bluuebunny/crossref_metadata_2025 huggingface dataset:
Prospects of the Unification of Aerodynamics and Aeroacoustics
Authors: Branda˜o Mauri´cio Pazini
Published: April 2009

This paper reviews recent trends of analysis of aeroacoustic problems via traditional CFD techniques, as well as analysis of aerodynamic problems via modern aeroacoustic methods. Individual methods are described and tendencies of evolution are indicated. A generalized version of the full potential equation is derived. These two complementary forms of research converge towards the integration of Aeroacoustics and Aerodynamics into a single framework, where the computer serves as an integration tool.
Optimal Placement of Sensors to Detect Delamination in Composite Beams
Authors: Hajela P. , Teboub Y.
Published: April 2009

The paper describes an approach for the optimal placement of sensors in composite beam structures for online detection of damage. The ability to identify damage is based on establishing a mapping between the charactgeristics of specific damage mechanisms (location and extent) such as delamination, fiber breakage, and matrix cracking, and strain measurements at the selected sensor locations; a trained neural network is proposed as a tool to generate this mapping. The design problem considered in the present paper was to place the least number of sensors in the structure so that the ability of the neural network to predict the extent and location of damage is not compromised. The optimization problem involved a mix of discrete and integer variables, and a genetic algorithm was used as the search tool.
Some Aspects of Optimal Shaping of Cylindrical Shells Under Creep Conditions
Authors: Rysz M. , Serrano D. , Wroblewski A.
Published: April 2009

The present paper deals with structural optimal design of cylindrical shells under combined loading against creep rupture and creep buckling. Minimal weight of the shell is the design objective. Under the assumption of constant loading along the axis of the shell, the design objective reduces to the minimal cross-sectional area. Shape of the middle surface of the shell y(x) and the wall thickness h(x, y) are the functional variables. State equations are assumed in the form of nonlinear creep law for an incompressible body. The problem leads to variational optimization with respect to functional design variables under isoperimetric constraints for loading. The set of parameters satisfying a minimum of the cost function is then found numerically.
Simultaneous Structural and Control Optimization of Large Space Structures
Authors: Fonseca I. M. , Bainum P. M.
Published: April 2009

This paper focuses on the simultaneous structural/control optimization of a large space structure (LSS) subject to the gravity-gradient. The finite element method is used in conjunction with the Lagrangian formulation to derive the mathematical model for the structure. It is assumed to be a long unidimensional orbiting beam. In deriving the model vibrational and rotational planar motion and circular orbit are assumed. The NEWSUMT-A and the ORACLS computer programs are integrated to perform the simultaneous structural/control optimization problem. MATLAB software package is used for the transient phase simulation of the optimal integrated system. The simultaneous structural/control optimization is performed by the combined and the sequential integrated approaches (approach definitions are presented in this paper) with constraints on the structural weight, first natural frequency of vibration (bending), and on the damping (control). The results about the vibrational-rotational control for the optimal integrated system are presented through graphics. Comparison between those approaches shows some gains for the performance and control efforts for the sequential integrated approach.
Global Approximation of Response Surfaces and Application to Design Sensitivity Analysis
Authors: Jensen Hector A.
Published: April 2009

An approach based on global approximations to obtain response surfaces of structural systems is presented. The response surfaces are then used to evaluate the sensitivity of the system by considering the global behavior of the system response when the design parameters vary within a bounded region. The formulation of the method is based on the determination of approximated response surfaces, which are computed by minimizing a residual function over the design space. Different coefficients of sensitivity are introduced to measure the global variability of the system response. A numerical example is considered in order to show the usefulness of this technique. Great insight into the behavior of the system can be gained using this methodology. Finally, some extensions of the present work are presented.
Hyperelastic Materials Possessing Rotational Symmetry
Authors: Achcar Nelson
Published: April 2009

A representation theorem for the strain energy density function of a material possessing rotational symetry in a given direction (the weakest type of transverse isotropy) is presented. From this result, constitutive equations for hyperelastic unconstrained and incompressible materials that possess this kind of symmetry are derived.
Modeling of Turbulent Recirculating Flows Via an Iterative (k-L)-Predictor / (ε)-Corrector Scheme
Authors: Goldschmit M. B. , Cavaliere M. A.
Published: April 2009

A new iterative (k-L)-predictor / (ε)-corrector algorithm is used in the modeling of turbulent flows. The application of this model to recirculating flows is evaluated. The presented numerical results indicate that the developed iterative algorithm is very robust and does not require a case by case tuning.
Locking Behavior of Isoparametric Curved Beam Finite Elements
Authors: Bucalem Miguel Luiz , Bathe Klaus-Ju¨rgen
Published: April 2009

