Digital Commons Network^™

A Finite Element For The Three-Dimensional Deformation Of A Circular Ring Of Arbitrary Cross Section, Jeffrey Stuart Knowlton

Mechanical Engineering ETDs

A two-node finite element for relatively compact, solid curved beams is derived. A node is located at the centroid of each end of the beam, and each node has six degrees of freedom, consisting of three translations and three rotations in mutually perpendicular directions. The element stiffness matrix has dimensions 12x12. A cylindrical polar coordinate system is used to express the components of the associated displacement and load vectors. As a consequence of the assumption of a nonzero cross-section product of inertia, deflec­tions in the plane and out of the plane of beam curvature are coupled. Hence in-plane loads can …

Use Of Thermal Storage For Load Management In A Solar-Augmented Heat Pump System, James Thomas Schmitz

Mechanical Engineering ETDs

Electric utilities are today faced with the dilemma of satisfying increasing demands for electrical energy while their ability to build new power plants is being severely curtailed primarily due to environmental concerns. By redistributing the power demand of individual customers (and thus the utility) with respect to time, greater overall electricity consumption can be met without increasing the generating capacity of the utility. This redistribution can be accomplished using thermal energy storage at the customer’s location. For heating and cooling of buildings, thermal storage, combined with off-peak period operation of the mechanical system's major electricity consuming equipment, can lower peak …

The Compatibility Of Mild Carbon Steel And Water In A Heat Pipe Application, David D. Kenney

Mechanical Engineering ETDs

The phenomena that govern the performance and affect the lifetime of heat pipes are reviewed. The phenomena include the corrosion of metals by aqueous solutions, the diffusion of gases through metals, and the effects of hydrogen on metals. Heat pipes of 1015 C.D. carbon steel were fabricated and operated with a control group of 304 stainless steel heat pipes over the temperature range from 140° to 300° C. Results indicate that carbon steel/water heat pipes perform as well or better than 304 stainless steel/water heat pipes over the temperature range covered in this test.

Lee's Moment Method Applied To Binary Flow In Jet And Channel Devices Used For The Aerodynamic Separation Of Uranium Isotopes, Edward Eugene Holcomb

Mechanical Engineering ETDs

Lees' moment method is applied to the problem of compressible, binary flow of uranium hexafluoride gas through a parallel plate chan­nel. The time-dependent numerical problem is solved to yield the steady state solution. The results obtained are preliminary to the solution of the flow field for the curved nozzle and colliding jet devices used in the aerodynamic separation of uranium isotopes. Lees' concept of two-sidedness of the distribution function doubles the number of variables required to describe the system, and the resulting set of moment equations is not easily solved. The assumptions of isothermal, hydrodynamically fully developed flow are made …

A Survey Of Structural Identification Techniques, Doris Evelyn Miller

Mechanical Engineering ETDs

This work is a collection and survey of system identification methods in the open literature. The motivation for the work was to find suitable methods of system identification for use in structural diagnosis. Methods surveyed include those which identify the system in terms of modal parameters, and those which identify the system either nonparametrically or in terms of arbitrary parameters. Both deterministic and stochastic methods are reviewed. Particular emphasis is placed on determining damping coefficients, and on a formulation known as modal synthesis. It is concluded that stochastic methods are better suited to the problem of structural diagnosis, and that …

Geothermal Energy: Heat Extraction From Hot-Dry-Rock Masses In The Presence Of Secondary Thermal Cracks, Yaw-Min Lu

Mechanical Engineering ETDs

Additional heat extraction from geothermal energy reservoirs depends on the feasibility to extend the main, hydraulic fracture through secondary thermal cracks of the adjacent hot rock. When the main, hydraulic fracture is cooled sufficiently, these secon­dary thermal cracks are produced normal to the main fracture surface, As such, both the heat transfer surface area and heat energy available to the fluid circulating through the main, hydraulic fracture system increase.

A Design Study For A Wavy Hydrodynamic Mechanical Face Seal, Raymond Edward Pierce

Mechanical Engineering ETDs

A desirable objective of mechanical face seal design is to achieve the maximum hydrodynamic load support possible while main­taining an acceptable leakage. In this way, mechanical face seal life can be greatly extended as the wear of the seal faces is significantly reduced. It has been shown that circumferentially varying waviness of one of the faces of a mechanical face seal causes such hydrodynamic lubrication.

