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

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

Phosphorus nutrition of grain legumes in the semi-arid tropics

This book contains papers presented at an international workshop on this topic held at ICRISAT Center on 8-11 Jan 1990. The workshop was the culmination of a 5-year special project at ICRISAT funded by the Government of Japan. The first part of the book. covers phosphorus availability in soils of the semi-arid tropiCS (SAT). focusing on appropriate methods of measurement Then follows a section on mechanisms by which plant roots take up soil phosphorus. highlighting the role of root exudates. Specific root exudates of chickpea (Cicer arietinum L.) and pigeonpea [Cajanus cajan (L.) Millsp.] are described in detail. Subsequent chapters deal with options for improving the phosphorus nutrition of grain legumes. particularly chickpea and pigeonpea. in the SAT. Noteworthy are discussions on how to manipulate favorably mycorrhizal associaLions. Final chapters cover phospHorus fertilization from the point of view of entire cropping systems. Recommendations are made for a better understanding of the dynamics of phosphorus cycling in target cropping systems. and the need for better use of current knowledge in improving phosphorus fertilizer-use efficiency in these systems

A Review of Resonant Converter Control Techniques and The Performances

paper first discusses each control technique and then gives experimental results and/or performance to highlights their merits. The resonant converter used as a case study is not specified to just single topology instead it used few topologies such as series-parallel resonant converter (SPRC), LCC resonant converter and parallel resonant converter (PRC). On the other hand, the control techniques presented in this paper are self-sustained phase shift modulation (SSPSM) control, self-oscillating power factor control, magnetic control and the H-∞ robust control technique

Using the fracture mechanics parameters in assessment of integrity of rotary equipment

In this paper is presented the principle of application of fracture mechanics parameters in determining the integrity of rotary equipment. The behavior of rotary equipment depends on presence of cracks and basically determines the integrity and life of such equipment. The locations of stress concentration (i.e. radius changes) represent a particular problem in rotary equipment, and they are the most suitable places for the occurrence of microcracks i.e. cracks due to fatigue load. This problem is most common in the shaft of relatively large dimensions, for example, turbine shafts in hydropower plants made of high-strength carbon steel with relatively low fracture toughness, and relatively low resistance to crack formation and growth. Having in mind that rotary equipment represents the great risk in the exploitation, whose occasional failures often had severe consequences, it is necessary detail study of their integrity. For this purpose, it is necessary application of parameters of linear-elastic fracture mechanics, such as stress intensity factor, which range defines the rate of crack growth (Parisian law), and its critical value (fracture toughness) determines the critical crack length. The procedures for determining the critical crack length will be described using the fracture mechanics parameters

Mechanical behavior of fibrous root-inspired anchorage systems

Plant root-inspired geotechnics seeks to harness the principles of one of Earth’s most ubiquitous foundation elements to redesign or enhance conventional geotechnical infrastructure. In particular, the anchorage and material efficiency attributes of fibrous root systems are encapsulated in a novel root-inspired anchor that has the capability of surpassing conventional anchorage systems (e.g. tiebacks, tiedowns, plate and pile anchors) particularly in areas with weak soil or spatial constraints. The scope of this research fully exposes the application of the bio-inspired design process to the realization of root-inspired anchorage systems from 1) the reasoning behind the selection of fibrous root systems as a prime source of inspiration for sustainable, resilient anchor elements (e.g. plastic and thigmotropic adaptability properties, multifunctionality), to 2) the identification of the critical attributes of fibrous root systems to pullout behavior through testing of leek (Allium porrum) and spider (Chlorophytum comosum) plants, to 3) the design and fabrication of root-inspired anchor models, to 4) an extensive performance evaluation. More specifically, the root-inspired anchors are assessed in terms of their pullout behavior through a combination of analytical, experimental, and numerical analyses. The slip line method from plasticity theory is used as the basis to derive a solution for the prediction of plate anchor pullout capacity that was further modified to account for the more complex geometry of root-inspired anchors through mechanics-informed insights. Experimentally, a series of 1g pullout tests are performed to parametrically study the role of root-inspired anchor features (i.e. morphology, topology, material properties, and interface roughness) as well as soil properties (i.e. relative density, particle angularity, and particle size) on pullout behavior. Additionally, through a combination of x-ray CT imaging and digital image correlation (DIC), the formation and evolution of the soil failure surface during the uplift of a root-inspired anchor model is visualized and analyzed to connect the local soil kinematics to the global pullout response. With the finite volume method, the uplift process is simulated to validate experimental results and to extend the parametric study to a wider range of anchor and soil conditions. Finally a few considerations are highlighted concerning the upscale design, installation, and testing of these next generation anchor elements.Ph.D

SIMULATING SEISMIC WAVE PROPAGATION IN TWO-DIMENSIONAL MEDIA USING DISCONTINUOUS SPECTRAL ELEMENT METHODS

We introduce a discontinuous spectral element method for simulating seismic wave in 2- dimensional elastic media. The methods combine the flexibility of a discontinuous finite element method with the accuracy of a spectral method. The elastodynamic equations are discretized using high-degree of Lagrange interpolants and integration over an element is accomplished based upon the Gauss-Lobatto-Legendre integration rule. This combination of discretization and integration results in a diagonal mass matrix and the use of discontinuous finite element method makes the calculation can be done locally in each element. Thus, the algorithm is simplified drastically. We validated the results of one-dimensional problem by comparing them with finite-difference time-domain method and exact solution. The comparisons show excellent agreement