13 research outputs found

    Effect of soil particle-size distribution (PSD) on soil-subsoiler interactions in the discrete element model

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    Aim of study: This work investigated the significance and mechanism for the effect of particle-size distribution (PSD) under different nominal radii using the discrete element method (DEM) and validated using the laboratory soil-bin results to accurately determine PSD.Area of study: Yangling, ChinaMaterial and methods: The experimental soil was Lou soil. Soil disturbance characteristics (soil rupture distance ratio, height of accumulated soil, soil density change rate) and cutting forces (draft and vertical) under different treatments were predicted and measured respectively.Main results: The ANOVA outputs showed that PSD significantly affected draft and vertical forces (

    A review of the Discrete Element Method/Modelling (DEM) in agricultural engineering

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    With the development of high-performance computing technology, the number of scientific publications regarding computational modelling of applications with the Discrete Element Method/Modelling (DEM) approaches in agricultural engineering has risen in the past decades. Many granular materials, e.g. grains, fruits and soils in agricultural engineering are processed, and thus a better understanding of these granular media with DEM is of great significance in design and optimization of tools and process in agricultural engineering. In this review, the theory and background of DEM have been introduced. Some improved contact models discussed in the literature for accurately predicting the contact force between two interacting particles have been compared. Accurate approximation of irregular particle shapes is of great importance in DEM simulations to model real particles in agricultural engineering. New algorithms to approximate irregular particle shapes, e.g. overlapping multi-sphere approach, ellipsoid, etc. have been summarized. Some remarkable engineering applications of the improved numerical models developed and implemented in DEM are discussed. Finally, potential applications of DEM and some suggested further work are addressed in the last section of this review

    Application of discrete element method in agricultural engineering

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    Basic principle of discrete element method was summarized, and commonly used software and its characteristics were introduced. Application of discrete element method in tillage, planting, harvesting and other agricultural machinery R & D was reviewed. Typical examples of application of discrete element method in agricultural machinery research and design at home and abroad were discussed and analyzed. Application prospect and trend of discrete element method in the field of agricultural engineering were prospected, in order to provide reference for further development of modern agricultural equipment digital design

    Improvement of the design of the plow-subsoiler-fertilizer to increase soil fertility

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    The authors have developed an original design of a plow-subsoiler-fertilizer. This combined working body includes a reversible plow and a vibratory subsoiler with fertilizer ducts. This solution allows you to combine the application of fertilizers when plowing the field, loosening the subsoil layer and mixing the soil. As a result of the work, the dependences of the geometric dimensions of the structure on the traction resistance to movement in the soil were obtained. Particular attention is paid to the calculation of the spring mechanism that ensures the vibration of the subsoiler. The optimal number and location of belleville springs in the block and shock absorber were selected, at which the subsoiler will perform self-oscillations with a given amplitude. Авторами разработана оригинальная конструкция плуга-рыхлителя-удобрителя. Этот комбинированный рабочий орган включает оборотный плуг и вибрационный глубокорыхлитель с тукопроводами. Такое решение позволяет совмещать внесение удобрений при вспашке поля, рыхлении подпочвенного слоя и перемешивании почвы. В результате работы были получены зависимости геометрических размеров конструкции от тягового сопротивления перемещению в грунте. Особое внимание уделено расчету пружинного механизма, обеспечивающего вибрацию глубокорыхлителя. Подобрано оптимальное количество и расположение тарельчатых пружин в блоке и амортизаторе, при которых глубокорыхлитель будет совершать автоколебания с заданной амплитудой

    Agricultural Structures and Mechanization

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    In our globalized world, the need to produce quality and safe food has increased exponentially in recent decades to meet the growing demands of the world population. This expectation is being met by acting at multiple levels, but mainly through the introduction of new technologies in the agricultural and agri-food sectors. In this context, agricultural, livestock, agro-industrial buildings, and agrarian infrastructure are being built on the basis of a sophisticated design that integrates environmental, landscape, and occupational safety, new construction materials, new facilities, and mechanization with state-of-the-art automatic systems, using calculation models and computer programs. It is necessary to promote research and dissemination of results in the field of mechanization and agricultural structures, specifically with regard to farm building and rural landscape, land and water use and environment, power and machinery, information systems and precision farming, processing and post-harvest technology and logistics, energy and non-food production technology, systems engineering and management, and fruit and vegetable cultivation systems. This Special Issue focuses on the role that mechanization and agricultural structures play in the production of high-quality food and continuously over time. For this reason, it publishes highly interdisciplinary quality studies from disparate research fields including agriculture, engineering design, calculation and modeling, landscaping, environmentalism, and even ergonomics and occupational risk prevention

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

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    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)

