Modeling the soil heterogeneity in the discrete element model of soil-sweep interaction

In agriculture the analyse of soil compaction in soil-tool interaction has a significant role. The equipments of agricultural farms are getting bigger and more complicated and it has huge importance to optimize the tillage methods. Two of most frequently investigated factors are the tool’s mixing-effect and the draught force on the tool; these results are important for agronomical experts to design tillage tools and cultivation processes. Discrete element method (DEM) is one of the numerical methods to model soil’s behaviour and soil-tool interaction. Aim of this study is to develop a 3D DEM model for clay soil and analyse the behaviour of soil- model regarding to non-homogeneous soil condition of agricultural fields. Simulation results will be compared with field test measurements for cone penetration tests. In this paper effects of particle’s shape and micromechanical properties will be investigated and simulations will be compared using special particles, so-called clumps in model. Clumps are aggregations that are set of spheres. This study investigates the effect of using clumps instead spheres in simulations and it will be attempted to model the thixotropic behaviour of soil with special kind of particles. Non-homogeneous property and varied compaction of field soil will be modelled with more layers, keep to be comparable the simulation results with field tests. Measurements were set for content; study investigates appropriate set of micromechanical parameters to simulate the effect of water

Laboratory and numerical investigation of direct shear box test

In agriculture, food, chemical, plastic and pharmaceutical industries for designing and operating machines, it is essential to determine the mechanical parameters of the processed granular materials. In most cases, these characteristics are the internal friction angle, the contact cohesion developed by the surface moisture and the apparent cohesion occurred by the shape of the granular material. Further physical quantities are required to characterize the motion state of the particles, which were determined by laboratory measurements in this study. Hulled mil- let was used for the measurements because its geometric shape can be modeled as sphere in the numerical investigations with good approximation. The porosity, the particle and bulk den- sity of the hulled millet were determined by means of an air pycnometer in case of several moisture content. Using laboratory direct shear box test, under standard conditions, the shear strength of the cohesive liquid bridges and the internal friction angle in the bulk were deter- mined. The results obtained were used for input parameters of a discrete element model. The aim of this research was to determine the micromechanical parameters by simulation, based on the macromechanical results of the hulled millet bulk during laboratory measurements

The Evaluation of the Parallel Bond’s Properties in DEM Modeling of Soils

In this study we conducted the sensitivity analysis of the parallel bond used in the discrete element method (DEM, 3D) based soil model. We researched those parameters which simulate real soil physique attributes. In our investigations we modeled the inhomogeneity by the differentiation in particle size, the soil moisture condition by the parallel bond’s radius R, the cracking tendency by the bonding stiffnesses kn, ks and the air phase by the pore volume of the particle block. We based the validation of the simulation on the results of the simple direct shear box test which were performed in laboratory environment. We analyzed the effect of micromechanical and macromechanical parameters, used in the modeled particle block, with the use of direct shear box and triaxial shear simulations. After the recalculation of micromechanical parameters (EC, ĒC, γ) we analyzed the effect of the adjustable macromechanical parameters (kn, ks ,λ, kn, ks, σC, τC) used in the block with triaxial shear simulation. Based on the comparison of the shear simulations’ results the accuracy of the recalculation of the parallel bond’s micro-macro parameters is proved by the good correlation of the Coulomb failure criterion lines (σ-τ)

Kiemelten nagyszilárdságú acél vékonylemezek ellenállás-ponthegesztett kötéseinek optimalizálása kísérlettervezési módszerrel

A kutatásunk során DP 800-as vékonylemezek ellenállás-ponthegesztett kötéseinek tulajdonságait optimalizáltuk Box-Wilson kísérlettervezési módszer segítségével. Az elsődleges célfüggvény a legnagyobb elérhető nyíró-szakítóerő volt. A kapott eredményekre matematikai válaszfelület alapú függvényt illesztettünk. A nyíró-szakítóerőre való optimálás eredményeképp az AWS D8.1M szabvány által előírt elfogadható nyíró-szakítóerő érték háromszorosát kaptuk. A többszempontú optimum esetén a nyíró-szakítóerő csak kismértékben, a benyomódás nagymértékben csökken

Series Wound DC Motor Simulation Applying MATLAB SIMULINK and LabVIEW Control Design and Simulation Module

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The Influence of the Soil Water Content in the Soil-Tool DEM Model

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 (Ec) and bonding (Ēc), 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 (ci). 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 (Kn = 1.73e4 N/m, Ks = 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 soil—sweep 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)

Simultaneous Dual Distal Radial Balloon Aortic Valvuloplasty for Larger Aortic Annuli

Dual distal mini-balloon aortic valvuloplasty stabilized an 85-year-old patient with severe aortic stenosis. Puncturing both radial arteries solves the issue of large diameters at the aortic ring, introducing a feasible strategy in selected cases of fragile octogenarian patients with a high hemorrhagic risk. Moving at the anatomical snuffbox offers better postprocedural occlusion rates and better workspace ergonomics during the procedure

Late Sodium Current Inhibitors as Potential Antiarrhythmic Agents

Based on recent findings, an increased late sodium current (INa,late) plays an important pathophysiological role in cardiac diseases, including rhythm disorders. The article first describes what is INa,late and how it functions under physiological circumstances. Next, it shows the wide range of cellular mechanisms that can contribute to an increased INa,late in heart diseases, and also discusses how the upregulated INa,late can play a role in the generation of cardiac arrhythmias. The last part of the article is about INa,late inhibiting drugs as potential antiarrhythmic agents, based on experimental and preclinical data as well as in the light of clinical trials