Evaluation of the significance of the contact model particle parameters in the modelling of wet soils by the discrete element method

Modelling of the tillage process by working tools based on the method of discrete elements is currently the most promising. The results of modelling the processing process obtained by the method of discrete elements adequately describe the behaviour of the soil. Due to the large number of physical and mechanical parameters included in the description of contact models of discrete elements, the calibration process takes a lot of time. Thus, we set a research goal - to evaluate the significance of the parameters of the contact model particles in soil modelling by the discrete element method and to obtain nomograms for selecting the parameters of the Hertz-Mindlin contact model particles depending on the humidity of various types of soils. The article presents the results of calibration of the physical and mechanical parameters of the particles of the soil medium model described by the discrete element method. An improved Hertz-Mindlin JKR model was used as a contact model, the model was implemented in the Rocky DEM programme. The following properties of the modelled particles are taken as the studied factors – Poisson's ratio, static and dynamic friction coefficients, Jung's modulus, surface energy, and particle diameter. The detection of the natural slope angle of the soil was carried out for black soils of clay, light loam and sandy loam mechanical composition. The calibration was performed according to the angle of the natural slope. Comparison of the simulation results with field experiments of typical soils made it possible to establish that the nature of the change in the angle of the natural slope of the simulated soil environment is significantly affected by the surface energy and the diameter of the particles. The obtained dependences of the angle of natural slope on soil moisture and surface energy allow determining the parameters for the Hertz-Mindlin contact model as a function of humidity for Black soil zones of clay, light loam and sandy loam mechanical composition. Based on the results of field and model experiments, a nomogram was obtained that makes it possible to select parameters for the contact model - the diameter of soil particles and the value of surface energy depending on humidity and soil type. The obtained values of the parameters of the particles of the soil medium make it possible to simulate the process of tillage, optimize the design and technical parameters of the newly created working parts of tillage machines. • Purpose of the research is to assess the significance of the contact model particles. • Modelling of the tillage process by working tools is currently the most promising. • It is necessary to calibrate the rheological parameters of the contact models.