We present a study of the membrane and shear locking behavior in an isoparametric curved beam element. The objective is to gain insight into the locking phenomenon, specially membrane locking, of continuum based degenerated shell elements. This is possible since the isobeam element is the one-dimensional analogue of the continuum based shell element. In this context, reduced integration and mixed interpolation schemes are briefly examined. Such a study can be a valuable aid when developing new shell elements.
Key Response Features of Spherical Inflatables Under Axisymmetric Liquid Loading
Authors: Stanuszek Marek , Glockner Peter G.
Published: April 2009

Results on the large deflection and stability behavior of spherical inflatables subjected to axisymmetric hydrostatic loading are presented. Using an Eulerian description and assuming inextensibility, a set of integro-differential equations of the Volterra type defining the problem are solved numerically in the pond region. Using a numerical algorithm, the complete load-deflection behavior is determined for structures of different initial geometries and for various densities. Special attention is paid to γ = 9.0.
Nonlinear Elasticity Equations Referred to Anholonomic Coordinates
Authors: Altman Wolf , de Oliveira Antonio Marmo
Published: April 2009

This paper is concerned with properties of the anholonomic components of vectors and tensors. These properties give a tensorial character to the equations of motion when expressed in terms of those components and referred to a system of anholonomic coordinates. Examples of application of the theory are included.
Asymptotic-Numeric Solution for Shells of Revolution
Authors: Steele Charles R. , Shad Khaliq ur-Rehman
Published: April 2009

Thin shell structures offer a challenge to the analyst. It is well known that asymptotic expansion procedures offer simple approximate solutions for a number of shell problems for which direct numerical methods are inefficient. In this paper, a “very large finite element” method (VLFEM) is offered for the axisymmetric shell. The shape functions are obtained by sufficiently accurate asymptotic approximations through numerical procedures. A number of examples in statics and vibration have been considered that demonstrate the efficiency and accuracy of the approach.
Stiffness Constants for Composite Beams Including Large Initial Twist and Curvature Effects
Authors: Cesnik Carlos E. S. , Hodges Dewey H.
Published: April 2009

An asymptotically exact methodology, based on geometrically nonlinear, three-dimensional elasticity, is presented for cross-sectional analysis of initially curved and twisted, nonhomogeneous, anisotropic beams. Through accounting for all possible deformation in the three-dimensional representation, the analysis correctly accounts for the complex elastic coupling phenomena in anisotropic beams associated with shear deformation. The analysis is subject only to the restrictions that the strain is small relative to unity and that the maximum dimension of the cross section is small relative to the wave length of the deformation and to the minimum radius of curvature and/or twist. The resulting cross-sectional elastic constants exhibit second-order dependence on the initial curvature and twist. As is well known, the associated geometrically-exact, one-dimensional equilibrium and kinematical equations also depend on initial twist and curvature. The corrections to the stiffness model derived herein are also necessary in general for proper representation of initially curved and twisted beams.
Sensitivity Analysis and Conservation Law in Cracked Slab With Variable Thickness
Authors: Taroco Edgardo
Published: April 2009

Both shape sensitivity analysis and conservation law, concerning constant translation, are used to derive the J integral expression of elastic cracked slab with nonuniform thickness, submitted to the action of in-plane loading, applied body forces and prescribed tractions on its boundary. In this case J integral can be expressed as the sum of two integrals, one along an arbitrary contour around the crack tip and other over the domain surrounded by this contour. The domain integral involves the gradient of the thickness and the gradient of the body forces.
Convergence of the Ritz Method
Authors: Leissa Arthur W. , Shihada Samir M.
Published: April 2009

The Ritz method is widely used for the solution of problems in structural mechanics, especially eigenvalue problems where the free vibration frequencies or buckling loads are sought. It is well-known that the method yields upper bounds for these eigenvalues, and that convergence to exact eigenvalues will occur if proper admissible functions are used to represent the displacements (eigenfunctions). However, little is known about the convergence of the derivatives of the eigenfunctions. In this paper the method is studied for the problem of free vibrations of a cantilever beam. Convergences of the eigenfunctions and their second and third derivatives (i.e., bending moments and shear forces) are examined, as well as convergence to satisfy the differential equation of motion (which involves fourth derivatives). Another study examines the effects of deliberately omitting one term from the set of admissible displacement functions which would otherwise be complete. It is found that in such cases, when orthogonal polynomials are used to represent the displacement, one eigenvalue (such as the lowest frequency) may be completely missed, and that the others will converge incorrectly. When ordinary polynomials are used, correct convergence is obtained even with a missing term.
Interfacial Instabilities in Stratified Shear Flows Involving Multiple Viscous and Viscoelastic Fluids
Authors: Chen Kang Ping
Published: April 2009

This article reviews recent developments in the analysis of interfacial instabilities in systems involving multiple viscous and viscoelastic fluids. The scope of the review is limited to three basic problems in stratified shear flows: plane Poiseuille-Couette flow, circular Poiseuille flow, and gravity-driven film flow down an inclined plane. Important advances in this field of study are summarized and areas deserving further development are discussed.
Nonlinear Boltzmann Equation Solutions and Applications to Fluid Dynamics
Authors: Bellomo N. , LeTallec P. , Perthame B.
Published: April 2009

