Mechanical Engineering Commons^™

Maximum Likelihood Estimation For Distributed Parameter Models Of Large Beam-Like Structures, Ji Yao Shen

Mechanical & Aerospace Engineering Theses & Dissertations

Proposed large space structures have many characteristics that give an advantage to modeling their structural dynamics by a set of partial differential equations (PDE's). By far, the most effort put forth in studying system identification and control to date has been based on finite element models. Despite its acceptability, such lumped parameter models have inevitable deficiencies primarily because of their complexity. Both approaches are complementary and each should be used where it is most effective. But the fact is that the distributed parameter approach has not been developed to the level of maturity as for the lumped parameter approach.

Motivated …

Integrated Control Of Thermally Distorted Large Space Antennas, Robert H. Tolson

Mechanical & Aerospace Engineering Theses & Dissertations

Studies on controlling the thermal distortion of large space antennae have generally investigated a single orbital position and have optimized actuator locations based on minimizing the RMS surface deviation from the original parabolic shape. One study showed the benefits of directly using far zone electric field characteristics as the performance measure; but, this approach resulted in a nonlinear programming problem. The objective of the current study is to develop an approach to designing a control system that (1) recognizes the time dependence of the distortion and (2) controls variables that are directly related to far field performance in a quadratic …

Numerical Investigation Of A Non-Newtonian Material Through A Sudden Pipe Expansion, V. G. Masanja

Tanzania Journal of Engineering and Technology (TJET)

A numerical method for solving two dimensional elliptic boundary-value problems of fourth order is used for finding stationary solutions of the equations of motion for a laminar flow through a sudden pipe expansion of an incompressible non-Newtonian fluid with a constitutive equation of the Reiner-Rivlin (R-R) type. Results for the Newtonian fluid, which is a special case, are in excellent agreement with those by previous investigators and they demonstrate the reliability, superiority and accuracy of the method. Results for the non-Newtonian cases could be of value for fixing ideas about visco-elastic behaviour although the R-R fluid allows only inelasticity: this …

Nonproportionally Loaded Steel Beam-Columns And Flexibly-Connected Nonsway Frames, Siva Prasad Darbhamulla

Civil & Environmental Engineering Theses & Dissertations

A theoretical study of the inelastic stability of nonproportionally loaded steel beam-columns and flexibly-connected frames is conducted. Specifically, solution techniques are formulated to predict the nonlinear behavior of cross sections, spatial beam-columns, and nonsway plane frames under the combined influence of imperfections, flexible connections, and nonproportional loads. A set of new inelastic slope-deflection equations for imperfect members are derived and their use illustrated through in-depth studies of flexibly-connected portal and two-bay two-story frames. These equations are derived from a system of nonlinear ordinary differential equations. The member studies are carried out using a second-order finite-difference solution to a set of …

A Systematic Procedure For The Analysis And Design Of Deployable Space Structures, Praveen Kumar

Mechanical & Aerospace Engineering Theses & Dissertations

An integrated graph theory and a symmetry-based approach have been developed for the type synthesis of deployable truss structures. Using this systematic approach, a bay of a deployable structure may be looked upon as being built around an axis or a plane of symmetry, including anti-symmetry. By providing a fictitious joint along this axis, the problem of structural design and analysis can be reduced to the study of one plane or face of the given structure. Each face is considered to be an assemblage of structural links connected by joints which form a closed kinematic chain. The conventional graph representation …

Application Of Shape Sensitivity Analysis For Computation Of Transient Free-Surface Flows, Frank Nicolas Michel

Mechanical & Aerospace Engineering Theses & Dissertations

Shape sensitivity analysis is introduced into a numerical scheme simulating a transient free-surface flow and applied to the case of a fluid advancing through a bed of cylinders. For this incompressible Newtonian flow, viscous forces are dominant. A penalty function finite element formulation is used to solve the problem. Coordinates of nodes on the moving boundary are chosen as design variables and an analytical formulation of the gradient of the finite element algebraic system, with respect to these variables, is derived.

In a numerical example, the results obtained with and without sensitivity analysis are compared. The efficiency and accuracy of …

A Reiner-Rivlin Fluid Flow Through Entrance Region Of A Circular Pipe, V. G. Masanja

Tanzania Journal of Engineering and Technology (TJET)

The flow of a Reiner-Rivlin fluid with two viscosity coefficients through the entrance region of a circular pipe has been studied numerically. In particular the growth of the entrance length as a function of the Reynolds number and the non-Newtonian parameters has been examined. Where comparison could be made, the results have been compared with existing experimental -and numerical data as well as the limited theoretical work available.

The Development Of An Efficient Lupin Harvesting Front, E D. Blanchard

Journal of the Department of Agriculture, Western Australia, Series 4

Harvest losses represent a significant reduction in lupin production and farm productivity.

Since 1984, the Department's Farm Machinery Research and Liaison Unit at the Dryland Research Institute has studied the lupin harvesting operation to improve its mechanical efficiency. An experimental and a prototype harvesting front were built and tested in the field. Guidlines for efficient lupin harvesting were produced, and commercial modifications developed.

