Engineering Commons^™

Additive Manufacturing Powder Removal, Madison A. Lignell, Tyler W. Laird, Kurt K. Reed

Mechanical Engineering

Metal powder-bed fusion is an additive manufacturing process which enables the creation of unique shapes in metal parts that would otherwise be difficult, expensive, or impossible to machine. Metallic powder is melted and fused together by either a laser or electron beam to produce parts quickly. The excess powder covers newly printed parts and can be difficult to remove from small internal features. The scope of this project is to design a device that effectively removes the powder from newly printed parts safely, while reclaiming as much powder as possible for reuse. The solution for this project must be able …

Treadmill User Centering, Cecilia Hill Yan Yuen, Donavan Chandler Feliz, Ariel Mae Arce Crisostomo, Adam Charles Patrella

Mechanical Engineering

The goal of team CENTREAD was to design a device to allow a person with a visual disability to run efficiently and effectively on a treadmill without fear of falling off or injuring themselves. The customer wished for the device to be small, lightweight, and have an easy, autonomous setup, while providing feedback to the user wirelessly for them to correct their own movement. The ultimate goal of the device is to allow the user to be comfortable, safe, and free while using it in order to ensure they have the best running experience. The device utilizes ultrasonic sensors in …

Rotordynamic Analysis Of Theoretical Models And Experimental Systems, Cameron R. Naugle

Master's Theses

This thesis is intended to provide fundamental information for the construction and

analysis of rotordynamic theoretical models, and their comparison the experimental

systems. Finite Element Method (FEM) is used to construct models using Timoshenko

beam elements with viscous and hysteretic internal damping. Eigenvalues

and eigenvectors of state space equations are used to perform stability analysis, produce

critical speed maps, and visualize mode shapes. Frequency domain analysis

of theoretical models is used to provide Bode diagrams and in experimental data

full spectrum cascade plots. Experimental and theoretical model analyses are used

to optimize the control algorithm for an Active Magnetic Bearing …

Distributed Sensing And System Identification Of Cantilever Beams And Plates In The Presence Of Weak Nonlinearities, Patrick Sean Heaney

Mechanical & Aerospace Engineering Theses & Dissertations

While the mathematical foundation for modal analysis of continuous systems has long been established, flexible structures have become increasingly widespread and developing tools for understanding their mechanics has become increasingly important. Cantilever beams and plates, in particular, have been extensively studied due to their practical importance as approximations of more complex structures. The focus of this thesis is on understanding the dynamics of vibrating cantilever beams and plates through analytical and experimental investigation. Various models for the mechanics of these structures, of varying physical fidelity, are described and compared. A fiber optic sensing system is utilized to experimentally acquire distributed …

Dynamics Of A Circular Cylinder In Close Proximity To A Wall, Yargo Teixeira Gomes De Melo

Master’s Theses

The effect of wall proximity on the mechanism of flow-induced vibration of a circular cylinder mounted in a wind tunnel and free to vibrate with two degrees-of-freedom near a rigid plane boundary were examined at a Reynolds number of 1.86 x 10⁵. Hot-wire anemometry and cylinder-mounted accelerometers were used to characterize the flow-induced vibration of the cylinder. In the near wall region (gap ratios, G/D< 0.4) the system was found to exhibit symptoms of movement-induced vibration resulting from the push-and-draw effect of the cylinder pushing into and out of the fluid immediately upstream and downstream of the cylinder. The variation of the width of the separated wake region with the cylinder motion produces a force in phase with the cylinder velocity, resulting in excitation of the cylinder motion. For G/D > 1.0, the alternate shedding of vortices (the Kármán vortex street) produces a fluctuating lift on the body. The lift force also has an associated drag fluctuation at twice the vortex shedding frequency For …