This paper provides a review of the mathematical results on the solution of the nonlinear Boltzmann equation. The survey deals both with analytical and computational aspects: Mathematical formulation of problems, initial and/or boundary value problems, a survey of the qualitative analysis of solutions, and computational treatment of fluid dynamical problems. A discussion of some problems deserving further study concludes this work.
Removal, Suppression, and Control of Chaos by Nonlinear Design
Authors: Lindner John F. , Ditto William L.
Published: April 2009

Techniques to remove, suppress, and control the chaotic behavior of nonlinear systems are reviewed. Analysis of a forced damped nonlinear oscillator provides a brief overview of the relevant nonlinear dynamics of dissipative systems. Various techniques for suppression and control of chaos are then outlined, compared and contrasted. A unified mathematical notation facilitates the comparison. The successes of each strategy in numerical simulations and physical experiments are carefully noted. Their strengths and weaknesses are analyzed, and they are evaluated according to whether they employ feedback, are goal-oriented, are model-based, merely remove chaos–or truly exploit it. An elementary derivation of the important OGY control equation is supplied. Critical references provide an entry into the literature. It is argued that nonlinearity can be a real-world advantage, and it is hoped that this review will serve as summary of, and invitation to, the nascent field of nonlinear design.
Random Vibration of Structures: A Personal Perspective
Authors: Elishakoff Isaac
Published: April 2009

Some topics in random vibration of structures are reviewed. For this occasion three topics are chosen: (a) effect of cross correlations in linear vibration of continuous structures, (b) effect of choice of deterministic theory describing the dynamic behavior of the structure, (c) new versions of stochastic linearization of nonlinear continuous structures. The essay attempts to partially answer a familiar but still nagging question “Now that I’m here, where am I?”
Ray Method for Solving Dynamic Problems Connected With Propagation of Wave Surfaces of Strong and Weak Discontinuities
Authors: Rossikhin Yuriy A. , Shitikova Marina V.
Published: April 2009

The aim of the article is to review the literature devoted to the solution of wave dynamics problems resulting in the propagation of nonstationary surfaces (volume waves) or lines (surface waves) of strong and weak discontinuities. In so doing one-term and multiple-term ray expansions, which are truncated power series with variable coefficients, are used. Jumps in all kinds of order of the time-derivatives of the functions to be desired serve as the coefficients. With their help the solutions are constructed behind the wave fronts up to the boundary of the wave motion domain. If the domains of the wave motion existence are extended, then the truncated ray series approximating the solution are not always uniformly valid over these domains. In this article, the methods for regularization of the truncated ray series are discussed, and in particular a new method which has been called by the authors as the method of “forward-area regularization”. These methods have gained recently wide application to solve the boundary-value problems connected with the wave propagation in bars, beams, plates, shells, 3D bodies, as well as with the dynamic contact interaction. In so doing, linear and nonlinear elastic, isotropic and anisotropic, thermoelastic, elastoplastic, and elastoviscoplastic media are used.
Layout Optimization of Structures
Authors: Rozvany G. I. N. , Bendso̸e M. P. , Kirsch U.
Published: April 2009

Layout or topology optimization deals with the selection of the best configuration for structural systems and constitutes one of the newest and most rapidly expanding fields of structural design, although some of its basic concepts were established almost a century ago. While mathematically and computationally perhaps the most challenging, it is also economically the most rewarding design task. This review article is based on a unified formulation and covers in detail both exact, analytical methods and approximate, discretized methods of layout optimization. Although discretized solutions are unavoidable for most practical, real-world problems, only explicit analytical solutions provide (i) a reliable means for checking the validity and convergence of numerical methods and (ii) a basis for assessing the relative economy of other designs. Moreover, some of the most efficient new numerical methods of layout optimization are iterative versions of analytical methods. Particularly promising are recent extensions of the exact layout theory to multiload, multipurpose elastic systems.
Numerical Simulations of Coherent Vortices in Turbulence
Authors: Lesieur Marcel , Comte Pierre , Me´tais Olivier
Published: April 2009