    A novel method for measurement of the angle of repose of granular seeds in discrete element methods

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    Discrete element numerical simulations can help researchers find potential problems in the design phase, shortening the development cycle and reducing costs. In the field of agricultural engineering, more and more researchers are using discrete element methods (DEM) to assist in designing and optimising equipment parameters. Model parameters calibration is a prerequisite for discrete element numerical calculations, and the angle of repose (AoR) is commonly used to calibrate the parameters. However, the measurement of AoR in DEM was not seriously considered in industrial or academic fields. In practice, AoR is measured manually, using 2D digital image processing or using a 3D scan. However, reliable and consistent measurements of AoR in DEM are rarely mentioned. This study suggests an accurate and consistent way to measure AoR in DEM using a novel method to read particle coordinate information directly from the data file; then, the AoR is calculated by linearly fitting the centre coordinates of the outermost particles. Influences of input variables on AoR acquisition are discussed through several examples using customised templates with known angles. Then a comparative study of the accuracy of the measurement of AoR in DEM and the reliability of the parameter calibration results by the manual measurement, 2D digital image processing, and algorithm proposed in this paper was conducted. In case studies with four seed materials, this method prevented the subjective selection of AoR, improved the identification accuracy, and increased the precision and accuracy of DEM calibration. In addition, the time consumption for obtaining AoR using the novel method for measurement is much less than that of 2D

    Using similitude theory and discrete element modeling to understand the effects of digging parameters on excavation performance for rubber tire loaders

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    The large sizes of mining equipment pose challenges for analysis using experiments or simulation. While scaled physical and simulation models can address this challenge, no previous work has explored how similitude theory and modeling can provide valid analysis of large equipment such as rubber tire loaders. The objective of this research was to apply similitude theory and discrete element modeling (DEM) to study the effect of different digging parameters on the penetration and the draft on the buckets of rubber tire loaders. The work sought to (1) test the hypothesis that the geometry of a rubber tire loader bucket and operating conditions significantly affects the resistive force (draft) and penetration; (2) test the hypothesis that different geometry orientations and operating conditions of a rubber tire loader bucket significantly affects draft and penetration; (3) apply DEM to scale models of rubber tire loader buckets to understand the effect of bucket geometry, orientations, and operating conditions on draft and penetration; and (4) evaluate the effectiveness of using discrete element models and similitude theory to predict draft and penetration. The results show that geometry, muckpile particle sizes, height above the floor, rake angle, speed, and motor power output are correlated to penetration and draft. This work has demonstrated that we can build valid DEM models for predicting at a larger scale. The chamfer angle of semi-spade bucket cutting blades significantly affects the draft on the buckets and 30° chamfer cut angle performs the best with the lowest peak resistive forces and energy consumption. The work finds that the forces observed during the rotation phase of the simulation are lower than the observed forces during penetration --Abstract, page iii

    Numerical modeling of machine-product interactions in solid and semi-solid manure handling and land application

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    The general objective of the research effort reported in this thesis was to develop the knowledge required to optimize the design and operation of solid and semi-solid manure handling and land application equipment. Selected physical and rheological properties of manure products deemed to have an influence on the performances of manure handling and land application equipment were measured and general trends were identified among the measured properties. Relationships were also established between the measured properties and the type of manure as well as its total solids concentration. Field experiments were carried out to evaluate the effects of selected mechanical configurations, operating parameters and product properties on the discharge of manure spreaders. The influence of the type of conveying system (scraper conveyor and system of four augers) and the velocity at which it is operated, the geometry of the holding system and the position of a flow-control gate were all included in the analysis. The discharge rates of the machines as well as the specific energy required by the unloading operations were measured. A numerical modeling method called discrete element method (DEM) was used to create virtual manure, a numerical model of the real product. The measured physical and flow properties were used to develop and validate the virtual manure models. It was found that manure products could successfully be represented in a DE framework and that several parameters defining the contact constitutive model in the DEM had an influence on the behaviour of the virtual products. The DEM was then used to study machine-product interactions taking place in handling and land application equipment. Results from field experiments carried out using various land application equipment were used in the development and validation of the interaction models. The predicted flow rates and power requirements were in good agreement with measured data. The results obtained allowed for a better understanding of the flow of manure products in manure handling and land application equipment. It was found that the constitutive model used for the product influenced the results of the machine-product interactions models. A precision banded applicator under development at the University of Saskatchewan was also modeled. The discharge rate of this equipment is influenced by a number of parameters. The predicted mass distribution across the width of the banded applicator was well correlated to the experimental results. The models developed in this thesis have the potential to become powerful engineering tools for the design of improved machines for the handling and land application of solid and semi-solid manure
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