Digital Commons Network^™

Simulation And Analysis Of A Drilling Fluid Using A Herschel-Bulkley Model, Daniel Powell

Mechanical Engineering ETDs

In the study, a drilling fluid with known properties is analyzed and simulated in the laminar regime through a pipe with dimensions of 1.5m in length and 0.02m in diameter. The purpose of the conducted analysis is to demonstrate the advantages of the Herschel-Bulkley model currently used in the oil and gas industry for analyzing non-Newtonian drilling fluids.

For comparison, the analysis is also performed using more simple models for non-Newtonian fluids such as the Bingham Plastic model and the Power Law model and for a Newtonian fluid (water). In addition to analytical models, computations are ...

A Visual Velocity Impedance Controller, Victor Nevarez

Mechanical Engineering ETDs

Successful object insertion systems allow the object to translate and rotate to accommodate contact forces. Compliant controllers are used in robotics to provide this accommodation. The impedance compliant controller is one of the more researched and well known compliant controllers used for assembly. The velocity filtered visual impedance controller is introduced as a compliant controller to improve upon the impedance controller. The velocity filtered impedance controller introduces a filter of the velocity impedance and a gain from the stiffness. The velocity impedance controller was found to be more stable over larger ranges of stiffness values than the position based impedance ...

Drag And Shape Analysis Of Fiberglass Particles, Cody Williams

Mechanical Engineering ETDs

Settling tests were performed on particles of NUKON fiberglass to relate the drag coefficient of the particles to the Reynolds number of the particles. A new method was developed to measure fiberglass particles. The projected area, projected perimeter, and average height of the particles are measured using this method. The measurements are used to calculate the measured drag coefficient and measured Reynolds number for the particles. Data collected was compared to previous studies that focused on the settling of sand grains. A predictive correlation that was developed for sand grains was applied towards the particles of fiberglass. Tests were run ...

Mesh Addition Based On The Depth Image (Mabdi), Lucas E. Chavez

Mechanical Engineering ETDs

Many robotic applications utilize a detailed map of the world and the algorithm used to produce such a map must take into consideration real-world constraints such as computational and memory costs. Traditional mesh-based environmental mapping algorithms receive data from the sensor, create a mesh surface from the data, and then append the surface to a growing global mesh. These algorithms do not provide a computationally efficient mechanism for reducing redundancies in the global mesh. MABDI is able to leverage the knowledge contained in the global mesh to find the difference between what we expect our sensor to see and what ...

Non-Destructive Evaluation Of Functional Material Properties Performed On Additively Manufactured Coupons, Devin S. Plagge

Mechanical Engineering ETDs

This thesis presents the development of non-destructive characterization of functional material properties of additively manufactured metals. In particular, this study was focused on the common structural stainless steel alloy, 316L, utilizing a coupon designed specifically for simple modal analysis. Additive manufacturing (AM) has moved to the forefront of the manufacturing world, particularly in aerospace and defense segments because of the potential to produce multi-functional, highly optimized components. The ability to confidently qualify these complex, and thus expensive, components has been lagging behind the advancing technology. The adoption of traditional characterization techniques developed for wrought materials has been most common, and ...

Development And Implementation Of High Fidelity Human Models For The Investigation Of Blast And Non-Penetrating Projectile Impact, Candice F. Cooper

Mechanical Engineering ETDs

Military operations abroad have highlighted the effects of several types of physical traumas including traumatic brain injury and behind armor blunt trauma. While previous approaches toward understanding and mitigating trauma caused by blast or blunt impact relied upon physical testing of animal subjects, post mortem human subjects, or human tissue surrogates, recent advances in computational capability have spurred a growing area of research in computational investigations into wound injury and its mitigation. The development of high-fidelity human torso and head-neck-torso models are presented here. These models are employed in blast and non-penetrating projectile impact simulations in order to demonstrate the ...