After presenting the general features of turbulent flows and coherent vortices, we discuss the major progress brought by Computational Fluid Dynamics (CFD) to the understanding of coherent vortices in turbulence. Afterwards, we present some simple vortex dynamics arguments allowing us to understand qualitatively the formation of coherent vortices during the transition to turbulence in shear flows. Of particular interest are the following elementary vortex interactions: roll up of a vortex sheet, pairing, dipole, even longitudinal hairpin, and odd longitudinal hairpin. Then direct numerical or large-eddy simulations of free-shear flows (mixing layers, backstep, jets, wakes), isotropic turbulence, and spatially-developing boundary-layers on a flat plate are presented. Following the editor’s request, these simulations focus mainly on the work done in France in Grenoble, which is however discussed within a broader numerical and experimental context. We show for instance that helical pairings may occur in plane mixing layers. The paper also presents in details the formalism of large-eddy simulations (LES) of turbulence, with the various models developed since Smagorinsky. We see for instance how longitudinal hairpin vortices are taken into account within these LES. Effects of compressibility upon turbulence are also considered: we study in particular mixing layers (where it is shown that helical pairing is inhibited above a certain convective Mach number), strongly heated boundary layers at low Mach number, and supersonic compression ramps within the frame of the HERMES European space-shuttle reentry project. Finally, we look at the influence of solid-body rotation on incompressible turbulence. In the case of a free-shear layer, we study shear/Coriolis linear instability, which, in anticyclonic conditions and at moderate rotation rates, yields a purely longitudinal mode. Numerical simulations show how this mode evolves non-linearly into concentrated longitudinal hairpin vortices of absolute vorticity. We also consider the case of initially isotropic turbulence subject to rotation.
Material Forces: Concepts and Applications
Authors: Maugin Ge´rard A.
Published: April 2009

The unifying notion of material force which gathers under one vision all types of driving “forces” on defects and smooth or abrupt inhomogeneities in fracture, defect mechanics, elastodynamics (localized solutions) and allied theories such as in electroelasticity, magnetoelasticity, and the propagation of phase transition fronts, is reviewed together with its many faceted applications. The presentation clearly distinguishes between the role played by local physical balance laws in the solution of boundary-value problems and that played by global material balance laws in obtaining the expression of relevant material forces and devising criteria of progress for defects, in a general way. The advances made along this line, which may be referred to as Eshelbian mechanics, are assessed and perpectives are drawn.
Anisotropic Symmetries of Linear Elasticity
Authors: Cowin S. C. , Mehrabadi M. M.
Published: April 2009

The objective of this paper is to present a development of the anisotropic symmetries of linear elasticity theory based on the use of a single symmetry element, the plane of mirror symmetry. In this presentation the thirteen distinct planes of mirror symmetry are catalogued. Traditional presentations of the anisotropic elastic symmetries involve all the crystallographic symmetry elements which include the center of symmetry, the n-fold rotation axis and the n-fold inversion axis as well as the plane of mirror symmetry. It is shown that the crystal system symmetry groups, as opposed to the crystal class symmetry groups, of the elastic crystallographic symmetries can be generated by the appropriate combinations of the orthogonal transformations corresponding to each of the thirteen distinct planes of mirror symmetry. It is also shown that the restrictions on the elastic coefficients appearing in Hooke’s law follow in a simple and straightforward fashion from orthogonal transformations based on a small subset of the small catalogue of planes of mirror symmetry.
Some Basic Thermoelastic Problems for Nonhomogeneous Structural Materials
Authors: Tanigawa Yoshinobu
Published: April 2009

The focus of this review is on the method of analytical development of thermoelastic problems for nonhomogeneous materials, such as functionally gradient materials (FGM). For such nonhomogeneous materials, both the thermal and mechanical material constants are described by the function of the variable of the coordinate system. Then, the governing equations for the temperature field and the associated thermoelastic field become of nonlinear form in general cases. Therefore, the theoretical treatment is very difficult and the exact solution for the temperature and the thermoelastic field is almost impossible to obtain. This nonlinear equation system is usually treated by introducing some linearization technique with appropriate theoretical approximation. In this review, the method of some analytical developments for the heat conduction problem and the associated thermal stress problem of a body with nonhomogeneous material properties is explained briefly, and some boundary value problems of technical interest, such as optimization problems for material nonhomogeneity and the problems of thermal stress intensity factor for a body with a crack, are discussed.
Simple Models of Human Movement
Authors: Alexander R. McN.
Published: April 2009

Many mathematical models of human movement have sought to represent as much as possible of the complexity of the human body but others, the subjects of this review, are extremely simple. Some treat the body as a point mass walking on rigid, massless legs or bouncing along on a spring. Others incorporate a few limb segments with appropriate masses, operated in some cases by a few muscles with realistic physiological properties. These simple models have been used to tackle questions such as these: why do we walk at low speeds but break into a run to go faster? Why do we change the length of our strides, and the patterns of force we exert on the ground, as we increase speed? Why do high jumpers run up more slowly than long jumpers and set down the take-off leg at a shallower angle? Why do we activate muscles sequentially, when throwing a ball? In every case the explanatory power of the model is enhanced by its simplicity.
Suspended Sediment Concentration Profiles
Authors: Nielsen Peter
Published: April 2009

