Mechanical Engineering Commons^™

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 …

Heat Transfer In Beaded Thermocouples Mounted On Solid Substrates-- Application To Transient Measurement Errors, Karl Wally

Mechanical Engineering ETDs

Beaded thermocouples mounted on the surface of a solid for the purpose of measuring surface temperature are liable to introduce measurement errors as a result of heat transfer between the surface and the bead, and also because of the thermal inertia of the bead. For the prediction or correction of such errors, an accurate model of the thermocouple response is required. This paper uses a solution technique known as Quasi-Coupling to solve for the heat transfer in idealized beaded thermocouples mounted on idealized solids. The parameters controlling the thermocouple response are identified and the sensitivity of the response to these …

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.

Analysis Of A Heat Pipe Heat Exchanger, Joseph Olorunfemi Amode

Mechanical Engineering ETDs

One of the more promising applications of the heat pipe is in heat exchangers. Heat pipe heat exchangers may be used as recuperators in heating and ventilating systems, in gas turbines, in steam power plants, and in various process industry applications.

An analysis of the heat pipe heat exchanger was conducted in order to help optimize its performance. A computer program was developed to predict heat pipe performance, finned-tube heat exchanger performance, and the overall per­formance of a finned-tube heat pipe heat exchanger. The computer analysis uses conventional heat exchanger design techniques and a new heat pipe design technique which …

Numerical Investigation Of The Flow Of A Stratified Fluid Past A Flat Plate, David L. Eddingfield

Mechanical Engineering ETDs

The two dimensional stratified flow past a flat plate is investigated numerically. The coordinates are stretched with a hyperbolic tangent mapping in order to place the computational boundaries at a sufficiently large distance from the plate. The growth of a boundary layer from the back of the plate as reported by R. R. Long was confirmed numerically. The boundary layer is found to increase in thickness from the back of the plate for values of the ratio of the Reynolds number to the Richardson number up to at least 20. In addition, the upstream influence of the plate is found …

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 …

Plastic Relaxation Around Crack Tip In Composite Materials, Chung-Yen Huang

Mechanical Engineering ETDs

The concept of continuously distributed dislocations is used to investigate the mechanical behavior of fractured composite materials,

As a first approximation to the complicated physical configuration of a composite material, the current investigation concerns a simp1ified physical model by considering an elastic circular cylindrical inclusion imbedded and located in an infinite elastic medium such that an internal line crack starts from the interface and extends in the radial direction of the inclusion. The plastic zone spreads and extends from the crack tip when the entire system is subjected to a uniformly distributed shear load at infinity. This constitutes an anti-pane …

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, …

Analysis Of A High-Heat-Flux Water Heat Pipe Evaporator, Michael Einar Berger

Mechanical Engineering ETDs

An analysis was made to determine a surface which has potential use in a high-heat-flux, low-temperature-drop water heat pipe evaporator. A comprehensive survey of the literature was made to determine those surfaces which had high-heat-flux potential under evaporation. A circumferentially grooved surface was selected as the surface to be analyzed. Two groove geometries were selected for analysis, rectangular and triangular. A mathematical model of the grooves was constructed in order to predict the maximum surface heat flux capability. In addition, a model of the heat transfer within the fluted surface was proposed which postulated that conduction through the wall and …

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 …

A Generalized Elastic Theory Of Fracture, Richard V. Browning

Mechanical Engineering ETDs

A theory of fracture is proposed for brittle and near brittle fracture. The theory includes the Griffith-Irwin theory as a special case. Developed for opening mode loading in plane geometry, the theory is based on a solution for a slit in an infinite elastic plate with an arbitrary relative displacement along the slit. Particular relative displacement functions are chosen and studied in detail by calculating the mean stress, maximum shear stress, maximum tensile stress, and energy density fields as well as the tractions applied on the slit. The particular solutions chosen for examination all exhibit singularities in the stress fields …

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 …

A Time Domain Deconvulution Technique For The Correction Of Transient Measurements., Larry Wayne Bickle

Mechanical Engineering ETDs

Techniques for correcting transient measurements can be considered as "deconvolving" or solving the convolution integral equation

R(t)=F(0) * C(t) + ∫t_0 C(t- Τ) [dF(T)/dT] dT

for the input, F(t), given the response, R(t), and response of the measurement system to a step input of unit magnitude, C(t). Because the deconvolution process is mathematically ill conditioned, it is usually necessary to place additional constraints on the functions F(t), C(t) and/or R(t).

In this paper, a numerical time domain deconvolution

(TDD) technique that provides physical insight into the problems of correcting transient measurements is presented and compared to techniques that have previously …

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.

Improved Numerical Techniques And Solution Of A Separated Interaction Of An Oblique Shock Wave And A Laminar Boundary Layer., Ben Douglas Gay

Mechanical Engineering ETDs

Initial, boundary and differencing techniques of numerical gas dynamics were improved, and a separated interaction of an oblique shock wave and a laminar boundary layer was solved numerically.

The computing time of a Lax-Wendroff differencing technique was reduced 60 percent by making algebraic changes. Inflow and wall boundary techniques were improved, and the new techniques were verified by satisfactory solutions of plain laminar boundary layers and unseparated interactions of oblique shock waves and laminar boundary layers. The differencing technique was numerically unstable for separated interactions.

Results of a sample all-centered differencing technique agreed with those of a Lax-Wendroff technique for …

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 …

Response Of A Nonlinear System To Random Vibration, James Darrell Gibson

Mechanical Engineering ETDs

Response statistics are obtained for a nonlinear, single-degree-of-freedom system subjected to a Gaussian, white noise random excitation. The system has nonlinear damping as well as nonlinear stiffness. The stationary joint probability density function is obtained as the numerical solution to the appropriate Fokker-Planck equation for the nonlinear system being considered. The first order probability density function, the mean square displacement, the average frequency of the response, and the average number of crossings of an arbitrary displacement level are subsequently obtained. These response statistics are compared with those obtained experimentally by simulating the nonlinear system under investigation on a solid state …

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 …