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This book is devoted to the Discrete Element Method (DEM) technique, a discontinuum modelling approach that takes into account the fact that granular materials are composed of discrete particles which interact with each other at the microscale level. This numerical simulation technique can be used both for dispersed systems in which the particle-particle interactions are collisional and compact systems of particles with multiple enduring contacts. The book provides an extensive and detailed explanation of the theoretical background of DEM. Contact mechanics theories for elastic, elastic-plastic, adhesive elastic and adhesive elastic-plastic particle-particle interactions are presented. Other contact force models are also discussed, including corrections to some of these models as described in the literature, and important areas of further research are identified. A key issue in DEM simulations is whether or not a code can reliably simulate the simplest of systems, namely the single particle oblique impact with a wall. This is discussed using the output obtained from the contact force models described earlier, which are compared for elastic and inelastic collisions. In addition, further insight is provided for the impact of adhesive particles. The author then moves on to provide the results of selected DEM applications to agglomerate impacts, fluidised beds and quasi-static deformation, demonstrating that the DEM technique can be used (i) to mimic experiments, (ii) explore parameter sweeps, including limiting values, or (iii) identify new, previously unknown, phenomena at the microscale. In the DEM applications the emphasis is on discovering new information that enhances our rational understanding of particle systems, which may be more significant than developing a new continuum model that encompasses all microstructural aspects, which would most likely prove too complicated for practical implementation. The book will be of interest to academic and industrial researchers working in particle technology/process engineering and geomechanics, both experimentalists and theoreticians.
This volume describes the application of the method of the differential specific forces (MDSF). By using this new method, the solutions to the problems of a dissipative viscoelastic and elastic-plastic contacts between curvilinear surfaces of two solid bodies can be found. The novelty is that the forces of viscosity and the forces of elasticity can be found by an integration of the differential specific forces acting inside an elementary volume of the contact zone. This volume shows that this method allows finding the viscoelastic forces for any theoretical or experimental dependencies between the distance of mutual approach of two curvilinear surfaces and the radiuses of the contact area. Also, the derivation of the integral equations of the viscoelastic forces has been given and the equations for the contact pressure have been obtained. The viscoelastic and elastic-plastic contacts at impact between two spherical bodies have been examined. The equations for work and energy in the phases of compression and restitution and at the rolling shear have been obtained. Approximate solutions for the differential equations of movement (displacement) by using the method of equivalent work have been calculated. This new method of differential specific viscoelastic forces allows us to find the equations for all viscoelastic forces. It is principally different from other methods that use Hertz’s theory, the classical theory of elasticity and the tensor algebra. This method will be useful in research of contact dynamics of any shape of contacting surfaces. It also can be used for determination of the dynamic mechanical properties of materials and in the design of wear-resistant elements and coverings for components of machines and equipment that are in harsh conditions where they are subjected to the action of flow or jet abrasive particles. This volume will be useful for professional designers of machines and mechanisms as well as for the design and development of new advanced materials, such as wear-resistant elastic coatings and elements for pneumatic and hydraulic systems, stop valves, fans, centrifugal pumps, injectors, valves, gate valves, and in other installations.
This book analyzes several compliant contact force models within the context of multibody dynamics, while also revisiting the main issues associated with fundamental contact mechanics. In particular, it presents various contact force models, from linear to nonlinear, from purely elastic to dissipative, and describes their parameters. Addressing the different numerical methods and algorithms for contact problems in multibody systems, the book describes the gross motion of multibody systems by using a two-dimensional formulation based on the absolute coordinates and employs different contact models to represent contact-impact events. Results for selected planar multibody mechanical systems are presented and utilized to discuss the main assumptions and procedures adopted throughout this work. The material provided here indicates that the prediction of the dynamic behavior of mechanical systems involving contact-impact strongly depends on the choice of contact force model. In short, the book provides a comprehensive resource for the multibody dynamics community and beyond on modeling contact forces and the dynamics of mechanical systems undergoing contact-impact events.
The volume introduces basic concepts necessary for a modern treatment of inequality problems in finite degree of freedom dynamics. Tools from convex analysis, by now well established in non-smooth mechanics, are used to formulate the constitutive equations and impact laws. The lectures cover a broad area of non-smooth dynamics from primal and dual energy functions in variational and differential form to application problems as chimney dampers or vibration conveyors. This includes frictional oscillations with bifurcation scenarios as well as analogies to small displacement quasi-static problems. The course is on an advanced level, designed primarily for postgraduate students, but should also be of value for scientists working on dynamic complementarity problems.
Open publication The volume deals with previously undescribed morphosyntactic variations and changes appearing in settings involving language contact. Contact-induced changes are defined as dynamic and multiple, involving internal change as well as historical and sociolinguistic factors. A variety of explanations are identified and their relationships are analyzed. Only a multifaceted methodology enables this fine-grained approach to contact-induced change. A range of methodologies are proposed, but the chapters generally have their roots in a typological perspective. The contributors recognize the precautionary principle: for example, they emphasize the difficulty of studying languages that have not been described adequately and for which diachronic data are not extensive or reliable. Three main perspectives on contact-induced language change are presented. The first explores the role of multilingual speakers in contact-induced language change, especially their spontaneous innovations in discourse. The second explores the differences between ordinary contact-induced change and change in endangered languages. The third discusses various aspects of the relationship between contact-induced change and internal change.