An evaluation is given of the methods of modeling concentration profiles of suspended non-cohesive sediments in natural streams and under waves. The bottom boundary condition and the distribution models are treated separately. The merits of the simple concentration boundary condition, which has been favored by practice, are compared to those of the more general pickup function approach. Experimental evidence is presented for the inadequacy of pure gradient diffusion as a framework for modeling sediment suspension in streams and under waves. But problems arise when a significant part of the upward sediment flux is carried by vortices through distances comparable with the overall vertical scale. The performance of an alternative distribution model is discussed.
Coastal Bottom Boundary Layers
Authors: Sleath J. F. A.
Published: April 2009

Turbulent boundary layers in oscillatory flow are reviewed. These boundary layers show a thin inner layer with similar characteristics to wall layers in steady flow. Above this, there is an outer layer which has some characteristics which are the same as those of steady flow outer layers and other characteristics which are different. One difference is that the defect velocity profile does not scale on the shear velocity alone. Also, over rough beds, the turbulence intensity in the outer layer falls off with height in a similar way to oscillating grid turbulence. Transition from laminar to turbulent flow is also reviewed. Combined oscillatory and steady flows are only briefly touched on.
Solidification of Pure Liquids and Liquid Mixtures Inside Ducts and Over External Bodies
Authors: Fukusako Shoichiro , Yamada Masahiko
Published: April 2009

Recent advances in the understanding of transport phenomena during solidification inside ducts and over external bodies are discussed. The emphasis is on fundamental aspects of the phenomena observed in transport processes during solidification. After a discussion of the solidification of pure substances, transport processes during solidification of binary systems are reviewed. The important role played by fluid motion owing to density gradients is also discussed and future research needs are assessed.
Bifurcation and Stability in Dissipative Media (Plasticity, Friction, Fracture)
Authors: Nguyen Quoc Son
Published: April 2009

This paper addresses stability and bifurcation analysis for common systems of solids in the framework of plasticity, of friction and of fracture mechanics. Although physically different, usual time-independent laws adopted in these domains lead to a certain mathematical similarity concerning the quasi-static behaviour of materials and structures. These mechanical systems can be described practically in the same mathematical manner concerning their quasi-static evolution and in particular concerning the stability of their response. Our objective is to present within this framework a review of principal results of the recent literature on these subjects in relation with some energy-related considerations and with an unified description based upon energy and dissipation analysis.
Analytical, Computational and Experimental Investigations on Stress Wave Propagation
Authors: Ho¨schl C. , Okrouhli´k M. , Cˇerv J. , Benesˇ J.
Published: April 2009

Wave phenomena in intensely loaded bodies are often paradoxical and unexpected. They are evoked by stress wave interactions and depend substantially on actual material properties, body shapes and dimensions, friction, etc. Their proper understanding is indispensable for the reliable evaluation of the quality of various technologies as nuclear reactor safety, armour penetration, nondestructive testing, etc. The paper presents a survey of analytical, computational and experimental techniques and methods being employed for the solutions of stress wave propagation problems in solids.
Solid Layer Thermal-Conductivity Measurement Techniques
Authors: Goodson K. E. , Flik M. I.
Published: April 2009

The thermal conductivities of solid layers of thicknesses from 0.01 to 100 μm affect the performance and reliability of electronic circuits, laser systems, and microfabricated sensors. This work reviews techniques that measure the effective thermal conductivity along and normal to these layers. Recent measurements using microfabricated experimental structures show the importance of measuring the conductivities of layers that closely resemble those in the application. Several promising non-contact techniques use laser light for heating and infrared detectors for temperature measurements. For transparent layers these methods require optical coatings whose impact on the measurements has not been determined. There is a need for uncertainty analysis in many cases, particularly for those techniques which apply to very thin layers or to layers with very high conductivities.
Piezoelectricity and Its Use in Disturbance Sensing and Control of Flexible Structures: A Survey
Authors: Rao S. S. , Sunar M.
Published: April 2009

Piezoelectric materials are being used at an increasing rate by researchers in the areas of vibration, measurement and control. Due to their distinct features, these materials can be employed in the distributed sensing and control of intelligent structures that have a highly integrated control architecture. By employing piezoelectric materials, it is feasible to achieve an accurate response monitoring and effective control of flexible structures. In this survey paper, the recent research trends addressing piezoelectricity in the context of distributed sensing and control of flexible structures are discussed. A brief history of piezoelectricity is also noted.
Simulations of Plastic Instabilities in Solid Mechanics
Authors: Tomita Yoshihiro
Published: April 2009

