Showing papers in "Journal of Applied Mechanics in 1984"

A Simple Higher-Order Theory for Laminated Composite Plates

Abstract: A higher-order shear deformation theory of laminated composite plates is developed. The theory contains the same dependent unknowns as in the first-order shear deformation theory of Whitney and Pagano (1970), but accounts for parabolic distribution of the transverse shear strains through the thickness of the plate. Exact closed-form solutions of symmetric cross-ply laminates are obtained and the results are compared with three-dimensional elasticity solutions and first-order shear deformation theory solutions. The present theory predicts the deflections and stresses more accurately when compared to the first-order theory.

Applications of Fractional Calculus to the Theory of Viscoelasticity

Abstract: Relation entre le calcul fractionnaire et la theorie de l'equation integrale d'Abel pour les materiaux a memoire. On obtient les fonctions de fluage et de relaxation en termes de fonction de Mittag-Leffler qui depend de la derivee fractionnaire du parametre β (parametre de memoire)

On the Appearance of the Fractional Derivative in the Behavior of Real Materials

Abstract: On propose des relations constitutives generalisees pour les materiaux viscoelastiques dans lesquelles les derivees d'ordre entier par rapport au temps sont remplacees par des derivees d'ordre fractionnaire. De tels modeles decrivent bien le comportement des materiaux reels

Probabilistic Methods in the Theory of Structures

Abstract: Keywords: probabilites ; structures ; vibration ; methodes de : calcul Reference Record created on 2005-11-18, modified on 2016-08-08

On the Propagation of Bulges and Buckles

Abstract: On decrit deux exemples de propagation de modes d'instabilite dans des conditions quasi-statiques et quasi-stationnaires: 1) gonflement d'un ballon a partie cylindrique dans lequel un renflement se propage dans le sens de la longueur; 2) affaissement d'un tube sous effet d'une pression externe par suite du flambage. Dans chacun de ces exemples il existe une barriere importante a l'initiation du mode d'instabilite. Existence d'une pression critique

Computer Aided Analysis and Optimization of Mechanical System Dynamics

Abstract: These proceedings contain lectures presented at the NATO-NSF-ARO sponsored Advanced Study I stitute on "Computer Aided Analysis and Optimization of Mechanical System Dynamics" held in Iowa City, Iowa, 1-12 August, 1983. Lectures were presented by free world leaders in the field of machine dynamics and optimization. Participants in the Institute were specialists from throughout NATO, many of whom presented contributed papers during the Institute and all of whom participated actively in discussions on technical aspects of the subject. The proceedings are organized into five parts, each addressing a technical aspect of the field of computational methods in dynamic analysis and design of mechanical systems. The introductory paper presented first in the text outlines some of the numerous technical considerations that must be given to organizing effective and efficient computational methods and computer codes to serve engineers in dynamic analysis and design of mechanical systems. Two substantially different approaches to the field are identified in this introduction and are given attention throughout the text. The first and most classical approach uses a minimal set of Lagrangian generalized coordinates to formulate equations of motion with a small number of constraints. The second method uses a maximal set of cartesian coordinates and leads to a large number of differential and algebraic constraint equations of rather simple form. These fundamentally different approaches and associated methods of symbolic computation, numerical integration, and use of computer graphics are addressed throughout the proceedings.

High Shear Stresses in Stiff-Fiber Composites

Abstract: L'analyse elastique de 2 fibres paralleles dans une matrice infinie soumise a un cisaillement longitudinal, conduit a des resultats exacts pour les concentrations de contraintes entre les fibres. Des contraintes de cisaillement elevees se produisent lorsque des fibres raides sont tres proches

Dynamics of Constrained Multibody Systems

Abstract: Etude des equations de mouvement de systemes a n corps soumis a des contraintes soit geometriques (boucles fermees), soit cinematiques (mouvement specifique)

The Elastic Inclusion With a Sliding Interface

Abstract: Lorsqu'une inclusion ellipsoidale subit une deformation propre de cisaillement et que l'inclusion est libre de glisser le long de l'interface, le champ de contrainte tend vers zero en tout point de l'inclusion et de la matrice