As mechanical systems become more complex so do the mathematical models and simulations used to describe the interactions of their parts. One area of multibody theory that has received a great deal of attention in recent years is the dynamics of multiple contact situations occurring in continuous joints and couplings. Despite the rapid gains in our understanding of what occurs when continuous joints and couplings interact, until now there were no books devoted exclusively to this intriguing phenomenon. Focusing on the concerns of practicing engineers, Multibody Dynamics with Unilateral Contacts presents all theoretical and applied aspects of this subject relevant to a practical understanding of multiple unilateral contact situations in multibody mechanical systems. In Part 1, Professor Pfeiffer and Dr. Glocker provide an exhaustive review of the laws and principles governing the dynamics of unilateral contacts in multibody mechanical and technical systems. Among the topics covered are multibody and contact kinematics, the dynamics of rigid body systems, multiple contact configurations, detachment and stick-slip transitions, frictionless impacts, impacts with friction, and the Corner law of contact dynamics. In Part 2, the authors present numerous applications of the theories presented in Part 1. Each chapter in this part is devoted to a different law, theory, or model, such as discontinuous force laws, classical impact theory, Coulomb's friction law, and mechanical and mathematical models of impacts and friction. In addition, each chapter features several practical examples that allow engineers to observe the concepts described in action. Examples are drawn from a broad array of fields and range from hammering in gears as occurring in a synchronous generator to impacts and friction as observed in a child's woodpecker toy, from a demonstration of classical impact theory using an automobile gear box example, to Coulomb's friction law as applied to a turbine blade damper. Multibody Dynamics with Unilateral Contacts is an indispensable resource for mechanical engineers working on all types of multibody systems and the friction and vibration problems that can occur in them. It is also a valuable reference for researchers studying nonlinear dynamics. The only book devoted entirely to the theory and applications of onE of the most crucial aspects of multibody system design. This is the first book to focus exclusively on the theory and applications of multiple contact situations occurring in continuous joints and couplings in multibody systems. As such, it is a valuable resource for engineers working on mechanical systems with interrelated multiple parts. Multibody Dynamics with Unilateral Contacts * Provides a comprehensive examination of the laws and principles governing the dynamics of unilateral contacts in multibody mechanical and technical systems. * Presents the latest mathematical models and simulation techniques for describing the interactions of joints and couplings in multibody systems. * Describes practical applications for all the concepts covered. * Includes numerous examples drawn from a wide range of fascinating and enlightening real-world demonstrations, including everything from an airplane's landing gear to a child's toy.
Discusses disparate findings to examine the dynamics of contact between languages in an immigrant context.
Research and theory on intergroup contact have become one of the fastest advancing and most exciting fields in social psychology in recent years. The work is exciting because it combines basic social psychological concerns -- human interaction, situational influences on behavior -- with an effective means of improving intergroup relations at a time when the world is witnessing widespread intergroup hatred and strife. This volume provides an overview of this rapidly progressing area of investigation – its origins and early work, its current status and recent developments, along with criticisms of this work and suggestions for future directions. It covers a range of research findings involving contact between groups drawn from the authors’ extensive meta-analysis of 515 published studies on intergroup contact. This meta-analysis, together with the authors’ renowned research on intergroup contact, provides a solid foundation and broad overview of the field, to which have been added discussions of research extensions and emerging directions. When Groups Meet is a rich, comprehensive overview of classic and contemporary work on intergroup contact, and provides insights into where this work is headed in the future. For research specialists, this volume not only serves as a sourcebook for research and theory on intergroup contact, it also provides the entire 515-item bibliography from the meta-analysis. The clear structure and accessible writing style will also appeal to advanced undergraduate and graduate students in psychology and other social sciences.
This textbook provides a comprehensive and instructive coverage of vehicular traffic flow dynamics and modeling. It makes this fascinating interdisciplinary topic, which to date was only documented in parts by specialized monographs, accessible to a broad readership. Numerous figures and problems with solutions help the reader to quickly understand and practice the presented concepts. This book is targeted at students of physics and traffic engineering and, more generally, also at students and professionals in computer science, mathematics, and interdisciplinary topics. It also offers material for project work in programming and simulation at college and university level. The main part, after presenting different categories of traffic data, is devoted to a mathematical description of the dynamics of traffic flow, covering macroscopic models which describe traffic in terms of density, as well as microscopic many-particle models in which each particle corresponds to a vehicle and its driver. Focus chapters on traffic instabilities and model calibration/validation present these topics in a novel and systematic way. Finally, the theoretical framework is shown at work in selected applications such as traffic-state and travel-time estimation, intelligent transportation systems, traffic operations management, and a detailed physics-based model for fuel consumption and emissions.
This carefully edited book offers a state-of-the-art overview on formulation, mathematical analysis and numerical solution procedures of contact problems. The contributions collected in this volume summarize the lectures presented by leading scientists in the area of contact mechanics, during the 4th Contact Mechanics International Symposium (CMIS) held in Hannover, Germany, 2005.