Analysis of the anti-adhesion mechamanism for the box surface shaping and profiling device in direct seeding of rape

Sticky clay soil has presented significant challenges to mechanized rapeseed planting in the rice-oil rotation regions of the middle and lower reaches of the Yangtze River. Conventional profiling mechanisms often struggle to maintain consistent bed shaping, leading to severe soil adhesion, gully formation, and clogging of the machinery. The stability of seeding depth is also limited to uneven seedbed surfaces, water accumulation, and waterlogging stress. There is high demand for the overall quality of rapeseed. In this study, the anti-adhesion mechanism of the whole profiling device was designed to fully meet the agronomic and mechanical requirements. A systematic investigation was conducted to determine the rotary compressing and shaping for the overall bed profiling. Mechanical-soil interaction of the rotary compaction was analyzed during the operation of a passive (non-driven) rotary roller. There was a decrease in the contact surface between the roller surface and the soil as the contact pressure increased, leading to inevitable soil accumulation and difficult detachment. In contrast, an active (driven) rotary roller was generated into the relative velocity difference between its surface and the seedbed. The bed was formed to exert a shearing and squeezing action on the roller surface in the forward rotation, leading to an active anti-adhesion mechanism. Conversely, the unformed soil on a reverse rotation roller was utilized to scour the roller surface—effectively preventing adhesion—the opposing motion and excessive grinding force tended to induce defects, such as surface cracks on the seedbed. A coupled DEM-MBD simulation was conducted to determine the velocity, displacement, and kinetic energy of soil particles adhered to the active roller. The microscopic interaction was visualized after simulation. As such, the soil adhesion primarily initiated in the contact zone with the unformed and loose soil, whereas the active anti-adhesion effect predominantly occurred in the contact zone with the compacted and formed bed. Subsequently, the bench tests were conducted to verify the simulation. In the forward-rotating roller, the soil adhesion area, adhesion volume, and bed surface roughness followed a trend of initially increasing and then decreasing as the rotational speed increased. Notably, the low anti-adhesion performance was found at the speed ratio of near 100% (where the linear velocity matched the forward speed). Therefore, the passive roller demonstrated low performance in both anti-adhesion and shaping quality. Furthermore, orthogonal bench tests were conducted to optimize the parameters, with the roller speed and absolute soil moisture content as experimental factors. The evaluation indices included the adhesion area, adhesion volume, and bed surface roughness. Results showed that the adhesion decreased with the high speeds of the reverse-rotating roller, whereas the bed surface roughness increased significantly, due to soil disturbance. The performance of adhesion depended on both rotational speed and soil moisture. Crucially, the forward-rotating roller demonstrated the superior adaptability to the variations in soil moisture content, compared with the other configurations. Finally, field trials were conducted in the post-rice stubble fields with sticky soil (absolute water content >30%). The forward active rotary roller was achieved in a soil adhesion area of 62.4 cm² and an adhesion mass of 174 g, which reduced the adhesion of 90.05% and 87.77%, respectively, compared with the passive roller. The bed surface roughness was recorded at 15.7 mm, which was improved by 86.08% over the passive counterpart. In contrast, the reverse-rotating roller also caused the excessive grinding of the bed surface. The forward-rotating active profiling mechanism can be expected for sticky soils. The finding can provide a strong reference for designing the seedbed preparation equipment in the Yangtze River basin.