Dynamics of Gyroelastic Continua

Abstract: On introduit l'idee de gyricite distribuee selon laquelle chaque element de volume d'un milieu continu possede une quantite infinitesimale de moment angulaire stocke. Le milieu continu est suppose elastique. On etablit une equation aux derivees partielles regissant les petits deplacements de ce milieu continu gyroelastique. On deduit les modes de vibration gyroelastique

Friction, Restitution, and Energy Loss in Planar Collisions

Abstract: Both particle and rigid body planar collisions are covered in this paper. For particles, the classical equations for oblique impacts are derived using Newton’s laws along with definitions of the coefficient of restitution and equivalent coefficient of friction. A general expression is obtained for the kinetic energy loss explicity containing the two coefficients. This expression for energy loss as a function of the friction coefficient possesses a maximum. The value of the friction coefficient at the maximum is a limiting value which can be used to determine whether or not sliding exists at separation. The maximum energy loss is independent of the physical mechanism of generation of tangential forces (friction) and serves as an upper bound for two-particle collisions. It is shown that to properly formulate and solve the rigid body problem, a moment must be considered at the common “point” of impact. A moment coefficient of restitution must be defined. This leads to six linear algebraic equations from which the six final velocity components can be calculated. An analytical solution is obtained for the general rigid body problem. In a reduced form, it is used to solve the problem of a single rigid body impacting a rigid barrier. This solution is then applied to a classical textbook problem. As shown for particle impacts, the concepts of limiting friction coefficient and maximum energy loss apply to rigid body impacts.

Thermoelastic Displacements and Stresses Due to a Heat Source Moving Over the Surface of a Half Plane

Abstract: If two thermally conducting bodies are in sliding contact, the frictional heat generated at the interfaces causes thermoelastic distortion which profoundly influences the extent of the contact area and the distribution of contact stress [1]. This phenomenon now known as thermoelastic instability has been observed experimentally in a wide range of practical sliding systems [2, 3]. Several theoretical solutions have been obtained to problems of this kind, e.g., [4-6], but most make the assumption that one of the bodies is either rigid or a nonconductor or both, thus ensuring that the temperature field is stationary in the deformable solid. In the more general problem, the contact area and hence the temperature field will move with respect to both solids. One way to treat problems of this kind is to use the Green's function for a moving heat source on the surface of the body. The two-dimensional Green's function for a heat source moving over the surface of an elastic half plane was first investigated by Ling and Mow [7], who used Fourier transformation to obtain a simplified solution in which conduction of heat in the direction of motion is neglected. This approximation is justified at large Peclet number i.e., when

Eigenvalues and Stable Time Steps for the Uniform Strain Hexahedron and Quadrilateral

Abstract: On obtient des formules simples pour limiter les valeurs limites maximums ou pour les calculer exactement pour les elements de deformation hexaedrique a 8 nœuds et en quadrilatere a 4 nœuds. L'analyse de valeurs propres est limitee aux materiaux lineaires isotropes

Bifurcation Theory Applied to Oil Whirl in Plain Cylindrical Journal Bearings

Abstract: THeorie des bifurcations appliquee au fouettage de l'huile dans des paliers cylindriques simples

Endochronic Theory of Cyclic Plasticity With Applications

Abstract: Etude de la plastification d'un acier doux soumis a une charge cyclique. Modele mathematique et verification experimentale

On the Numerical Implementation of Elastoplastic Models

Abstract: On donne une solution fermee pour l'evolution des contraintes au cours d'une etape elastoplastique dans des conditions de durcissement ou d'adoucissement purement cinematique. Lorsqu'on inclut des effets isotropes l'analyse devient plus difficile et on developpe alors une solution de perturbation. Comparaison avec des algorithmes d'elements finis

The Energy-Release Rate in the Growth of a One-Dimensional Delamination

Abstract: Utilisation de la methode de l'integrale J pour obtenir une expression algebrique du taux de liberation d'energie en termes de la solution de postflambage de la plaque delaminee

