Mechanical Engineering Commons^™

Two And Three-Dimensional Isoparametric Finite Elements For Axisymmetric Micropolar Elasticity, Fuang-Yuan Huang

Dissertations

Finite element analysis program for isotropic and orthotropic axisymmetric micropolar (Cosserat) elastic solids are developed in this thesis. Isoparametric elements of 8- and 20- node are used to solve general three-dimensional problems, arid both 4- and 8-node elements are used for two-dimensional cases. Three-dimensional finite element formulation for cylindrical coordinate system is derived. Corresponding Fortran programs are then developed. Patch tests are performed for two-dimensional cases to verify the applicability of the finite element method to non-rectangular geometries. Several two-dimensional and three- dimensional problems for micropolar elastic solids are solved to verify the formulations arid computer program.

Good agreements were …

Deposition Of Suspensions In Convergent Channels Due To Electrostatic Image Forces, Kwok Wah Hui

Dissertations

The deposition of suspensions for uniform flow in convergent channels under the combined influences of inertia, viscous and electrostatic image forces was studied theorectically. The fluid phase was assumed to be two-dimensional, steady, uniform, incompressible and laminar while the particle phase was assumed to be uniform, steady, dilute and with negligible gravity effects.

Since the image force equations for convergent channels have not been derived, it becomes one of the main purposes of this study to perform the derivation of the image force equations. The lengths of the channels were chosen in a way that the exit area is only …

Deposition Of Particles In Tubes Due To Gravity And Electrostatic Charges, Win-Chung Chen

Dissertations

The deposition of particles in a parallel-plate channel and a circular tube under the influence of inertia, fluid viscosity, gravity and electrostatic image forces was studied by analytical and numerical methods. A laminar flow with uniform and parabolic velocity profiles was investigated with a particle initial velocity of zero as well as that of the local fluid velocity.

The governing equations were solved by the Lagrangian approach to obtain the particle trajectories from which the fraction of deposition was calculated. Closed form solutions for particle trajectory and a complete deposition of particles in a finite length of the flow passage …

Computer Aided Stress Analysis Of Long Bones Utilizing Computed Tomography, Shlomo Asher Marom

Dissertations

A computer aided analysis method, utilizing computed tomography (CT) has been developed, which together with a finite element program determines the stress-displacement pattern in a long bone section. The CT data file provides the geometry, the density and the material properties for the generated finite element model.

A three-dimensional finite element model of a tibial shaft is automatically generated from the CT file by a pre-processing procedure for a finite element program. The developed pre-processor includes an edge detection algorithm which determines the boundaries of the reconstructed cross-sectional images of the scanned bone. A mesh generation procedure then automatically generates …

An Analysis Of The Heating And Densification Process During Rotational Molding Of A Thermoplastic Powder In A Uniaxially Rotating Cylindrical Cavity, Floyd Steven Ribe

Dissertations

This dissertation presents the results of an experimental and theoretical investigation of the heating and densification portion of the rotational molding process in a uniaxial, cylindrical mold.

A thorough literature survey is included which reviewed past analysis of the rotational molding process and other areas that assisted in understanding of the process.

The results presented in this dissertation included an analysis of the densification process by use of Scanning Electronic Microscope (SEM) photography producing intermediate correlations between the physical properties of the densifying material and neck radius of adjacent coalescing spheres. In addition, a hybrid experimental procedure coupled with a …

Crimp-Type Electrical Connectors, Ted Lai-Che Kuo

Dissertations

Three types of surface conditions (plain surface, plain surface with oxidation inhibitor, and toothed surface) and four types of environmental gases (air, nitrogen, hydrogen, and oxygen) were used to study the performance of electrical connectors installed on aluminum conductors. All of the connectors were placed insealed vessels which allowed the desired type of gas to flow at a steady rate. The connectors were then current cycled.

For the connections prepared with plain surfaces, the connectors deteriorated equally fast in air, nitrogen and hydrogen. Only the connectorsexposed to oxygen showed a higher deterioration rate than the others.

Connections prepared withhaving plain …

Deposition Of Particles In Vertical Conduits Due To Electrostatic Charge, Diffusion, And Gravity, Melvin Wilbur Gelber

Dissertations

This investigation was made to determine the effect on the deposition of fine particles in a vertical channel and in a vertical tube due to the influences of electrostatic charge, diffusion, and gravity acting in the direction of flow. The flow considered was laminar, incompressible and steady.

