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In the present study the discrete element method is used for predicting forces reactions and soil behavior during non-inversion tillage. The numerical model at particle level works with a force system integrated by normal, shear, cohesion and friction forces. Macro parameters are defined as the soil mechanical properties obtained by soil mechanical tests. The behavior of soil-soil and soil-metal interface at different dry bulk densities and gravimetric water contents were determined by modified direct shear box and triaxial compression tests. A set of statistical regression equations feasible to estimate the macro values of Young's modulus, shear strength, soil friction and soil cohesion were obtained. The relationship between macro and micro behavior of soil friction was investigated by means of the simulation of direct shear tests. The discrete soil model was used to simulate soil tillage at conditions called hard-dry, soft-wet and friable state. To calibrate the model, a soil-bin was filled with the soil previously characterized and equipped with a tool similar to the one used for the simulation. A National Instrument Data Logger system was configured aimed at measuring vertical and horizontal reaction forces. The comparison between draft forces from simulation and soil-bin tests showed a small under-predicted behavior of the model for loose soil with high moisture; this behavior was fixed toward compacted and dry soil conditions. Para-plough and moldboard were the tools used for non-inversion tillage simulation at different physical states of the soil. The result shows the pattern of movement and force distribution related with the geometry of the tool. [ABSTRACT FROM AUTHOR]

The paper aims at developing a validated model that can accurately predict the flow of a particulate material. This model will serve as a virtual design tool for the design of a novel passive safety system for nuclear reactors. Therefore an experimental setup consisting of a vertical glass tube is filled with 500±30 μm spherical glass particles. The experiment is then placed in a vacuum and the particles are released by opening a valve. The velocity of the particles is recorded during their fall at three different heights using a non invasive optical tracking technique with an original implementation. The same experiment is then simulated using the Discrete Element Method and results are compared. A good agreement between the simulation and the experiment was found. The sensitivity of the simulation to a change in the contact stiffness, dynamic Coulomb coefficient of friction and tangential contact force model was investigated. The influence of the initial position of the simulated particles on the packing factor was shown to be very important. Finally the experiment proved to be extremely sensitive to a perturbation of the outflow section of the tube, something that was predicted by the simulations. [ABSTRACT FROM AUTHOR]

Friction and cohesion in efforts that take place during soil deformation calculations. For interactions are considered normal force, tangential cohesive friction. The maximum shear is governed by the criterion of Mohr-Coulomb failure. Model calibration is performed by obtaining the relationship between micro and macroscopic parameters used in the model. The calibration of the friction was carried out by simulating the direct shear test of a sample of soil micro different friction coefficients. To calibrate cohesion used different values of cohesion at the micro and the relationship was obtained by modifying the micro friction values by simulating the biaxial compression test. The friction results showed a linear relationship regarding the variation of the micro value. Instead cohesion was linearly affected by the change in the quadratic micro-cohesion and friction over micro. [ABSTRACT FROM AUTHOR]