Theory, Fabrication, And Experimentation Of Phononic Crystals In Mems At Micro/Nano Scale: Engineering Of Thermal And Rf Phonons To Applications In Thermoelectrics And Microresonators, Seyedhamidreza Alaie

Mechanical Engineering ETDs

Phononic Crystals (PnCs) are novel materials comprised of a periodic structure of inclusions in a matrix. This periodic arrangement creates phononic bandgaps, and modifies phononic bandstructures of a material. Such a property offers promising applications at the micro and nano scales to engineer acoustic filters, high Q-factor resonators, and thermoelectric properties of materials. Studying PnCs at the micro/nano scale requires specific characterization techniques, which rely on Micro Electro Mechanical Structures (MEMS). This work focuses on the study, and characterization of PnCs using MEMS in view of their prospective applications in thermoelectric materials, microresonators and acoustic filters, and also the ...

Gauge Repeatability And Reproducibility Study On A Hemi-Shell With A Brown & Sharpe® Coordinate Measuring Machine (U), Lucas Valdez

Mechanical Engineering Student Publications

In engineering at LANL, everything relies on the quality of a product or process. Today dimensional inspection is a necessity to ensure customer specifications are met to the highest standard. Currently LANL’s main processes for dimensional inspection on hemi-shells are conducted on uniquely designed machines - Sheffield or Shell Measuring Machine (SMM). These specialized rotary contour machines were built to measure only the wall thickness, inner and outer contours of a hemi-shell. These machines are heavily dependent on the inspector and typically have very few personnel trained to use them. With no manufacturer support and age leading to production down ...

Packaging Strategy For High Voltage And High Shock Environments, Kevin Austin

Mechanical Engineering Student Publications

The historical design approach for ensuring survivability in devices that operate at high voltages which would arc in air or that must survive substantial shock loadings employs an encapsulant whose dielectric strength prevents electrical breakdown and whose modulus prevents gross movement of the embedded components. While mostly successful, this approach presents some significant design challenges: (1) the high thermal expansion of the epoxy leads to large stresses during thermal cycles, (2) degassing of the epoxy before cure and careful encapsulation are essential to eliminate voids that could initiate dielectric breakdown, (3) the internal components are embedded deep within an impenetrable ...

Extended Kalman Filter Implementation For The Khepera Ii Mobile Robot, Thomas J. Otahal, Herbert G. Tanner

Mechanical Engineering Faculty Publications

The accurate estimation of robot position and orientation in real-time is one of the fundamental challenges in mobile robotics. The Extended Kalman Filter is a nonlinear real-time recursive time domain filter that combines available sensor data to produce an accurate estimate of state, and has been successfully applied to the localization problem in mobile robotics and aircraft navigation. This report describes an Extended Kalman Filter implementa- tion for the Khepera II mobile robotics platform that seeks to produce accurate localization estimates in real-time using wheel odometry data, IR sensor range data, and compass heading data.

Information Surfing For Model-Driven Radiation Mapping, Andres Cortez, Herbert G. Tanner

Mechanical Engineering Faculty Publications

In this report we develop a control scheme to coordinate a group of mobile sensors for radiation mapping of a given planar polygon region. The control algorithm is based on the concept of information surfing, where navigation is done by means of following information gradients, taking into account sensing performance as well as inter-robot communication range limitations. The control scheme provably steers mobile sensors to locations at which they maximize the information content of their measurement data, and the asymptotic properties of our information metric with respect to time ensures that no local information metric extremum traps the sensors indefinitely ...

Task-Driven Multi-Formation Control For Coordinated Uav/Ugv Isr Missions, Herbert G. Tanner

Mechanical Engineering Faculty Publications

The report describes the development of a theoretical framework for coordination and control of combined teams of UAVs and UGVs for coordinated ISR missions. We consider the mission as a composition of an ordered sequence of subtasks, each to be performed by a different team. We design continuous cooperative controllers that enable each team to perform a given subtask and we develop a discrete strategy for interleaving the action of teams on different subtasks. The overall multi-agent coordination architecture is captured by a hybrid automaton, stability is studied using Lyapunov tools, and performance is evaluated through numerical simulations.

