Effects of Transverse Ultrasonic Vibration on Drag Reduction and Soil Disturbance in Soil Tillage: A DEM Investigation

Soil tillage is energy-intensive, and the cutting resistance of soil-engaging tools is its largest single loss. Ultrasonic vibration-assisted cutting (UVAC) can reduce this resistance, but quantitative studies have concentrated on longitudinal vibration; transverse vibration, which loads the soil by cyclic lateral squeeze and release, remains largely unexplored. A calibrated discrete element model of a transverse UVAC tool–soil system is developed to determine how amplitude, frequency and cutting speed govern drag reduction and to identify the contact-level origin of the effect. Bench tests at 20 kHz supplement the simulated design space with an additional operating condition and confirm the predicted forces at eight settings—five vibration conditions and three baselines—with a mean relative error of 8.7% and the baselines within 6%; one calibrated parameter set is used throughout. Over 30–70 µm, 25–45 kHz and 0.03–0.07 m s−1, amplitude dominates, raising the drag reduction from 44.10% to 68.18%, whereas frequency acts mainly through its quadratic term and its interaction with amplitude, and cutting speed enters the same coupling. Box–Behnken optimization places the optimum at 70 µm, 25 kHz and 0.07 m s−1, with a DEM-verified reduction of 69.25% against a predicted 69.53%. Contact analysis shows that the vibration shifts load from normal compression to tangential shear and converts bond failure from concentrated rupture into progressive degradation. Amplitude is therefore the primary design variable for transverse UVAC in sandy loam at 9% moisture, with frequency and speed modulating its expression.