The objective of this investigation is to examine the performance characteristics of the wavy mechanical face seal by studying the effects of certain design parameters. Seal performance is measured by leakage and wear rate. The …

Investigation Of Evaporation From Grooved Inverted Meniscus Heat Pipe Wicks, Richard Clarke Oliver

Mechanical Engineering ETDs

The heat transfer process for a special class of wick fed grooved heat pipe evaporators was investigated analytically and experimentally. The heat pipes studied had vapor release slots cut through the evaporator wick to enhance removal of the vapor generated in the evaporator. As a result of the slots, the liquid menisci formed between the groove tips and the transport wick rather than at the base of the grooves as normally observed. This type of heat pipe evaporator is referred to as an inverted meniscus design.

A comprehensive survey of the literature was completed to establish the existing state of …

Lower Bounds To Colunm And Plate Buckling Loads, Pen-Yuan Shih

Mechanical Engineering ETDs

The complexity inherent in the theory of elastic stability has resulted in the extensive use of approximate techniques for determining buckling loads. The Rayleigh quotient provides reasonable answers for a surprisingly broad category of problems. However, the quotient is an upper bound to the buckling load and for certain engineering structures, further it is difficult to estimate the error. A rigorous and conservative analysis requires that a lower bound be computed.

There are several techniques for finding lower bounds to eigenvalues but because of various complicating factors none is routinely used for elastic stability analyses. The purpose of this dissertation …

Elastic-Plastic Analysis Of A Flat Ring Subject To Internal Pressure, Wei-Yang Warren Lu

Mechanical Engineering ETDs

An exact elastic-plastic solution for the stresses in a flat ring subject to pressure is obtained on the basis of J₂ deformation theory together with a modified Ramberg-Osgood law. The results are assessed on the basis of Budiansky's criterion for the acceptability of J₂ deformation theory. By using exact elastic-plastic stresses, the radial enlargement and the permanent increase in thickness of the ring at the hole are obtained. Upon release of the pressure, residual stresses around the hole are produced.

Waviness Distortion In Mechanical Face Seals, Joseph J. Roesch

Mechanical Engineering ETDs

In this thesis the phenomenon of waviness distortion in mechanical face seal washers is investigated. Waviness in face seals leads to leakage in some applications. When leakage becomes significant, the seal must be replaced. If the distortion causing mechanism can be described, improvement in seal performance and behavior may be possible.

The components and function of the mechanical face seal are first discussed. It is seen that only one component of the seal unit shows significant deterioration over a period of time. It is also seen that this component, the face washer, wears in a characteristic manner. The characteristics of …

Stresses At The Tips Of Cracks Emanating From The Loaded Fastener Hole, Venkataraman Shivakumar

Mechanical Engineering ETDs

Stress-intensity factors, K, are obtained at the tips of radial cracks emanating from the boundary of an internal circular fastener hole in a plate loaded by a pin or rivet that just fills the hole and is pulled in the negative y-direction, in the plane of the plate. Solutions are obtained in a conformally mapped region in the form of series for different crack lengths and are based on the Muskhelishvili formulation in the two-dimensional theory of elasticity. The method presents a general technique for determining K for k symmetrically located radial cracks of equal length for a wide variety …

A Method Of System Identification With Experimental Investigations Of Real Systems, Paul H. Merritt

Mechanical Engineering ETDs

The following generalized problem was investigated in this study:

"Given a system that can be described by a vector differential equation of the type,

x = f (x, u, a, t) ,

and given both input data, ^u_~ and output data, ^x_~, determine both the general form of the differential equation, ^f_~ (.,.,.,.), and the unknown parameters, ^a_~."

This study describes a method of identifying the parameters, ^a_~, and the form, ^f_~, of the above equation. Initially, the form of the equation must be hypothesized to determine the unknown parameters; …

An Optimal Tracking System For Numerically Controlled Machine Tools, Stephen H. Neff

Mechanical Engineering ETDs

Conventional numerically controlled machine tools use straight line approximations for machining contoured surfaces or outlines. This thesis uses modern control theory to develop an optimal tracking system which will follow any surface defined by a second degree polynomial without resort to straight line approximation. To develop the optimal tracking system, the mathematical expressions required to define the dynamics of a two axis machine tool following a parabolic path are formulated. Next, the third order differential equation representing the slide, driven by a hydraulic motor which is controlled by an electrohydraulic servovalve, is changed into a first order matrix differential equation, …

A Probabilistic Approach To The Design Of Heat Pipes, Charles C. Roberts Jr.

