Modeling the process of belt feeding of seedlings in a forest planting machine based on the discrete element method

Designing belt seedling feeding mechanisms for forest planting machines requires ensuring a reliable grasp without damaging the living tissues of the planting material. Traditional field-testing methods for optimizing this process are resource-intensive. The purpose of the research is to develop and apply the discrete element method (DEM) to create a detailed virtual model of the belt feed process, which allows for parametric analysis of the force effect. The comprehensive DEM model was developed in the research. It integrates three subsystems: the discrete structure of the rubber belt (Kelvin-Voigt elastic-viscous model), the multifarious model of the seedling, taking into account bending forces, and the precise geometry of the roller mechanism. The model is implemented in a specialized software complex. The main analyzed parameter was the force of transverse compression of the seedling by the belts (F_c). Verification confirmed the physical correctness of the model. The spatio-temporal distribution of force F_c with pronounced maxima (up to 13.5 N) in the contact zones with the rollers has been established. The minimum value of the force (7.5 N) guarantees reliable traction throughout the entire trajectory. Comparison of peak force with the threshold for damage to the tissues of coniferous seedlings (15-18 N) showed a strength margin of >20%. Parametric analysis revealed a statistically significant increase in the average force by 7.8% with an increase in the belt speed from 0.5 to 1.0 m/s. The developed DEM model is an effective tool for virtual prototyping. It allows for multi-variant analysis and optimization of the structural and operating parameters of the belt mechanism, ensuring a balance between grabbing reliability and seedling biomechanical safety, which reduces the costs of experimental design work.