Several analytical methods of the soil-tool interaction have been developed and tested, but they are time consuming and require large effort, which has prevented their widespread use. This paper presents the development of a three dimensional (3-D) discrete element method (DEM) model for the simulation of soil-sweep interaction. The aim was to understand the effects of the sweep rake angle (β) and speed on draught and soil loosening. It implements computer aided design (CAD) systems to simulate the sweep geometry. The DEM model output was validated by comparing simulated and corresponding actual soil bin measurements using a cohesive wet sandy soil. Cohesion of the wet sandy soil was assigned using a parallel bond contact model, where the normal and shear stiffness of the bond, the normal and shear strength, and the size of the connecting geometry were the main parameters. Following the comparison between the simulated and measured draught based on input parameters measured with a direct shear box test, virtual DEM triaxial compression analyses were performed to refine the DEM model parameters including cohesion, internal friction angle, modulus of elasticity and Poisson's ratio, using the Mohr-Coulomb failure criterion.

This paper describes the mechanical modeling of rapeseed using the 3D Discrete Element Method (DEM

Abstract. The Discrete Element Method (DEM) for describing the action mechanism between soil and sweep tool can be used to perform a detailed analysis of draft force, soil cutting, clod-crushing and loosening by taking into account the tillage speed and the three soil phases. This study describes the simulation of the 3D DEM soil model and a cultivator sweep digitized with a 3D scanner, showing the soil-sweep interaction as a function of implement draft force and implement operating speed.The suitability of the model is validated by comparing the results of laboratory and simulated shear tests (static validation) with the results of soil bin tests (dynamic validation). The mechanical parameters of the sandy soil used for the soil bin tests were measured using the direct shear box test. Cohesion for the soil model used during simulations was set using the parallel bond contact model, where the determining factors were the Young modulus for particle contact (E c ) and bonding (Ē c ), the Poisson's ratio (nu), the normal ( ) σ and shear ( ) τ bond strength and the radius of the related volume (cylinder). Once the DEM model parameters were set, the draft force values measured during dynamic testing were harmonized using the value for viscous damping (c i ). The dynamic soil-sweep model was validated using the viscous damping applied based on the simulated and measured draft force values. The validation of the Young modulus to 0.55e6 Pa (K n = 1.73e4 N/m, K s = 8.64e3 N/m) enabled us to set the draft force values of the model for different speeds (0.8-4.1 m/s) with an accuracy of 1-4%.During the analysis of changes in tillage quality, the developed dynamic soilsweep model showed a high degree of porosity (48%) due to grubbing in the attenuated speed range (0.5-2.1 m/s), and a decreasing tendency (0.41-0.39%) in the non-damped speed range (2.1-4.1 m/s). After the initial equilibrium state, the ratio of average particle contacts for the given porosity decreased in the attenuated speed range (coord number: 4.8), and a slight decrease was also found above speeds of 2.1 m/s (coord number: 5.2). In the model, clod-crushing was examined based on the ratio of sliding contacts, and we found a continuous increase (sliding fraction: 2-15%) in the speed range used for the simulation (0.8-4.1 m/s).

In this study we conducted the sensitivity analysis of the parallel bond used in the discrete element method (DEM, 3D) IntroductionIt is important for the developing engineers of tillage machines to get fast and accurate feedback on the functionality and effectiveness of new constructions, because of the evolved market competition and the increasing needs of users. We can reconstruct field measurements by the investigations conducted in simulated environments. To investigate the micro-and macro cracks appearing in soils we need to use discrete element methods (DEM), instead of using continuous material models (FEM). Nowadays, because of the development of computer science, the DEM method is the most promising approach for modeling the soil-tool (sweep) interaction.In case of the soil-tool dynamic connection the cracks appearing in the soil affect greatly the size of the emerging deformation zone in front of the tool and thus the tool's towing resistance.It is hard to set the mechanical parameters of the "synthetic" materials used by the DEM method so as they are almost the same as the mechanical parameters of real materials [2]. Whereas the input parameters of continuum material models can be given directly from the results of laboratory measurements (Young's modulus, Poisson ratio, stress, etc.), the macro parameters of the material used in case of the DEM model depend on the features of the micro particles' connections. The input parameters in the DEM model are the parameters of the microscopic particles' connections (for example the spring stiffness between two particles, friction factor, etc.), that is why it is important to calibrate our model with the micro parameters. The parallel bond contact model was used to describe the liquid bridges between the soil particles and to set the so-called capillary effect in the model. The use of the parallel bond contact model enables the realistic cohesion in the DEM model.The micro parameters of the particle connections k k k k

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