Mechanical Engineering ETDs

The design of heat pipes involves knowledge of phenomena such as surface tension forces, wick permeability, and fluid vaporization and condensation. Considerable variability in these phenomena has been observed in heat pipe experiments. Thus, a probabilistic design model for predicting heat pipe heat transfer rate has been developed taking into consideration uncertainty in the prediction of the above phenomena. The probabilistic model yields a mean, a standard deviation, and the distribution of heat transfer rate based on the means, standard deviations, and distributions of the design parameters. The probabilistic method is compared to experimental data from heat pipes with wire …

Theoretical And Experimental Study Of Explosive Closures Of 6061-0 Aluminum Pipes, Lyle E. Edwards

Mechanical Engineering ETDs

This thesis examines the use of explosives to collapse metal pipes from an applications point-of-view. A particular system is studied, both theoretically and experimentally, in order to facilitate the future design of such closures with the least possible physical testing. The calculations are based on a rigid-perfectly plastic model of the observed deformations of the tubes, and on various assumed am derived properties of the metal and sheet explosives under the dynamic conditions of closure. A computer program has been devised which simulates the actual motion of a pipe during collapse. Experimental work involved actual test firing of aluminum cylinders …

Dynamic And Thermal Studies Of Micron Size Metallic Particles In A Nonequilibrium Low Pressure Argon Plasma Jet, Barry R. Maxwell

Mechanical Engineering ETDs

Dynamic And Thermal Studies Of Micron Size Metallic Particles In A Nonequilibrium Low Pressure Argon Plasma Jet

Strain Measurements At Extremely High Temperatures Using Moiré Fringe Techniques., Joseph W. Neudecker Jr.

Mechanical Engineering ETDs

A new procedure is described for using the moiré-fringe technique to measure strains in structural materials at temperatures exceeding 1300 °C. The principal factor found to be necessary for successful viewing of moiré patterns at extremely high temperatures is the use of reflected laser light for viewing the strained grid on the material. This factor is extensively discussed and experiments are described in which strain measurements were successfully made on graphite specimens at elevated temperatures. It is concluded that the techniques described constitute a more feasible method of measuring strains at higher temperatures than is possible by any other known …

Three Dimensional Elastic Wave Propagation In Bodies Of Revolution, Robert S. Pritchard

Mechanical Engineering ETDs

This dissertation describes solution of a class of problems of three dimensional (non-symmetrical) elastic wave propagation in bodies of revolution. The method of analysis is expansion into circumferential modes followed by solution of an approximate numerical scheme using a digital computer. The material constituting the body has been assumed homogeneous, isotropic, linearly elastic and only one mate­rial may appear in the body. A load may be applied either by a pressure blast or by a target body acting over some portion of the boundary. The loading functions may vary around the circumference. Three dimensional wave motion is analyzed by expanding …

Measurement Of Fluid Velocities In A Simulated Heat Pipe, Lewis Collin Moore

Mechanical Engineering ETDs

Velocity components of numerous geometries may be measured with the laser Doppler technique. Combinations of system parameters were investigated that were useful for constructing a two-dimensional velocimeter for a tube with porous walls. A method was developed which combined a local oscillator with a crossed-incident beam using backscatter at very small angles from the longitudinal axis. Seeding requirements, electronics signal processing, permeability measurements, and measurement point constraints were investigated. Preliminary fluid velocity results were obtained, and recommendations are made for further improvements to overcome the difficulties encountered in the current investigation.

A Numerical Study Of The Coanda Effect., Soloman P. Chavez

Mechanical Engineering ETDs

A numerical solution for the flow in a two-dimensional bistable fluid amplifier is obtained. A minimum Reynolds number is found below which attachment will not occur. The study shows the quality of attachment and attachment point varying with Reynolds number.

Vertical Force Measurement For The Chaparral Rocket Sled, John C. Gustafson

Mechanical Engineering ETDs

A study of the feasibility of instrumenting existing structures with strain sensing elements to measure a specific component of force transmitted by the structure in use has been conducted. A specific structure, the front slipper assembly of the Chaparral rocket sled, was used in this study. The developmental phase of this work was conducted through the use of a model study. The model studies were made to determine appropriate stress raisers and locate strain gages so the desired force component could be measured. The actual structure was modified in accordance with the results of the model tests. Calibration tests and …

Improved Numerical Techniques For Three Dimensional Transient Conduction Coupled With Surface Radiation And Variable Emissivities, Jimmie H. Smith