The purpose of the present article is provide a perspective for computational predictions related to such plastic instabilities as buckling, necking and flow localization including shear–banding under a wide range of deformation rates for a variety of materials, including single– and polycrystals. Computational bifurcation analyses for general cases, axisymmetric to nonaxisymmetric deformation, very thin–walled bodies, and specific materials with nonstandard constitutive equations are given. The postbifurcation analyses and regularization schemes to remedy the problems associated with spurious mesh sensitivity and incorrect convergence in finite element prediction of flow localization behavior are discussed. The instability behavior of thick circular tubes deformed under pressure and combined loading of internal/external pressure and axial force, neck and bulge propagations in polymeric materials, wrinkling of thin plates and shells under sheet metal forming processes, flow localization of thermo–elasto–viscoplastic materials under a wide range of deformation rates including adiabatic shear banding, and flow localization behavior of mono– and polycrystalline solids are reviewed with illustrative examples.
Friction-Induced Vibration, Chatter, Squeal, and Chaos—Part I: Mechanics of Contact and Friction
Authors: Ibrahim R. A.
Published: April 2009

Friction force between sliding surfaces arises due to varied and complex mechanisms and can be responsible for undesirable dynamic characteristics in many mechanical systems. Controversies over the theory of friction have been reported in the literature. Friction laws are phenomenological in charcacter since they are based on observable and measurable quantities. The mechanics of contact and friction in metal-metal and elastomer-metal contact surfaces are reviewed. Unfortunately, there is no satisfactory method capable of determining or measuring the area of contact between sliding bodies. Both dry friction and lubricated friction are considered. The modeling of the friction force in mechanical systems depends on several factors. These include the material properties and geometry of the sliding surfaces, surface roughness, surface chemistry, sliding speed, temperature, and normal load. Other factors include the effect of normal and tangential vibrations on the static friction. Here the static friction is considered as a special case of kinetic friction. This background is essential for dynamicists studying friction-induced vibration, chatter, squeal and chaos topics which will be presented in the second part.
Friction-Induced Vibration, Chatter, Squeal, and Chaos—Part II: Dynamics and Modeling
Authors: Ibrahim R. A.
Published: April 2009

This part provides a comprehensive account of the main theorems and mechanisms developed in the literature concerning friction-induced noise and vibration. Some of these mechanisms are based on experimental investigations for classical models. Bilinear and nonlinear dynamical models have been considered to explain such friction phenomena as stick-slip, chatter, squeal, and chaos. Nonlinear modeling includes two types of nonlinearities which differ from those encountered in structural dynamics. These nonlinearities, in addition to the observed uncertainty of friction between sliding surfaces, form a formidable difficulty in developing accurate and reliable modeling. They include the inherent nonlinearity of contact forces (eg, Hertzian contact), and the nonlinear relationship between friction and sliding relative velocity. Research activities in this area are a mixture of theoretical, numerical, and experimental investigations. Theoretical investigations are prevailed by deterministic analysis with few attempts of stochastic treatment. The models include classical and practical engineering models such as the mass-spring model sliding on a running belt or on a surface with Hertzian contact, a pin sliding on a rotating disk, beams with friction boundaries, turbine blades, water-lubricated bearings, wheel-rail systems, disc brake systems and machine cutting tools. There is a strong need for further research to promote our understanding of the various friction mechanisms and to provide designers of sliding components with better guidelines to minimize the deteriorating effects of friction.
Reynolds Number Effects in Wall-Bounded Turbulent Flows
Authors: Gad-el-Hak Mohamed , Bandyopadhyay Promode R.
Published: April 2009

This paper reviews the state of the art of Reynolds number effects in wall-bounded shear-flow turbulence, with particular emphasis on the canonical zero-pressure-gradient boundary layer and two-dimensional channel flow problems. The Reynolds numbers encountered in many practical situations are typically orders of magnitude higher than those studied computationally or even experimentally. High-Reynolds number research facilities are expensive to build and operate and the few existing are heavily scheduled with mostly developmental work. For wind tunnels, additional complications due to compressibility effects are introduced at high speeds. Full computational simulation of high-Reynolds number flows is beyond the reach of current capabilities. Understanding of turbulence and modeling will continue to play vital roles in the computation of high-Reynolds number practical flows using the Reynolds-averaged Navier-Stokes equations. Since the existing knowledge base, accumulated mostly through physical as well as numerical experiments, is skewed towards the low Reynolds numbers, the key question in such high-Reynolds number modeling as well as in devising novel flow control strategies is: what are the Reynolds number effects on the mean and statistical turbulence quantities and on the organized motions? Since the mean flow review of Coles (1962), the coherent structures, in low-Reynolds number wall-bounded flows, have been reviewed several times. However, the Reynolds number effects on the higher-order statistical turbulence quantities and on the coherent structures have not been reviewed thus far, and there are some unresolved aspects of the effects on even the mean flow at very high Reynolds numbers. Furthermore, a considerable volume of experimental and full-simulation data have been accumulated since 1962. The present article aims at further assimilation of those data, pointing to obvious gaps in the present state of knowledge and highlighting the misunderstood as well as the ill-understood aspects of Reynolds number effects.
Heat and Fluid Flow Inside Rotating Channels
Authors: Yang Wen-Jei , Fann Shin , Kim John H.
Published: April 2009

