Showing papers in "Applied Mechanics Reviews in 2003"

Historical review of Zig-Zag theories for multilayered plates and shells

Abstract: This paper gives a historical review of the theories that have been developed for the analysis of multilayered structures. Attention has been restricted to the so-called Zig-Zag theories, which describe a piecewise continuous displacement field in the plate thickness direction and fulfill interlaminar continuity of transverse stresses at each layer interface. Basically, plate and shell geometries are addressed, even though beams are also considered in some cases. Models in which the number of displacement variables is kept independent of the number of constitutive layers are discussed to the greatest extent. Attention has been restricted to those plate and shell theories which are based on the so-called method of hypotheses or axiomatic approach in which assumptions are introduced for displacements and/or transverse stresses. Mostly, the work published in the English language is reviewed. However, an account of a few articles originally written in Russian is also given. The historical review conducted has led to the following main conclusions. 1! Lekhnitskii ~1935! was the first to propose a Zig-Zag theory, which was obtained by solving an elasticity problem involving a layered beam. 2! Two other different and independent Zig-Zag theories have been singled out. One was developed by Ambartsumian ~1958!, who extended the well-known Reissner-Mindlin theory to layered, anisotropic plates and shells; the other approach was introduced by Reissner ~1984!, who proposed a variational theorem that permits both displacements and transverse stress assumptions. 3 ! On the basis of historical considerations, which are detailed in the paper, it is proposed to refer to these three theories by using the following three names: Lekhnitskii Multilayered Theory, ~LMT!, Ambartsumian Multilayered Theory ~AMT!, and Reissner Multilayered Theory ~RMT!. As far as subsequent contributions to these three theories are concerned, it can be remarked that: 4! LMT although very promising, has almost been ignored in the open literature. 5! Dozens of papers have instead been presented which consist of direct applications or particular cases of the original AMT. The contents of the original works have very often been ignored, not recognized, or not mentioned in the large number of articles that were published in journals written in the English language. Such historical unfairness is detailed in Section 3.2. 6! RMT seems to be the most natural and powerful method to analyze multilayered structures. Compared to other theories, the RMT approach has allowed from the beginning development of models which retain the fundamental effect related to transverse normal stresses and strains. This review article cites 138 references. @DOI: 10.1115/1.1557614#

Mechanics of composite structures

Abstract: Preface List of symbols 1. Introduction 2. Displacements, strains, stresses 3. Laminated composites 4. Thin plates 5. Sandwich plates 6. Beams 7. Beams with shear deformation 8. Shells 9. Finite element analysis 10. Failure criteria 11. Micromechanics Appendix A. Cross-sectional properties of thin-walled composite beams Appendix B. Buckling loads and natural frequencies of orthotropic beams with shear deformation Appendix C. Typical material properties Index.

Verification, Validation, and Predictive Capability in Computational Engineering and Physics

Abstract: Developers of computer codes, analysts who use the codes, and decision makers who rely on the results of the analyses face a critical question: How should confidence in modeling and simulation be critically assessed? Verification and validation (V&V) of computational simulations are the primary methods for building and quantifying this confidence. Briefly, verification is the assessment of the accuracy of the solution to a computational model. Validation is the assessment of the accuracy of a computational simulation by comparison with experimental data. In verification, the relationship of the simulation to the real world is not an issue. In validation, the relationship between computation and the real world, i.e., experimental data, is the issue.

Perspectives in Flow Control and Optimization

Abstract: From the Publisher: Flow control and optimization has been an important part of experimental flow science throughout the last century. As research in computational fluid dynamics (CFD) matured, CFD codes were routinely used for the simulation of fluid flows. Subsequently, mathematicians and engineers began examining the use of CFD algorithms and codes for optimization and control problems for fluid flows. The marriage of mature CFD methodologies with state-of-the-art optimization methods has become the center of activity in computational flow control and optimization. Perspectives in Flow Control and Optimization presents flow control and optimization as a subdiscipline of computational mathematics and computational engineering. It introduces the development and analysis of several approaches for solving flow control and optimization problems through the use of modern CFD and optimization methods. The author discusses many of the issues that arise in the practical implementation of algorithms for flow control and optimization, such as choices to be made and difficulties to overcome. He provides the reader with a clear idea of what types of flow control and optimization problems can be solved, how to develop effective algorithms for solving such problems, and potential problems to be aware of when implementing the algorithms. This book is written for both those new to the field of control and optimization as well as experienced practitioners, including engineers, applied mathematicians, and scientists interested in computational methods for flow control and optimization. Both those interested in developing new algorithms and those interested in the application of existing algorithms should find useful information in this book. Readers with a solid background in calculus and only slight familiarity with partial differential equations should find the book easy to understand. Knowledge of fluid mechanics, computational fluid dynamics, calculus of variations, control theory or optimization is beneficial, but is not essential, to comprehend the bulk of the presentation. Only Chapter 6 requires a substantially higher level of mathematical knowledge, most notably in the areas of functional analysis, numerical analysis, and partial differential equations. Fortunately, this chapter is completely independent of the others so that, even if this chapter is not well understood, the majority of the book should still prove useful and informative. About the Author Max D. Gunzburger is a Distinguished Professor in the Department of Mathematics at Iowa State University and also Francis Eppes Professor in the School for Computational Science and Information Technology and the Department of Mathematics at Florida State University. An active member of both AMS and SIAM, he is Editor-in-Chief of the SIAM Journal on Numerical Analysis and Associate Editor of the SIAM Journal on Control and Optimization. He also serves on the editorial boards of the SIAM Advances in Design and Control book series and the International Journal for Computational Fluid Dynamics.