Improved Fertilizing Practices On The Peel-Harvey Catchment, P T. Arkell

Journal of the Department of Agriculture, Western Australia, Series 4

Broad-acre farmers in the Peel-Harvey catchment have met a challange and achieved a great deal since the fertilizer extension programme started in 1983.

The main objective of the extension programme has been to ensure that every year three-quarters of the farmers make economically and technically sound fertilizer decisions, thus causing a minimum amount of phosphorus to enter the waterways of the Peel-Harvey estuarine system.

A Finite Element Formulation For The Large Deflection Random Response Of Thermally Buckled Structures, James Eugene Locke

Mechanical & Aerospace Engineering Theses & Dissertations

The effects of temperature and acoustic loading are included in a theoretical finite element large deflection formulation for thin, isotropic plate and beam type structures. Thermal loads are applied as steady-state temperature distributions, and acoustic loads are taken to be stationary and Gaussian with zero mean and uniform magnitude and phase over the surface of the structure. Material properties are considered to be independent of temperature. Also, inplane and rotary inertia terms are assumed to be neglegible, and all inplane edge conditions are taken to be immovable. For the random vibration analysis, cross correlation terms are included.

The nature of …

Lb 838 Machinery And Equipment Museum, Tractor Museum

Lester F. Larsen Tractor Museum: Planning and Development Documents

Established the Antique Farm and Equipment Committee. To provide for the creation of a museum.

Coupled Bending-Torsion Steady-State Response Of Pretwisted, Nonuniform Rotating Beams Using A Transfer-Matrix Method, Carl E. Gray Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

Using the Newtonian method, the equations of motion are developed for the coupled bending-torsion steady-state response of beams rotating at constant angular velocity in a fixed plane. The resulting equations are valid to first order strain-displacement relationships for a long beam with all other nonlinear terms retained. In addition, the equations are valid for beams with the mass centroidal axis offset (eccentric) from the elastic axis, nonuniform mass and section properties, and variable twist. The solution of these coupled, nonlinear, nonhomogeneous, differential equations is obtained by modifying a Hunter linear second-order transfer-matrix solution procedure to solve the nonlinear differential equations …

Analyses Of Quasi-Isotropic Composite Plates Under Quasi-Static Point Loads Simulating Low-Velocity Impact Phenomena, Ajit Dhundiraj Kelkar

Mechanical & Aerospace Engineering Theses & Dissertations

Composite laminates have high strength to density ratios that make them attractive for use in aircraft structures. However, the damage tolerance of these materials is limited because they have very low ultimate strains, no plastic deformation range, and no usable strength in the thickness direction. These limitations are very obvious when laminates are subjected to impact loads. Due to these impact loads, laminates suffer visible and invisible damage. To improve the material performance in impact requires a better understanding of the deformation and damage mechanics under impact type loads.

In thin composite laminates, the first level of visible damage occurs …

Identification Of Technical Skills Required Of Industrial Robot Maintenance Technicians In Manufacturing, David James Goetz

Graduate Research Papers

The primary purpose of this study was to identify those technical skills required of industrial robot maintenance technicians in manufacturing.

Specifically, the study:

1) obtained the work/training background of industrial robot maintenance technicians active in the field,

2) identified the technical skills required of industrial robot maintenance technicians, and

3) identified the desired technical skills of industrial robot maintenance technicians.

A secondary purpose of the study was to provide manufacturing engineers/supervisors with a baseline for detailing a training program for robot maintenance personnel.

Liquid Transmission Line Pulser Circuit For Laser Excitation, Carl Stultz

Dissertations and Theses

The subject of this thesis is the study of liquid dielectric transmission lines and their potential application as an excitation source in high speed, high-repetition rate laser designs. The design problems associated with the construction of high repetition rate (khz), short wavelength lasers have been reviewed and the major shortcomings of conventional electrical driving circuits identified. The identification of these shortcomings and a review of the available literature on electrical circuits for various types of lasers suggested that liquid dielectrics and transmission lines could potentially have significant advantages over more conventional circuitry used in high repetition rate, short wavelength lasers. …

On The Space Shuttle Wing Thermal-Structural Analysis, Kumar Krishna Tamma

Mechanical & Aerospace Engineering Theses & Dissertations

A finite element approach for efficient thermal-structural analysis of structures with thermal protection systems (TPS) is described. The approach is applied to Space Shuttle wing structure configurations subjected to reentry heating. New two and three-dimensional finite elements are developed to model heat transfer in the TPS and supporting structure. A typical TPS/Structural element predicts transient nonlinear temperature variations through the TPS thickness and detailed structural temperatures at the TPS/Structure interface. The accuracy of the TPS/Structure approach in two and three-dimensions is evaluated by comparisons with the conventional approach for various configurations of the wing structure. The results indicate that the …

An Apparatus For Measuring The Thermal Conductivity Of Cast Insulation Materials, Christine A. Wilkins, Robert L. Ash

Mechanical & Aerospace Engineering Faculty Publications

A steady-state apparatus has been developed for measuring the thermal conductivity of cast materials. The design has employed a novel thermal symmetry arrangement which can permit total electrical isolation of the test material from its surroundings. © 1980 American Institute of Physics

Reduction Of Capacitor Switching Transients By Controlled Closing, John Herman Brunke

Dissertations and Theses

This thesis presents the theory, analysis, testing and implementation of a scheme to reduce shunt compensation capacitor switching transients. The described method is switch the capacitors very near the instant when the bus voltage is at a power frequency zero. This was accomplished with a vacuum breaker on a 230 kV shunt capacitor bank.

