Research of quality during drilling of CFRP with ultrasonic-assisted machining

Abstract

In this study, an ultrasonic tool holder was designed and improved based on traditional tool holder designs to process the difficult-to-machine materials, such as carbon fiber composite materials. The design incorporated a variable cross-section ultrasonic horn and a core-clamped piezoelectric transducer with dimensions calculated by MATLAB R2021b based on the equivalent circuit method. Focusing on the longitudinal vibration ultrasonic knife handle, ANSYS 2022R1 was used to conduct finite element modal and harmonic response simulations to determine the resonant frequency of the tool holder. After the assembling of the tool holder, the experimental testing was conducted to determine the resonant frequency, resistance, effective electromechanical coupling coefficient, etc. The experimental results are compared with the simulation outcomes to validate the accuracy of the design. The amplitude of the ultrasonic tool holder was measured using a Doppler laser vibrometer, revealing a resonant frequency of 20260 Hz and a front-end amplitude of 10 μm, which aligned with the simulations. the ultrasonic tool holder was then connected to the spindle interface of the machine tool and installed on the ultrasonic combined machine tool. Power and cutting force testing were performed on a carbon fiber reinforced polymer/plastic (CFRP) composite plate using a force measuring instrument. The experimental results show that the amplitude of the ultrasonic knife increases linearly with ultrasonic power, and the force on the composite plate gradually decreases at constant speeds and feeds. When the reference powers were set at 40%, 60%, and 80%, the axial force exerted by the ultrasonic tool holder during drilling was lower compared to concentional tool holders,yielding favorable machining results. Moreover, results demonstrate that the ultrasonic-assisted processing enhances the cutting efficiency and quality of CFRP composite materials.