Power generation and refrigeration accomplished by means of rotating or reciprocating machinery. One of the basic elements of rotating machinery is the rotating channel system. With the desire for ever increasing efficiency in power generation and refrigeration, higher or lower operating temperatures are achieved. It has provided motivation for the pursuit of knowledge on heat transfer and fluid flow characteristics. This paper reviews the literature pertinent to studies of fluid flow and/or heat transfer in channel flows subjected to radial rotation, parallel rotation, and coaxial revolution. Special problems unique to rotating systems are discussed and future study areas are suggested.
Review of Microscale Heat Transfer
Authors: Duncan A. B. , Peterson G. P.
Published: April 2009

A review of the literature in the area of microscale heat transfer is presented to provide a concise overview of the recent advances in this field of study. The review is divided into three major sections with each subdivided into subsections. The first section deals with the effects of size reductions in conduction heat transfer, and includes subsections on laser induced heating on the microscale and conduction in thin films. The second section addresses microscale forced convection and includes subsections on micro heat pipes, microscale boiling, and thin liquid films near the contact line. The final section examines the effects of small length scales on radiative heat transfer. The three major sections are followed by a summary that identifies, consolidates, and summarizes the most important advances in each of these three areas.
Nonlinear Random Vibration: Experimental Results
Authors: Ibrahim R. A.
Published: April 2009

Experimental investigations of random excitation of dynamic systems are valuable but scarce. They are particularly important for nonlinear random vibrations, since different approaches can lead to different results for the same problem. They are also useful in providing physical insight into a number of complex dynamic phenomena and in identifying the modal parameters of systems. The scarcity of random vibration testing is mainly due to a number of difficulties and errors encountered in generating the correct random excitation, and data acquisition. The purpose of this review article is to assess the recent experimental results reported in the literature by the author and others. An attempt will be made to correlate the experimental measurements qualitatively with those predicted analytically. In most cases, no quantitative comparisons have been made. Difficulties encountered in experimental tests, data acquisition, and associated errors, will be discussed. New research directions based on recent analytical and experimental developments in the theory of nonlinear random vibration will also be outlined.
Application of the Finite Element Method to Linear Elastic Fracture Mechanics
Authors: Banks-Sills Leslie
Published: April 2009

Use of the finite element method to treat two and three-dimensional linear elastic fracture mechanics problems is becoming common place. In general, the behavior of the displacement field in ordinary elements is at most quadratic or cubic, so that the stress field is at most linear or quadratic. On the other hand, the stresses in the neighborhood of a crack tip in a linear elastic material have been shown to be square root singular. Hence, the problem begins by properly modeling the stresses in the region adjacent to the crack tip with finite elements. To this end, quarter-point, singular, isoparametric elements may be employed; these will be discussed in detail. After that difficulty has been overcome, the stress intensity factor must be extracted from either the stress or displacement field or by an energy based method. Three methods are described here: displacement extrapolation, the stiffness derivative and the area and volume J-integrals. Special attention will be given to the virtual crack extension which is employed by the latter two methods. A methodology for calculating stress intensity factors in two and three-dimensional bodies will be recommended.
Structural and Dynamic Behavior of Pretwisted Rods and Beams
Authors: Rosen Aviv
Published: April 2009

Because of being important structural elements in many engineering applications on one hand, and presenting inherent complicated coupling effects on the other hand, pretwisted rods have attracted the interest of many researchers. During the years, as a result of engineering breakthroughs, like the introduction of composite materials or operating at very high temperatures, the problems associated with pretwisted rods became more complicated. The present review will present the research during the last fifty years. It will be divided into three main subjects: static analysis, dynamic analysis and stability problems. The review will concentrate on the structural and dynamic aspects of pretwisted rods. Derivations of models and solution techniques will be addressed.
Multibody Dynamics — Modeling and Analysis Methods
Authors: Huston R. L.
Published: April 2009

A review of recent developments in multibody dynamics modeling and analysis is presented. Multibody dynamics is one of the fastest growing fields of applied mechanics. Multibody systems are increasingly being employed as models of physical systems such as robots, mechanisms, chains, cables, space structures, and biodynamic systems. Research activity in multibody dynamics has stimulated research in a number of subfields including formulation methods, system modeling, numerical procedures, and graphical representations. These are also discussed and reviewed.
Structure of Mixing Layers and Jets
Authors: Thomas F. O.
Published: April 2009

This article is intended as a brief review of the substantial progress that has been made in recent years regarding our understanding of the structure of incompressible mixing layers and jets. The work has been aimed at the graduate student who possesses a familiarity with the general areas of laminar-turbulent transition and turbulence, but is not familiar with the specific research areas involving mixing layer and jet flows. The article should be of assistance both in assimilating the vast body of literature that exists in this field as well as in deciding what avenues present fertile grounds for investigation. Since a number of the topics described are relatively new, it is believed that the article will also be of interest to the specialist. The review should not be considered exhaustive but rather should serve to guide the interested reader to more detailed works.
Heat Transfer in Superconducting Films
Authors: Flik M. I.
Published: April 2009