Immersed boundary technique for turbulent flow simulations

Abstract: The application of the Immersed Boundary ~IB! method to simulate incompressible, turbulent flows around complex configurations is illustrated; the IB is based on the use of non-body conformal grids, and the effect of the presence of a body in the flow is accounted for by modifying the governing equations. Turbulence is modeled using standard Reynolds-Averaged Navier-Stokes models or the more sophisticated Large Eddy Simulation approach. The main features of the IB technique are described with emphasis on the treatment of boundary conditions at an immersed surface. Examples of flows around a cylinder, in a wavy channel, inside a stirred tank and a piston/cylinder assembly, and around a road vehicle are presented. Comparison with experimental data shows the accuracy of the present technique. This review article cites 70 references. @DOI: 10.1115/1.1563627# 1 CONTEXT The continuous growth of computer power strongly encourages engineers to rely on computational fluid dynamics ~CFD! for the design and testing of new technological solutions. Numerical simulations allow the analysis of complex phenomena without resorting to expensive prototypes and difficult experimental measurements. The basic procedure to perform numerical simulation of fluid flows requires a discretization step in which the continuous governing equations and the domain of interest are transformed into a discrete set of algebraic relations valid in a finite number of locations ~computational grid nodes! inside the domain. Afterwards, a numerical procedure is invoked to solve the obtained linear or nonlinear system to produce the local solution to the original equations. This process is simple and very accurate when the grid nodes are distributed uniformly ~Cartesian mesh! in the domain, but becomes computationally intensive for disordered ~unstructured! point distributions. For simple computational domains ~a box, for example! the generation of the computational grid is trivial; the simulation of a flow around a realistic configuration ~a road vehicle in a wind tunnel, for example!, on the other hand, is extremely complicated and time consuming since the shape of the domain must include the wetted surface of the geometry of interest. The first difficulty arises from the necessity to build a smooth surface mesh on the boundaries of the domain ~body conforming grid!. Usually industrially relevant geometries are defined in a CAD environment and must be translated and cleaned ~small details are usually eliminated, overlapping surface patches are trimmed, etc! before a surface grid can be generated. This mesh serves as a starting point to generate the volume grid in the computational domain. In addition, in many industrial applications, geometrical complexity is combined with moving boundaries and high Reynolds numbers. This requires regeneration or deformation of the grid during the simulation and turbulence modeling, leading to a considerable increase of the computational difficulties. As a result, engineering flow simulations have large computational overhead and low accuracy owing to a large number of operations per node and high storage requirements in combination with low order dissipative spatial discretization. Given the finite memory and speed of computers, these simulations are very expensive and time consuming with computational meshes that are generally limited to around one million nodes. In view of these difficulties, it is clear that an alternative numerical procedure that can handle the geometric complexity, but at the same time retains the accuracy and high efficiency of the simulations performed on regular grids, would represent a significant advance in the application of CFD to industrial flows.

Computational strategies for flexible multibody systems

Abstract: The status and some recent developments in computational modeling of flexible multibody systems are summarized. Discussion focuses on a number of aspects of flexible multibody dynamics including: modeling of the flexible components, constraint modeling, solution techniques, control strategies, coupled problems, design, and experimental studies. The characteristics of the three types of reference frames used in modeling flexible multibody systems, namely, floating frame, corotational frame, and inertial frame, are compared. Future directions of research are identified. These include new applications such as micro- and nano-mechanical systems; techniques and strategies for increasing the fidelity and computational efficiency of the models; and tools that can improve the design process of flexible multibody systems. This review article cites 877 references. @DOI: 10.1115/1.1590354#

Passive Vibration Isolation

Abstract: Description: Production equipment for microelectronics, MEMS, and nanotechnology cannot function without vibration isolation. Process plant, power generation machinery, oil, gas, and petrochemical equipment are all subject to vibration. This vibration causes a range of problems and headaches for the engineer that can lead to failure of equipment, downtime, and extra maintenance costs. Isolating vibration and ameliorating it is vital. This valuable and well–written text provides a comprehensive treatment of the principles of design and means for realization of passive vibration isolation systems for real–life objects. A special emphasis is given to effective techniques and methods that are not yet widely used in the practice of vibration isolation in industry. It is written with practitioners in mind and many of the problems addressed and the solutions presented are relevant not only to the isolation of stationary sensitive equipment but also to civil engineering and transport applications. CONTENTS INCLUDE Inertia and geometric properties of typical machines and other mechanical devices Dynamics of single–degreeof–freedom vibration isolation system Vibration isolation system under random excitation Isolation of vibration–sensitive objects Vibration isolation systems; Isolation requirements for vibration producing objects Engine and machinery mounting in vehicles Elasto–damping materials (EDM) High damping metals Material selection for vibration isolators Vibration isolators with metal flexible elements High angular stiffness and anisotropic vibration isolation systems Pneumatic isolators Power transmission couplings