Hydrophobicity Of Low Temperature Vibrating Surfaces, Christian Fergusson

Theses and Dissertations

This study proposes a method to enhance the anti-icing capabilities of superhydrophobic surfaces by utilizing vibration to further reduce contact time of an impacting droplet in addition to keeping the droplet in the Cassie-Baxter regime, where surface adhesion is lower than the opposing Wenzel regime. We tested this with two methods: by investigating the effects of vibration normal to the plane of a superhydrophobic surface being impacted by water droplets in a room temperature environment, with the surface horizontal in a room temperature environment and tiled in a subzero degree environment. The amplitude and frequency of the vibration were varied …

Rotordynamic Enhancement By Utilizing The Controlled Hydrostatic Injection Of Hybrid Air Foil Bearing, Behzad Zamanian Yazdi

Mechanical and Aerospace Engineering Dissertations

Air foil bearings (AFBs) are introduced as promising bearings for oil-free turbomachinery applications. Air foil bearing (AFB) technology has made substantial advancement during the past decades and found its applications in various small turbomachinery. AFBs provide reliable operation at high speed and high temperature with negligible power loss. However, rotordynamic instability, friction and drag during the start/stop, and thermal management are still challenges for further application of the technology. Hybrid Air Foil Bearing (HAFB) technology utilizes the radial injection of externally pressurized air into the traditional hydrodynamic AFB’s film thickness through orifices attached to the top foil. HAFB is one …

The Influence Of Macroscale Stress Concentrations On The Near-Resonant Thermomechanics Of Mock Energetic Materials, Lauren A. Cooper, Allison R. Range, Jeffrey F. Rhoads

The Summer Undergraduate Research Fellowship (SURF) Symposium

The characterization of particulate composite energetic materials, both with and without stress concentration, is currently of great interest to the defense community. This work seeks to further characterize the self-heating effect of composite energetic plates, particularly around regions of high stress, when subjected to harmonic excitation near resonance. Mock energetic plates with macroscale stress concentrations are prepared in various compositions based on the PBXN-109 formulation, and are tested near the first resonant frequency using an electrodynamic shaker. The resulting mechanical and thermal responses are recorded using a laser Doppler vibrometer and an infrared camera, respectively. Upon comparison between the regions …

Measurement And Analysis Of The Physical And Climatic Distribution Environment For Air Package Shipment, David Guadagnini

Master's Theses

The modern air parcel distribution industry has significantly grown to become one of the most commonly employed methods to quickly transport goods throughout the world. Although it comes with many benefits, including higher speed, greater reliability, and tighter security, the multimodal transport system within it can expose packages to a wide variety of climatic and physical distribution hazards. In a single route of transportation, packages could be included in different types of small delivery vans, large commercial semi trucks, cargo dollies, feeder aircraft, and high altitude commercial jetliners. The varying hazard level presented during distribution could directly weaken the packaging …

Frequency Tuning Of Vibration Absorber Using Topology Optimization, Swapnil Subhash Harel

Mechanical and Aerospace Engineering Theses

A tuned mass absorber is a system for reducing the amplitude in one oscillator by coupling it to a second oscillator. If tuned correctly, the maximum amplitude of the first oscillator in response to a periodic driver will be lowered, and much of the vibration will be ’transferred’ to the second oscillator. The tuned vibration absorber (TVA) has been utilized for vibration control purposes in many sectors of Civil/Automotive/Aerospace Engineering for many decades since its inception. Time and again we come across a situation in which a vibratory system is required to run near resonance. In the past, approaches have …

Energy Localization And Heat Generation In Composite Energetic Systems Under High-Frequency Mechanical Excitation, Jesus O. Mares

Open Access Dissertations

In this work, the ability to use high frequency mechanical excitation to generate significant heating within plastic bonded explosives, as well as single energetic particles embedded within a viscoelastic binder, is studied. In this work, the fundamental mechanisms associated with the conversion of high-frequency mechanical excitation to heat as applied to these composite energetic systems are thoroughly investigated.