Thermodynamically Consistent Relations Involving Plasticity, Internal Energy And Thermal Effects, Howard Schreyer, Paul Maudlin

Mechanical Engineering Faculty Publications

Experimental data associated with plastic deformations indicate that the temperature is less than that predicted from dissipation based on plastic work. To obtain reasonable correlation between theoretical and experimental results, the plastic work is often multiplied by a constant β. This paper provides an alternative thermodynamic framework in which it is proposed that there is an additional internal energy associated with dislocation pile-up or increase in dislocation density. The form of this internal energy follows from experimental data that relates flow stress to dislocation density and to equivalent plastic strain. The result is that β is not a constant but ...

Increasing The Accuracy Of Cooperative Localization By Controlling The Sensor Graph, Deepti Kumar, Herbert G. Tanner

Mechanical Engineering Faculty Publications

We characterize the accuracy of a cooperative localization algorithm based on Kalman Filtering, as expressed by the trace of the covariance matrix, in terms of the algebraic graph theoretic properties of the sensing graph. In particular, we discover a weighted Laplacian in the expression that yields the constant, steady state value of the covariance matrix. We show how one can reduce the localization uncertainty by manipulating the eigenvalues of the weighted Laplacian. We thus provide insight to recent optimization results which indicate that increased connectivity implies higher accuracy and we offer an analysis method that could lead to more efficient ...

Almost Global Asymptotic Formation Stabilization Using Navigation Functions, Amit Kumar, Herbert G. Tanner

Mechanical Engineering Faculty Publications

We present a navigation function through which a group of mobile agents can be coordinated to achieve a particular formation, both in terms of shape and orientation, while avoiding collisions between themselves and with obstacles in the environment. Convergence is global and complete, subject to the constraints of the navigation function methodology. Algebraic graph theoretic properties associated with the interconnection graph are shown to affect the shape of the navigation function. The approach is centralized but the potential function is constructed in a way that facilitates complete decentralization. The strategy presented will also serve as a point of reference and ...

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 ...

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 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 ...

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 ...

The Development Of A Temperature Probe And Temperature Survey Of The Interaction Of An Oblique Shock Wave And A Turbulant Boundary Layer, Donald M. Yano

Mechanical Engineering ETDs

The purpose of this investigation was to develop a miniature air temperature probe and to measure temperatures in the interaction region of an oblique shock wave and a turbulent boundary layer.

Whole-Field Methods In The Measurement Of Post-Elastic Surface Strains, Siew Poh Chan

Mechanical Engineering ETDs

Several whole-field methods were studied and a new technique was developed for the purpose of measuring post-elastic surface strains in metals. Critical evaluation was given to the following experimental techniques: the moire effect and the birefringent coating.

Transient Response Of Linear Undamped And Lightly Damped Lumped Spring-Mass Systems By Graphica Techniques, Richard O. Brooks

Mechanical Engineering ETDs

Responsive motions of linear undamped and lightly damped lumped spring mass systems subjected to transient inputs can be determined by several methods. All these methods require solving of the differential equation in some manner. Practically all techniques for solving the differential equations involve higher mathematics.

Experimental Investigation Of The Interaction Of An Oblique Shock Wave With A Turbulent Boundary Layer, Amado Arthur Trujillo

Mechanical Engineering ETDs

The purpose of the investigation was to accurately describe the interaction of a shock wave and a turbulent boundary layer based upon the measurement and subsequent analysis of both static and impact pressure throughout the interaction region.