A Hybrid/Finite Element Approach for Stress Analysis of Notched Anisotropic Materials

Abstract: Calcul des contraintes ou des facteurs d'intensite des contraintes a des entailles, coupures ou autres discontinuites geometriques dans des materiaux anisotropes charges dans le plan

Fully Plastic Crack Problems, Part 1: Solutions by a Penalty Method

Abstract: Elaboration d'un modele pregnant, aux elements finis integres, applicable a la description et la comprehension, des phenomenes se produisant dans des materiaux incompressibles

Influence of Geometric Imperfections and In-Plane Constraints on Nonlinear Vibrations of Simply Supported Cylindrical Panels

Abstract: This papers deals with the effects of initial geometric imperfections on large-amplitude vibrations of cylindrical panels simply supported along all four edges. In-plane movable and in-plane immovable boundary conditions are considered for each pair of parallel edges. Depending on whether the number of axial and circumferential half waves are odd or even, the presence of geometric imperfections (taken to be of the same shape as the vibration mode) of the order of the shell thickness may significantly raise or lower the linear vibration frequencies. In general, an increase (decrease) in the linear vibration frequency corresponds to a more pronounced soft-spring (hard-spring) behavior in nonlinear vibration.

Fracture Mechanics of Concrete: Material Characterization and Testing

Abstract: 1. Mechanics of material damage in concrete.- 1.1 Introduction.- 1.2 Mechanical strength of concrete.- 1.3 Stress and fracture analysis.- 1.4 Damage analysis of concrete beam in bending: effects of softening and loading step.- 1.5 Scaling of specimen size.- 1.6 Long time behavior and failure of concrete.- 1.7 Local and global stationary values of strain energy density function.- 1.8 General discussion.- References.- 2. Evaluation of concrete fracture.- 2.1 Introduction.- 2.2 Mechanism of failure in concrete.- 2.3 Behaviour of concrete under loading related to damage.- 2.4 Mechanical modeling of concrete by means of fracture mechanics.- References.- 3. Fracture toughness testing of cement and concrete.- 3.1 Introduction.- 3.2 Physical phenomena involved in fracture.- 3.3 Rate of loading effects.- 3.4 Notch sensitivity.- 3.5 Historical review of the applications of fracture mechanics to cementitious materials.- 3.6 Fracture toughness parameters and techniques.- 3.7 Valid specimen size.- 3.8 Conclusions.- References.- 4. Dependence of concrete fracture toughness on specimen geometry and on composition.- 4.1 Introduction.- 4.2 Resistance curves.- 4.3 Theoretical model.- 4.4 Uniaxial tensile stress-displacement relationship.- 4.5 Experimental investigation.- 4.6 Comparison with experimental data.- 4.7 Effects of compositions.- References.- 5. Microcracking in concrete.- 5.1 Introduction.- 5.2 Microcracking of concrete.- 5.3 Methods of study of microcracking.- 5.4 Effects of microcracks on the properties of concrete.- 5.5 Cracking of higher-strength versus lower-strength concrete.- 5.6 Summary.- References.- 6. Interferometry in scattered coherent light applied to the analysis of cracking in concrete.- 6.1 Introduction.- 6.2 The suitability of interferometric methods in scattered coherent light in the analysis of concrete cracking.- 6.3 Significance and quality of fringes obtained with interferometry in scattered coherent light.- 6.4 Comparative summary.- 6.5 Application of interferometric methods in scattered coherent light to the analysis of concrete cracking.- 6.6 Conclusion.- References.- Author index.

