A high-performance longitudinal-bending ultrasonic vibration horn: structural innovation and dynamic testing

In rotary machining, cutting tools are generally designed as axisymmetric structures to ensure dynamic balance. Traditional longitudinal-bending composite ultrasonic vibration horns with single-source excitation feature non-axisymmetric configurations due to the eccentric placement of mass blocks. Owing to the significant mass eccentricity, such horns cannot achieve dynamic balance merely by adjusting counterweight holes. As a result, these longitudinal-bending composite vibration horns are unsuitable for application in rotary ultrasonic vibration-assisted grinding (RUVAG) systems. However, various non-axisymmetric structures, such as those resembling cam-crank mechanisms, have been successfully utilized in rotary motion. These configurations achieve dynamic balance through ingenious structural designs and strategic spatial distribution. Inspired by this principle, a novel design was proposed to enable longitudinal-bending composite vibration in a non-axisymmetric horn structure, while simultaneously satisfying the dynamic balancing requirements during rotation. By integrating dynamic balancing theory with wave theory, the horn structure was mathematically modeled and optimized through finite element analysis. Experimental investigations were conducted to validate the vibration performance of the horn and to evaluate the effects of cam geometry and ultrasonic generator power on its vibration behavior. In the present study, two cam-profile horns with distinct geometric dimensions were designed and manufactured. The experimentally measured resonant frequencies were 21,640 Hz and 21,517 Hz, exhibiting relative errors of 0.478 % and 0.728 %, respectively, when compared to the simulated results. The measured longitudinal vibration amplitudes were 1.74 μm and 5.14 μm, while the corresponding bending amplitudes were 0.24 μm and 2.89 μm. The relative errors between the experimental and simulated amplitudes were 7.15 %, 8.86 %, 11.11 %, and 13.77 %, respectively. Experimental results demonstrate that the cam dimensions of the cam-profile horn significantly influence both longitudinal and bending vibration amplitudes. Specifically, increasing the cam ratio leads to enhanced vibration amplitudes. Moreover, elevating the output power of the ultrasonic generator further amplifies both modes of vibration. The proposed cam-profile horn exhibits superior vibration performance and precise amplitude controllable capability.