Nanomechanics of carbon nanotubes and composites

Abstract: Computer simulation and modeling results for the nanomechanics of carbon nanotubes and carbon nanotube-polyethylene composite materials are described and compared with experimental observations Young’s modulus of individual single-wall nanotubes is found to be in the range of 1 TPa within the elastic limit At room temperature and experimentally realizable strain rates, the tubes typically yield at about 5–10% axial strain; bending and torsional stiffness and different mechanisms of plastic yielding of individual single-wall nanotubes are discussed in detail For nanotube-polyethylene composites, we find that thermal expansion and diffusion coefficients increase significantly, over their bulk polyethylene values, above glass transition temperature, and Young’s modulus of the composite is found to increase through van der Waals interaction This review article cites 54 references @DOI: 101115/11538625#

Turbulent flow : analysis, measurement, and prediction

Abstract: Preface. Acknowledgments. 1. Preliminaries. 2. Overview of Turbulent Flow Physics and Equations. 3. Experimental and Numerical Methods. 4. Properties of Bounded Turbulent Flows. 5. Properties of Turbulent Free Shear Flows. 6. Turbulent Transport. 7. Theory of Idealized Turbulent Flows. 8. Turbulence Modeling. 9. Applications of Turbulence Modeling. 10. Large Eddy Simulations. 11. Analysis of Turbulent Scalar Fields. 12. Turbulence Theory. Author Index. Subject Index.

Radiation Heat Transfer: A Statistical Approach

Abstract: Preface. Acknowledgments. FUNDAMENTALS OF THERMAL RADIATION. Introduction to Thermal Radiation. Basic Concepts the Blackbody. Description of Real Surfaces Surface Properties. Radiation Behavior of Surfaces. Wave Phenomena in Thermal Radiation. Radiation in a Participating Medium. TRADITIONAL METHODS OF RADIATION HEAT TRANSFER ANALYSIS. Solution of the Equation of Radiative Transfer. The Net Exchange Formulation for Diffuse, Gray Enclosures. Evaluation of Configuration Factors. Radiative Analysis of Nondiffuse, Nongray Surfaces Using the Net Exchange Formulation. THE MONTE CARLO RAY-TRACE (MCRT) METHOD. Introduction to the Monte Carlo Ray-Trace (MCRT) Method. The MCRT Method for Diffuse-Specular, Gray Enclosures: An Extended Example. The Distribution Factor for Nondiffuse, Nongray, Surface-to-Surface Radiation. The MCRT Method Applied to Radiation in a Participating Medium. Statistical Estimation of Uncertainty in the MCRT Method. Appendix A: Radiation from an Atomic Dipole. Appendix B: Mie Scattering by Homogeneous Spherical Particles: Program UNO. Appendix C: A Functional Environment for Longwave Infrared Exchange (FELIX). Appendix D: Random Number Generators and Autoregression Analysis. Index.

Flow Control by Feedback: Stabilization and Mixing

Abstract: 1 Introduction.- 2 Governing Equations.- 3 Control Theoretic Preliminaries.- 4 Stabilization.- 5 Mixing.- 6 Sensors and Actuators.- A Coefficients for the Ginzburg-Landau Equation.

Analysis and Design of Elastic Beams: Computational Methods

Abstract: Beams in Bending. Beam Elements. Beam Systems. Finite Elements for Cross-Sectional Analysis. Saint-Venant Torsion. Beams Under Transverse Shear Loads. Restrained Warping of Beams. Analysis of Stress. Rational B-Spline Curves. Shape Optimization of Thin-Walled Sections. Appendix A: Using the Computer Programs. Appendix B: Numerical Examples.

Geodynamics of the Lithosphere: An Introduction

Abstract: Plate Tectonics- Energetics: Heat and Temperature- Kinematics: Morphology and Deformation- Mechanics: Force and Rheology- Dynamic Processes- Metamorphic Processes

Boundary Element Method, Volume 1: Applications in Thermo-Fluids and Acoustics

Abstract: This two-volume book set is designed to provide the readers with acomprehensive and up-to-date account of the boundary element methodand its application to solving engineering problems. Each volume isa self-contained book including a substantial amount of materialnot previously covered by other text books on the subject. Volume 1covers applications to heat transfer, acoustics, electrochemistryand fluid mechanics problems, while volume 2 concentrates on solidsand structures, describing applications to elasticity, plasticity,elastodynamics, fracture mechanics and contact analysis. The earlychapters are designed as a teaching text for final yearundergraduate courses. Both volumes reflect the experience of theauthors over a period of more than twenty years of boundary element research.