A Study Of Temperature Measurement Precision In Debye-Scherrer Specimens During High Temperature X-Ray Diffraction Measurement Of Thermal Expansion, Roy Glenn Merryman

Mechanical Engineering ETDs

The literature cited covers a comprehensive survey on temperature measurement methods in thermal expansion determination utilizing X-ray diffraction from 1921 through 1961 and a compilation of all published data on the thermal expansion of gold from 1916 through 1960 and magnesium oxide from 1906 through 1961. References for comparison of the MgO results with those of the Bureau of Mines Interlaboratory Program of Thermal Expansion Measurements on MgO are also presented. The literature on temperature measurement was limited to those articles featuring camera design or temperature conditions, since to examine publications on all phases of thermal expansion was found to ...

Determination Of Thermal Stresses At Interior Points, Siegfried Thunborg Jr.

Mechanical Engineering ETDs

Existing theory was used to determine the thermal stresses and strains throughout a long thick walled cylinder under equilibrium thermal conditions when the thermal gra­dient through the wall is dependent on radial position only.

A thick walled cylindrical model, made of a plastic material, was constructed and strain gages were imbedded in and mounted on the cylinder to determine strains at interior and surface locations. The cylinder was subjected to equi­librium and transient thermal conditions and thermal strains were measured. In the equilibrium thermal condition the measured strains were compared with those predicted by theory.

The results show ...

Radial Dislocations In Plane Stress., William J. Sieger

Mechanical Engineering ETDs

The elastic dislocation theory was used to obtain stress potentials for the dual dislocation problem. These solutions give the stress field for an infinite plane region containing a centrally located circular hole with two radial dislocations originating from opposite sides of the hole and extending into the region along a line perpendicular to the axis of applied load. Solutions were obtained for both the case of a linear dislocation relation along the cuts and for a parabolic relation.

Plastic Models For The Study Of Thermal Stresses, Carl W. Theisen

Mechanical Engineering ETDs

The purpose of this thesis was to determine and evaluate an experimental method for accurately measuring thermal stresses in structural shapes subjected to large transient thermal gradients, without introducing the problems of high temperature instrumentation, or expensive and elaborate test facilities. Most experimental methods consist of mounting high temperature strain gages on the prototype or model of the metal structure to be evaluated, thermal shocking the structure and then recording the accompanying strains. This method is used quite extensively in the aircraft field, and in others, where the effects of thermal stresses must be considered. However, problems are encountered when ...

The Development Of A Static Pressure Probe For The Interaction Region Of Shock Waves And Boundary Layers, John Rode

Mechanical Engineering ETDs

The purpose of this investigation was to develop a static pressure probe for measuring static pressures in the region of interaction of a shock wave and a boundary layer. Requirements of such a probe are: small size to permit measurement of pressure variations within the thin boundary layer, pressure coefficient close to unity to permit precise static pressure measurements in regions of unknown and varying velocity and proper response to large pressure gradients.

A Shell-Theory Analysis Of Transient Thermal Stresses In Moderately Thick-Walled Cylinders, Thomas K. Mckinley

Mechanical Engineering ETDs

This paper investigates the validity of extending the concepts of shell theory to transient thermoelastic problems involving moderately thick-walled shells. The region of study is a moderately thick-walled cylinder which is constrained radially at both ends and is exposed to a uniform, time-dependent heating (or cooling) at one end. The cylinder walls are assumed to be adiabatic, and inertia effects are neglected in the development.

It is concluded from the results of this investigation that the extension of shell theory to moderately thick-walled cylindrical regions subjected to axial, time-dependent temperature variations is an analytical method of approach.

Adaptation Of Beggs Deformeter Apparatus To The Solution Of Three-Dimensional Problems, Roland L. Finley

Mechanical Engineering ETDs

In the area of structural analysis and structural design, numerous efforts have been made and more are yet to be made toward solving statically indeterminate problems easily and with a high degree of accuracy. Fortunately, the great majority of such problems can be solved by one or more of the many mathematical methods that are normally used. However, the mathematical solutions become exceedingly difficult if and when it is desired to use irregularly shaped structural members.