The governing equations for the fluid phase were derived from the Navier-Stokes equation and the continuity equation while the equations for the particle phase were derived from Poisson's potential equation and the continuity equation. Since the governing equations are non-linear partial differential equations the solutions were developed using numerical methods.

The flow patterns …

Inplane And Out Of Plane Buckling Of Thick Rings Subjected To Hydrostatic Pressure, Thomas Michael Juliano

Dissertations

The problem of inplane and out of plane buckling of a thick circular ring subjected to a hydrostatic pressure is analyzed from first principals. The equations of equilibrium from nonlinear elasticity theory are used to describe two adjacent equilibrium positions, i.e., an initial and final state. The initial position problem is assumed to be governed by linear theory. The resulting incremental value equations obtained by subtracting the two equilibrium states, are also linear in nature. These problems are reduced to a one dimensional ring theory problem by the method of power series expansion of the displacements in the radial and …

Interaction Between Structures And Fluids, Rahim Falsafi-Haghighi

Dissertations

A finite element model for the study of solid-fluid interaction, with applications in flow-induced vibration analysis of reactor vessel and heat exchanger internals, is presented. The model is based on the discretization of the solid equation of motion and the fluid continuity and momentum equations and employs the solid displacements together with the fluid pressure and velocity components as the nodal degrees of freedom. This permits a realistic and accurate implementation of boundary conditions, in contrast with methods using solid displacements and fluid pressure as the only field variables. The numerical solution of the resulting matrix equation, involving non-symetric matrices, …

Dynamics Of Submerged Cylindrical Shells With Eccentric Stiffening, Kerry Kier-Ten Chu

Dissertations

A theoretical analysis is presented for treating the free vibrations of submerged, ring stiffened cylindrical shells with simply supported ends. The effects of the eccentric stiffeners are averaged over the thin-walled isotropic cylindrical shell. The energy method is utilized and the frequency equation is derived by Hamilton's Principle. All three degrees of freedom are considered. Numerical results are presented for frequencies and mode separation for several cases of interest. Comparisons with previous theoretical and experimental results indicate good agreement. The cylindrical wave approximation and the plane wave approximation for the field equation were investigated. Their applicability was evaluated and the …

Deposition Of Suspensions In Laminar Flow In The Entrance Region Of Channels With Diffusive, Electrostatic And Gravitational Effects, Thomas Anthony Korjack

Dissertations

This investigation entailed the consideration of the deposition of suspensions in laminar flow in the entrance region of a parallel-plate channel, and both converging and diverging channels, under the combined influences of diffusive, electrostatic and gravitational effects. The fluid phase was assumed to be incompressible, steady and laminar; the particle phase was assumed to be steady, laminar, dilute, and with negligible lift force.

The complete solution of the problem involved solving the boundary layer equations for the completely viscous fluid phase, and the particulate momentum, continuity and potential equations for the particle phase. Since the resulting equations are non-linear partial …

Axisymmetric Air Jet Impinging On A Hemispherical Concave Plate, Stefan Jachna

Dissertations

This experimental study was conducted on an axisymmetric air jet impinging normally on a smooth, hemispherical, concave plate. The jet Reynolds numbers, based on bulk nozzle velocity and nozzle exit air properties, were between 14,000 and 75,000.

The impingement plate used in this work was a hemispherical surface with the radius of 94 mm.

Calibrated Pitot tubes and a micromanometer were used for pressure and velocity measurements. The Pitot tubes were mounted on precision positioning mechanisms permitting the accurate traversing of any direction in space. The test air flow rate was measured with calibrated rotometers.

The following results of this …

A Fast Boundary Tracking Alogorithm For Constrained Nonlinear Mathematical Programming Problems, Jacob Yaghoub Moradi

Dissertations

A fast search algorithm for the solution of nonlinear mathematical programming optimization problems is presented in this thesis. A gradient search procedure is combined with a "Boundary Tracking"(BT) method using the feasible direction finding method of Zoutendijk for generating a feasible starting direction along the feasible-infeasible boundary.

