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Discrete Element Modeling of Soil-Implement Interaction Considering Soil Plasticity, Cohesion and Adhesion

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  131618800,  2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: @2013
Authors:   John M Fielke, Mustafa Ucgul, Chris Saunders
Keywords:   DEM draft force simulation sweep vertical force.

Abstract. Modeling of soil-implement interactions is a complex process due to the variability of the soil profile, non-linear behavior of the soil material and the dynamic effect of the soil flow. An approach that gives a further insight is the technique of discrete element modeling (DEM). Although ample eminent research has been conducted regarding modeling of the soil-implement interaction in 2D, there is just a few studies regarding to 3D modeling of the soil-implement interaction. Although cohesion was taken into account in the available 3D DEM studies, there is no study that considers both soil adhesion and cohesion. Additionally, in the available 3D DEM studies soil particle contacts were assumed as pure elastic, which is not realistic. As such most of the available literature has been focused on draft forces with no satisfactory prediction of the vertical forces. In this study a DEM model is presented that considers the plasticity, cohesion and adhesion of the soil. The approach to determine the required DEM parameters was to firstly model a non-cohesive soil with elastic/plastic contacts that does not adhere to the tool and to then include cohesion and adhesion to the model. The DEM parameters for a non-cohesive soil were determined by performing and then simulating an angle of repose and two penetration tests. Cohesion and adhesion was added to the model using cohesive energy density values between particle/particle and particle/tool, respectively. The validation of the model for a cohesive soil was carried out using shear box tests and simulations in terms of three different levels of moisture contents of 4, 8, and 12% for a sandy loam soil. The parameters; namely coefficient of friction, coefficient of rolling friction, and integration time, were determined using a trial and error approach for a 10 mm radius spherical particle. EDEM software was used in the simulations. As a last step of the study, the interaction between the soil and a sweep tool which was experimentally studied by Fielke (1988) was simulated. A good correlation was obtained between the measured and predicted draft and vertical forces showing that the method proposed is valid.

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