Finite Element Model Of A Timoshenko Beam With Structural Damping, Louis Ablen Roussos

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical integration technique, a modified version of the Newmark method, is applied to transient motion problems of systems with mass, stiffness, and small nonlinear damping. The nonlinearity is cast as a pseudo-force to avoid repeated recalculation and decomposition of the effective stiffness matrix; thus, the solution technique is dubbed the "pseudo-force Newmark method." Comparisons with exact and perturbation solutions in single-degree-of-freedom problems and with a Gear-method numerical solution in a cantilevered Timoshenko beam finite element problem show the solution technique to be efficient, accurate, and, thus, feasible provided the nonlinear damping is small. As a preliminary step into the …

The Design And Construction Of A Flashlamp-Pumped Frequency-Doubled Dye Laser Applicable To Long Path Monitoring Of Air Pollutants, Joel Craig Johnson

Dissertations and Theses

The subject of this thesis is the development of a laser light source which could be used in an air pollution monitor to measure the average concentration of sulfur dioxide gas over long paths (>1 km). Many of the problems encountered in designing a long-path pollutant monitor such as instrument cost and reliability, the selection of an optimum spectral region for making the measurement, and light losses due to scattering and turbulence, are considered. The result of these considerations together with a survey of available laser light sources suggested that a frequency-doubled dye laser possessed several advantages over other …

Service And Spare Parts, D Hosken

Journal of the Department of Agriculture, Western Australia, Series 4

Service is the preparation, delivery and after-sales maintenance of machinery. It involves responsibilities for both the dealer and the purchaser.

There's Little To Choose Between Scarifier Points, C R. Lester

Journal of the Department of Agriculture, Western Australia, Series 4

Tests on scarifier points showed that methods of treating them to prolong their life had little effect.

Getting The Best From Tractor Tyres, J Quealy

Journal of the Department of Agriculture, Western Australia, Series 4

The amount of pull a tractor develops depends largely on tyre efficiency and so with so many tyre size options for the one tractor model it is very easy to make the wrong decision on tyre fitment.

Tyre efficiency varies with tractor weight, soil conditions, inflation pressure and tyre size.

Hers we look at some of these factors and how changing them may affect efficiency.

Calibration Of Boom Sprays, J R. Peirce

Journal of the Department of Agriculture, Western Australia, Series 4

Boom sprays have become increasingly common on Western Australian farms, allowing farmers to take advantage of modern herbicided.

Most boom sprays used on farms have 50 cm nozzle spacings and require calibrating regularily to ensure accurate herbicide application.

By following these steps, the boom will deliver accurate amounts of herbicide.

How To Select A Tractor, W T. Brown

Journal of the Department of Agriculture, Western Australia, Series 4

A look at some of the factors to be considered when choosing a tractor for your farm. There is no one answer

Replacing Farm Machinery, R Crossman

Journal of the Department of Agriculture, Western Australia, Series 4

In talking of machinery replacement it seems implied that the replacement items of plant are bigger and therefore better than their predecessers. It is also implied that plant replacement is becoming more costly.

Before any decision to replace machinery, the reason for replacement should be carefully considered.

There may be alternatives to the bigger and better solution.

Options For Machinery And Labour, A F. Herbert

Journal of the Department of Agriculture, Western Australia, Series 4

Machinery is one of the highest costs in farming today. It is not unusual for capital investment in machinery to be 20 to 30 percent of the total investment in the farm.

On an annual basis, expenditure directly attributable to machinery can be 40 per cent or more.

This article cannon be a panacea for everyone to reduce machinery costs - each farm is different. But some of the issues might be of help.

Simplifying Lubricants For Farm Machinery, R A. Platt

Journal of the Department of Agriculture, Western Australia, Series 4

All moving parts on machinery needs lubrication. With the rapid development in farm machinery and its attendant sophistifications, the stresses imposed on the lubricants have also increased.

This article looks at some of the changes in requirements and developments in lubricants available.

Matching Tractors And Implements, I W. Grevis-James

Journal of the Department of Agriculture, Western Australia, Series 4

Tractor and implement matching involves balancing implement load characteristics with tractor output characteristics to obtain the best output from the combination. Too much or too little can be costly.

Crutching Cradles Can Work Well, N M. Marney, R. A. Mills

Journal of the Department of Agriculture, Western Australia, Series 4

Crutching cradles allow successful do-it-yourself crutching if a continuous flow of sheep can be maintained. This article describes some units available and discusses costs.