The algorithm is applied to the minimum weight design of submersible, circular, cylindrical shells reinforced by equally spaced "T" type frames. This problem had produced algorithm failure in two earlier studies and was only recently solved by the Direct Search-Feasible Direction Algorithm (DSFD) which was shown by recent comparison studies to be among …

Dynamic Analysis Of Structures With Solid-Fluid Interaction, Rennee Ramona Pedrido

Dissertations

Interaction between solid and fluid has been recognized to be an important factor in the areas of aeroelasticity, hydroelasticity, and the study of flow-induced vibration in nuclear reactor components. This study develops a finite element model for interaction between an elastic solid and a fluid medium. Plane triangular finite elements have been used separately for fluid, solid, and solid-fluid continua and the equivalent mass, damping, and stiffness matrices and interaction load arrays for all elements are derived and assembled into global matrices. The global matrix differential equation of motion developed is solved in time to obtain the pressure and velocity …

Thermal Stratification And Circulation Of Water Bodies Subjected To Thermal Discharge, Mohammad A. Borhani

Dissertations

A three-dimensional analytical model for large water bodies is presented. Time histories and spatial distribution of pressure, velocity and temperature in water bodies, subjected to thermal discharge, are determined employing a digital computer. The dynamic response is obtained for a rectangular water body by applying a finite difference method to the mass, momentum and energy balance equations. These partial differential equations are algebraically manipulated to obtain; 1) three parabolic differential equations integrated temporally to find the horizontal velocity components and temperature; 2) one algebraic integral equation to get the vertical velocity component; 3) one elliptic differential equation integrated spatially to …

Deposition Of Suspensions In Laminar Flow In The Entrance Region Ofa Channel And In A Diffuser, Shawki Mahmoud Eldighidy

Dissertations

In this investigation, the deposition of suspensions in laminar flow in the entrance region of a channel and a diffuser was considered.

The particulate phase was considered to he under the action of the electric field force clue to electrostatic charges. In addition, a lift force acting on each particle at the wall arising from the fluid shear near the wall and an adhesive force between each particle and the wall due to the difference of the material properties for both particle and walls were considered as surface forces.

The suspension flow was assumed to be incompressible, laminar, dilute, and …

Design And Analysis Of An Instrument System For Rheological Testing Of Whole Blood Samples, Robert Rimvydas Sinusas

Dissertations

The dissertation covers the conceptual design of a rheometer for testing whole blood samples through to the clotting state. While the design aims at increased measurement accuracy, the design employs well known technologies and available components.

The main reason for preoccupation with blood testing is that recent investigations have indicated that physiological disorders can be correlated with rheological properties of blood. The pursuit of an improved means of correlation is initiated with a survey of the rheological properties of blood. The relevance of these blood properties is then discussed. From this discussion a broader blood model is developed as a …

Vibration And Buckling Of Elastic Plates With Shear And Rotatory Inertia, Bomi Batiwalla

Dissertations

The effects of shear, rotatory inertia and inplane forces on the transverse vibration of thin plates are studied. In addition, the effect of shear on the buckling of thin plates is examined. A general differential equation of motion is derived for an isotropic thin plate subjected to normal and inplane forces with the consideration of shear and rotatory inertia. The method of internal constraints and Hamilton's principle are utilized.

The resulting fourth order differential equation is solved for simply supported plates of various shapes by employing a finite difference technique. The shapes examined are a square, a circle, a circular …

The Effect Of Variable Properties On The Laminar Flow Of Gases, Norman Shilling

Dissertations

The problem of heat transfer in laminar flow of a gas through a constant diameter cylindrical tube is treated. The gas is cooled by the tube walls held at constant temperature. Two tube inlet conditions are considered: (1) fully developed velocity and uniform temperature profiles (Graetz boundary condition) and (2) uniform velocity and temperature (UTV) profiles. Results of the theoretical and experimental phases of the work are presented.

The theoretical solution is based on the compressible boundary layer equations with varying transport and thermodynamic property terms retained. For the Graetz condition, an existing finite difference solution scheme is modified for …

Transverse Vibration Of A Class Of Orthotropic Plates, Nicholas J. De Capua

Dissertations

This study determines the eigenvalues, eigenvectors, and nodal patterns of a class of orthotropic plates whose geometry is governed by the equation

(x/a)^α + (y/b)^β = 1,

where the parameters a, b, a, and a permit the plate geometry to vary over a range which includes the rhombus, circle, ellipse, square, and rectangle.

