Numerical Simulation of Spiral Cutter–Soil Interaction in Deep Vertical Rotary Tillage

Deep vertical rotary tillage (DVRT) is a new tillage method which combines the advantages of deep tillage and rotary tillage. However, limited research has been conducted on a critical component of the deep vertical rotary tiller, namely the spiral cutter. In clay loam, there are a lot of large clods in the topsoil layer after tillage, and the cutting resistance and vibration of the cutter are substantial. To reveal the reasons behind this, a simulation model of a spiral cutter–soil system was developed using Smoothed Particle Hydrodynamics (SPH). Using this model, the working process and force of a spiral cutter were thoroughly investigated. The results show that soil fragmentation, swelling, and loosening primarily result from the combined effects of the separation cutting, velocity difference cutting, auxiliary cutting, and the spiral blade’s lifting effect on soil. The reasons for the larger clods are that topsoil furrow slices are larger and the velocity difference cutting is insufficient. The substantial resistance of the cutter is mainly due to the greater resistance of the blade and the bottom edge, and too many blades cutting the soil simultaneously. Furthermore, due to the asymmetry of the cutter’s structure, the resistance’s amplitude reaches 1963.5 N, which causes the cutter’s large vibration. These findings would be an important basis for optimal cutter design.