Measuring Techniques in Gas-Liquid Two-Phase Flows

Abstract: Optical Imaging.- Holographic Measurements of Bubble Size and Velocity in a Three-Phase System.- Drop Size Measurement in a Vertical Gas-Liquid Flow.- A Comparative Study Between Holographic and Light-Scattering Techniques of Microbubble Detection.- High-Speed Multiple Spark Cameras for Gas-Liquid Tow-Phase Flow Studies.- Flow Visualization in Two-Phase Flow.- The Measurement of Liquid Phase Velocity Profiles in Vertical Two-Phase Flow.- Optical Scattering.- Development and Application of a Two-Colour Particle Sizing Instrument.- Turbulence Measurements in Two-Phase Bubbly Flows Using Laser-Doppler Anemometry.- Simultaneous Measurement of Size and Two-Velocity Components of Large Droplets in a Two-Phase Flow by Laser-Doppler Anemometry.- Application of an Optical Scatterer to the Study of Two-Phase Flow in Vertical Pipes.- Raman Scattering in Two-Phase Flows with Application to Temperature Measurements.- Optical and Acoustical Attenuation.- Optimization of an Experimental Setup for Void Fraction Determination by the X-Ray Attenuation Technique.- LOBI Spectrum-Stabilized Gamma Densitometers.- Measurement of Transient Flow Pattern by High Speed Scanning X-Ray Void Fraction Meter.- A Single-Beam Multi-Detector Gamma Densitometer for Void Fraction and Phase Distribution Measurements in Transient Two-Phase Flows.- Measurement of Noncondensible Distribution of Two-Phase Flow Experiments Using Ultraviolet Attenuation Techniques.- Void Fraction Measurement by an Ultrasonic Transmission Technique in Bubbly Gas-Liquid Two-Phase Flow.- Neutron Physics.- Neutronic Fluctuation Analysis as a Characterizing Vehicle for Two-Phase Flow.- Design Aspects of a Fast Neutron Scattering Technique for Phase Distribution Measurement in Two-Phase Flow.- Tagging Technique.- Theory of the Determination of Slip Ratio in High Pressure Steam-Water Flows Using an 16N Tagging Technique.- Two-Phase Flow Measurement Using a Pulsed-Photon-Activation (PPA) Technique.- A Nuclear Magnetic Resonance Method for the Investigation of Two-Phase Flow.- Local Probes, Technology and Signal Analysis.- Velocity, Measurement with Electrical Couble-Sensing Devices in Two-Phase Flow.- Ultrasonic Doppler Measurements of Bubble Velocities in Bubble Columns.- Real-Time Measurement of Two-Phase Flow Turbulence Using a Dual-Sensor Anemometry.- An Overall-Void Sensor and an Optical Measuring Device.- Two-Phase Flow Identification by Calibration with Stochastic Parameters.- Flowmeters.- Orifice Plates: Two-Phase Applications.- Residual Error Problems in True Mass Flowmeters.- Two-Phase Mass Flow Rate Measurements with Pitot Tubes and Density Measurements.- Vertical Liquid-Liquid and Liquid-Gas Two-Phase Flow Measurements with a Vortex Flowmeter.- Test of Two-Phase Mass Flow Rate Instrumentation in Transient Steam-Water Flow.- Electrochemical Method.- Electrochemical Method for Measuring Turbulent Characteristics of Gas-Liquid Flows.- Wall Shear Measurements by Electrochemical Probes in Two-Phase Flow. Bubble and Slug Regimes.- Analytical Index.

Nonlinear Vibration of Thin Elastic Plates, Part 1: Generalized Incremental Hamilton’s Principle and Element Formulation

Abstract: The finite element method has been widely used for analyzing nonlinear problems, but it is surprising that so far only a few papers have been devoted to nonlinear periodic structural vibrations. In Part 1 of this paper, a generalized incremental Hamilton’s principle for nonlinear periodic vibrations of thin elastic plates is presented. This principle is particularly suitable for the formulation of finite elements and finite strips in geometrically nonlinear plate problems due to the fact that the nonlinear parts of inplane stress resultants are functions subject to variation and that the Kirchhoff assumption is included as part of its Euler equations. Following a general formulation method given in this paper, a simple triangular incremental modified Discrete Kirchhoff Theory (DKT) plate element with 15 stretching and bending nodal displacements is derived. The accuracy of this element is demonstrated via some typical examples of nonlinear bending and frequency response of free vibrations. Comparisons with previous results are also made. In Part 2 of this paper, this incremental element is applied to the computation of complicated frequency responses of plates with existence of internal resonance and very interesting seminumerical results are obtained.