Amplitude attenuation study and prediction model for large-load ultrasonic vibration systems: revealing the multi-factor coupling attenuation mechanism and stabilization strategies.

Ultrasonic Vibration-Assisted Machining (UVAM) is widely used for difficult-to-machine materials due to its high efficiency, low damage, and precision. However, load-induced forces between tool and workpiece cause amplitude attenuation during machining, compromising machining quality and tool life. To address this, this study establishes an amplitude prediction model based on equivalent circuit theory, integrating the horn's one-dimensional longitudinal vibration wave equation and piezoelectric constitutive equations, which correlates the tool axial amplitude with transducer electrical parameters (voltage, current, phase difference). A loading test platform was built for experiments with different load types (axial/radial), materials (aluminum/aluminum nitride), and magnitudes. Results show the model has high accuracy: maximum error within 0.7 μm under no-load and within 0.5 μm under load. Axial loading induces significant amplitude attenuation (up to 83.3% for hard-brittle materials) and resonant frequency shift, while radial loading has minimal impact; hard-brittle material loads cause more severe attenuation than metallic ones. Based on the results, the multi-factor coupling mechanism of the attenuation was revealed, which arises from the synergistic effects of resonant frequency detuning, horn vibration modal distortion, load material property coupling and the system's intrinsic nonlinear characteristics, and two stabilization strategies are proposed: reducing system quality factor to broaden bandwidth, and presetting excitation frequency to the right of no-load resonance. This study provides a reliable theoretical basis for amplitude monitoring and stability optimization of ultrasonic vibration systems under large-load machining.