With increasing bolt preload, the static capacitance, dynamic capacitance and resonant frequency increased, whereas the dynamic inductance and dynamic resistance decreased. In addition, both longitudinal and torsional vibration amplitudes increased with increasing excitation voltage.

[Conclusions] An ultrasonic longitudinal–torsional composite vibration system suitable for machining silicon carbide ceramics was successfully designed and optimized. The simulation and experimental results demonstrate that the helical groove structure can effectively realize longitudinal-torsional vibration coupling and improve the vibration characteristics of the ultrasonic machining tool. Temperature, excitation voltage and bolt preload significantly affect the electromechanical properties and operational stability of the transducer. The ultrasonic tool exhibits stable resonance characteristics and satisfactory composite vibration performance, which can effectively improve the machining capability of hard and brittle ceramic materials. This study can be used as important theoretical guidance and practical reference for the design and application of ultrasonic-assisted machining systems for advanced ceramics.

Key words: silicon carbide ceramic; longitudinal-torsional composite vibration; finite element analysis; ultrasonic machining tool