Thin films that are superconducting above liquid-nitrogen temperature possess promising applications in electronics and sensor technology. The design, the characterization and the processing of devices based on the high-temperature superconductors pose new fundamental heat transfer problems. This article reviews thermal conduction, thermal radiation and thermal stability phenomena in superconducting films. The understanding of these thermal phenomena requires solid-state physics and materials science, in addition to heat transfer and thermodynamics. Future research opportunities are pointed out for thermal problems in superconducting films.
Nonlinear Dynamic Response of Membranes: State of the Art
Authors: Jenkins Chris H. , Leonard John W.
Published: April 2009

Membrane structures have been used since the earliest of times. Until recently, their analysis has relied chiefly on trial and error; however, modern methods of analysis are evolving. The deformations are nearly always of the large rotation and/or strain type and are thus inherently nonlinear. Static analysis can be considered as a special case of the dynamic analysis. This paper is concerned then with reviewing methods of nonlinear dynamic analysis of membrane structures. Two problems of analysis are associated with membrane structures: (i) shape (or form) finding; (ii) response (deformation and/or stress) analysis. Shape finding (ie, determination of the surface geometry given an initial prestress, generation of cutting patterns, etc) is nontrivial but well documented in the literature and is not considered in this paper. In this review attention is instead focused on formulation of field equations, wrinkling analysis, fluid/structure interactions, material nonlinearities, and computational methods.
Topology of Flow Separation on Three-Dimensional Bodies
Authors: Chapman Gary T. , Yates Leslie A.
Published: April 2009

In recent years there has been extensive research on three-dimensional flow separation. There are two different approaches: the phenomenological approach and a mathematical approach using topology. These two approaches are reviewed briefly and the shortcomings of some of the past works are discussed. A comprehensive approach applicable to incompressible and compressible steady-state flows as well as incompressible unsteady flow is then presented. The approach is similar to earlier topological approaches to separation but is more complete and in some cases adds more emphasis to certain points than in the past. To assist in the classification of various types of flow, nomenclature is introduced to describe the skin-friction portraits on the surface. This method of classification is then demonstrated on several categories of flow to illustrate particular points as well as the diversity of flow separation. The categories include attached, two-dimensional separation and three different types of simple, three-dimensional primary separation, secondary separation, and compound separation. Hypothetical experiments are utilized to illustrate the topological terminology and its role in characterizing these flows. These hypothetical experiments use colored oil injected onto the surface at singular points in the skin-friction portrait. Actual flow-visualization information, if available, is used to corroborate the hypothetical examples.
Thermally Induced Flexure, Buckling, and Vibration of Plates
Authors: Tauchert Theodore R.
Published: April 2009

A survey is made of investigations concerned with the response of flat plates to thermal loadings. The discussion focuses on three major topics: (i) thermally induced bending, (ii) buckling, postbuckling, and large deformation behaviors, and (iii) vibrational characteristics associated with elevated temperatures and rapid heating. Consideration is given both to thin and to moderately thick plates, plates having various planforms and support conditions, and isotropic homogeneous, as well as anisotropic or heterogeneous material behaviors. In addition, references are cited to works dealing with the response of variable thickness plates, plates resting on elastic foundations, inelastic response, and optimal thermoelastic design.
Thermomechanical Coupling in Inelastic Solids
Authors: Allen David H.
Published: April 2009

Coupling between mechanical and thermodynamic processes can be significant in solid media when material inelasticity occurs. Significant mechanical energy may be converted into heat via hysteretic loss, and this coupling may be significant even under quasi-static conditions. Important advances have been made since the second world war in modeling this thermomechanical coupling. This paper reviews many of the major achievements on this subject. The paper opens with a short review of historical milestones on the subject. A theoretical model is then reviewed, including both conservation laws and constitutive models for certain classes of solids. The paper concludes with a discussion of recent attempts to solve the inelastic coupled thermomechanical field problem.
Thermal Stresses in Materials with Temperature-Dependent Properties
Authors: Noda Naotake
Published: April 2009

The present review on thermal stresses in materials with temperature-dependent properties focuses on papers published after 1980. The thermal and mechanical properties in materials subjected to thermal loads due to high temperature, high gradient temperature, and cyclical changes of temperature are dependent on temperature. The main theme of the thermoelastic problems in materials and structures with temperature-dependent material properties is to establish analytical procedures to solve the governing differential equations. In the thermo-inelastic problems, however, we must perform more accurate analysis of the practical problems (weld, heat treatment, metal forming, etc) taking account of the temperature-dependent material properties by use of numerical procedures (finite element methods, mainly).