Variable thickness, inplane forces, and mixed or discontinuous boundary conditions are also considered. The following assumptions have been employed:

i). plate is thin with respect to other dimensions,

ii). deflections are small,

iii). rotary inertia and shear are neglected.

The method of analysis employed is …

A Theoretical And Experimental Study Of The Mechanism Of Axoplasmic Convection In Nerve Fibers Driven By Peristaltic Surface Waves, Robert John Biondi

Dissertations

In the study of cell biology, investigators have found that substances which are produced within the cell nucleus are sometimes found throughout the cell at points distant from the site of production. In the case of nerve cells (neurons), this is particularly dramatic because of the unusual elongated geometry of these cells.

A neuron possesses a cylindrical tubular extension called an "axon" or "axis cylinder" which is characterized by a large length-to-diameter ratio (10³-10⁶). The existence of a continuous proximo-distal flow of axoplasm within these cylindrical axons has now been demonstrated by numerous investigators. In …

Theoretical And Experimental Evaluation Of Cardiac State Utilizing Indicator Dilution Methods For Nonuniform Ventricular Mixing, Stanley Myron Welland

Dissertations

This research is directed toward the development and application of a new approach to the evaluation of cardiac work to diagnose cardiac state. A procedure has been developed for calculating the work performed on the fluid by the left ventricle during the heartbeat. The procedure involves the continuous direct measurement of ventricular fluid mixture temperature during and following the controlled injection, through a catheter, of a known volume of cold saline into the left ventricle. The measured mixture temperatures are used to calculate continuous ventricular volumes during the systolic and diastolic functions of the heartbeat. Plotting measured ventricular pressure versus …

On The Classification Of The Solution Space Of Linear Anisotropic Elasticity, Richard Clement Carman

Dissertations

A method is developed within the framework of Synge's function-space interpretation of problems in linear elasticity which allows the consideration of solutions to problems for anisotropic media in terms of the solutions of a corresponding isotropic problem and corresponding simpler anisotropic problems. The isotropic solution and simpler anisotropic solutions establish points in each of the statically and kinematically admissible spaces for the anisotropic problem. The established points are used to define sets of vectors in the statically and kinematically admissible spaces. The linear independence of these vectors can then be determined by a pair of criteria developed in this work. …

Non-Linear Analysis Of Electrocardiogram Tracings In Detection Of Occult Coronary Artery Disease, Joseph Robert Levitt

Dissertations

The general problem of identifying significant characteristics of a system by analyzing the properties of a signal emitted by that system is common to many disciplines, biological as well as physical. In general, achievement of a satisfactory solution depends on the capability of assigning membership of candidate signals to one of a number of mutually exclusive categories:

In this study, a new technique of processing the standard electrocardiograms from human subjects has been developed. This technique employs a set of non-linear transformations which enable the assignment of electrocardiograms into one of two Mutually exclusive categories. The first category is that …

Extension And Application Of The Sedov-Berdichevskii Variational Principle, Francis X. Prendergast

Dissertations

The Sedov-Berdichevskii variational principle is extended, and this extended principle is employed in the construction of a shell theory.

The extension of the principle is accomplished by the use of Lagrangian multipliers, and a redefinition of terms in order to maintain the original generality of the principle. The Euler equations of the extended variational principle provide, in addition to those obtained in the original principle, elastic and plastic kinematic relations, and, elastic and plastic constitutive relations. Also, the Euler equations of the original principle are obtained in a physically more meaningful form. Examples are given which show how this principle …

Dynamic Stress Concentrations About An Epilliptical Discontinuity In An Elastic Solid, Kenneth Roy Schroll

Dissertations

The redistribution of dynamic stresses caused by the presence of an elliptical discontinuity in an infinite isotropic homogeneous elastic solid is examined. The solutions are obtained for the special cases of the rigid immovable inclusion and the vacuous cavity inclusion, and numerical results are presented.

The solutions to the wave equations in elliptical coordinates are expressed in series of the elliptical geometry eigenfunctions. Application of the boundary conditions, vanishing displacements for the rigid immovable inclusion and vanishing stresses for the cavity inclusion, yields in each case two infinite sets of linear algebraic equations for the expansion coefficients of the series …