Mechanical Engineering ETDs

The problem of transient conduction combined with surface radiation and variable emissivities is solved numerically. The existing, but little used, multidimensional Douglas-Peaceman-Rachford alternating-direction-implicit (ADI) technique for finite differencing is chosen as the best available. It is modified and applied to the three-dimensional transient heat equation with source term. Techniques for blocking conduction in excluded directions are demonstrated. Quasi-linearization is used to combine the radiant enclosure calculations with the transient conduction calculations. That is, on an alternating basis, a time step in conduction is followed by a radiant enclosure solution. The radiant enclosure problem is solved in a novel manner, combining …

A Digital Dynamic Data Compensation Technique, George Lee Schulz

Mechanical Engineering ETDs

The output of seismic transducers is proportional to the input only for inputs in specific frequency range. This paper presents a method for extending the usable frequency range of seismic transducers through the use of a digital data processing technique. The method is based on the assumptions that a seismic transducer may be represented by a damped single degree of freedom system and that the output of the transducer is proportional to the relative displacement between the seismic mass and the surface on which the transducer is mounted. The computational technique utilizes a new, efficient, and accurate method of numerical …

A Criterion For Dynamic Low-Cycle Shear Fracture, Teh T. Liu

Mechanical Engineering ETDs

The present investigation establishes a cumulative-damage criterion for specimens subjected to reversed cyclic dynamic shear loads. The empirical equation is found to be:

where

= the change in plastic shear strain at each loading.

= the ultimate shear strain at single loading.

= the empirical exponent to be determined.

Specimens of 6061-T6 aluminum alloy were tested under reversed shear loadings from 1 to 22 applications prior to fracture. The amount of shear deformations was measured at the center part of the critical section. The data was analyzed with the aid of a digital computer. The exponent p in the power …

A Study Of Thermoacoustic Oscillations At Elevated Static Pressures, Michael Einar Berger

Mechanical Engineering ETDs

An experimental investigation was conducted to determine the effect of high static pressure on a closed thermoacoustic sound generator.

The theory for thermoacoustic oscillations is reviewed and analyzed for the case of elevated static pressure. Design equations for high internal pressure oscillators are developed from the principles of dimensional analysis, and a general de­sign equation is proposed.

A closed double-end thermoacoustic oscillator was designed to withstand high temperatures and pressures and was used in the experimental investi9ation. Both air and helium were used as the working gases.

The results of both the theoretical and experimental investigations show that acoustic sound-pressure …

Measurement Of Deformations An A Large Displacement Gradient Field, Lowell P. Martin

Mechanical Engineering ETDs

A summary of the general kinematical theory of finite deformations is presented together with analyses of the specific deformations of sim­ple shear, bending of a block and bending of an initially curved cuboid.

The moiré fringe equations for large homogeneous deformation are developed. The extension to the nonhomogeneous case is presented and specific analyses are given for the deformations noted above. The moiré theory is combined with the results of the large deformation analyses.

Theoretical results are verified by the study of geometrically produced moiré patterns, and by actual experiments conducted on syn­thetic rubber specimens. The experiments included the deformations …

Stress Fluid In The Vicinity Of A Crack, Alfred S. Arcache

Mechanical Engineering ETDs

The purpose of this investigation was to apply the logarithmic hypothesis of the plane elastic dislocation theory to approximate a plane fracture problem. The region of study is essentially elastic except for a very small region in the neighborhood of the crack which is at some undefined plastic state. The model is a large, thin plate, tensile specimen bounded at the interior by a circular hole from which two stable natural cracks are originated. The experimental model was developed by Ju and Shafer, who also obtained the dislocation function along the crack used in the analysis.

The present fracture analysis …

A Three-Component Force Transducer For Monorail Rocket Sleds, Vincent Warren Gorman

Mechanical Engineering ETDs

A three-component force transducer which permits measurement of the vertical force, the cross-track force, and the roll moment about an axis parallel to the track was developed for use on monorail rocket sleds. For this force system it was found that the maximum allowable load for both the vertical and cross-track components was approximately 28,000 pounds, and the maximum allowable roll moment was approximately 45,500 inch-pounds. The transducer, mounted between the slipper and sled, uses strain gages as component sensing elements. The strain gage bridges were statically calibrated for each component of load the transducer was designed to measure. In …

The Dynamic Low Cycle Testing Machine: (Design And Calibration), Michael J. Shannon

Mechanical Engineering ETDs

The design and development of a loading device for subjecting a reversed shear specimen to a pulsed dynamic load is described. The development includes calibration technique to confirm that design criteria had been met. A relationship between plastic deformation and peak tensile load is presented.