High-frequency contact excitation has been used to generate a significant amount of heat within samples of PBX 9501 and representative inert mock materials. Surface temperature rises on the order of 10 °C were observed at certain frequencies over a range from 50 …

Development Of An Analytical Model For Beams With Two Dimples In Opposing Directions, Mofareh H. Ghazwani

Masters Theses

Structures such as beams and steel plates can produce potentially high levels of unwanted vibrations and noises in the environment. A method of improving the vibration and acoustic characteristics of beams based on introducing dimples on its surfaces will be presented in this study. This method focuses on creating two dimples in the same and opposite direction on beam’s surface where the effect of dimples on the change in beam’s natural frequencies is the problems of interest.

A boundary value model (BVM) is developed for a beam with two dimples and subjected to various boundary conditions using Hamilton’s Variational Principle. …

Vibration Monitoring Via Nano-Composite Piezoelectric Foam Bushings, David T. Fullwood, Evan T. Bird, A Jake Merrell, Brady K. Anderson, Cory N. Newton, Parker G. Rosquist, Anton E. Bowden, Matthew K. Seeley

Faculty Publications

Most mechanical systems produce vibrations as an inherent side effect of operation. Though some vibrations are acceptable in operation, others can cause damage or signal a machine’s imminent failure. These vibrations would optimally be monitored in real-time, without human supervision to prevent failure and excessive wear in machinery. This paper explores a new alternative to currently-used machine-monitoring equipment, namely a piezoelectric foam sensor system. These sensors are made of a silicone-based foam embedded with nano- and micro-scale conductive particles. Upon impact, they emit an electric response that is directly correlated with impact energy, with no electrical power input. In the …

Nonlinear Vibration Energy Harvesting Based On Variable Double Well Potential Function, Wei Yang, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

Converting ambient mechanical energy to electricity, vibration energy harvesting, enables powering of the low-power remote sensors. Nonlinear energy harvesters have the advantage of a wider frequency spectrum compared to linear resonators making them more efficient in scavenging the broadband frequency of ambient vibrations. To increase the output power of the nonlinear resonators, we propose an energy harvester composed of a cantilever piezoelectric beam carrying a movable magnet facing a fixed magnet at a distance. The movable magnet on the beam is attached to a spring at the base of the beam. The spring-magnet system on the cantilever beam creates the …

Electromechanical Modeling Of A Honeycomb Core Integrated Vibration Energy Converter With Increased Specific Power For Energy Harvesting Applications, Nataraj Chandrasekharan

All Dissertations

Innovation in integrated circuit technology along with improved manufacturing processes has resulted in considerable reduction in power consumption of electromechanical devices. Majority of these devices are currently powered by batteries. However, the issues posed by batteries, including the need for frequent battery recharge/replacement has resulted in a compelling need for alternate energy to achieve self-sufficient device operation or to supplement battery power. Vibration based energy harvesting methods through piezoelectric transduction provides with a promising potential towards replacing or supplementing battery power source. However, current piezoelectric energy harvesters generate low specific power (power-to-weight ratio) when compared to batteries that the harvesters …

Development, Optimization, And Implementation Of A Vibration Based Defect Detection Algorithm For Railroad Bearings, Amy Gonzalez

Theses and Dissertations - UTB/UTPA

Of the three main rail accident types in the United States, derailments are the most common. Studies have shown that derailments occurring above 25 mph are caused by equipment failures such as bearing failures. As a preventative measure, condition-monitoring systems are required to detect defective bearings in the field. Based on data compiled from multiple experiments of healthy and defective bearings at UTPA, an algorithm has been devised to identify bearing abnormalities. Vibration analysis techniques are utilized to potentially determine whether a bearing is defective and the defect type and size using the acquired vibration signatures. Implementation of a defect …

Vibration Table For Environmental Chamber, Michael Czabaranek, Dylan De Caussin

Mechanical Engineering

No abstract provided.

Analysis Of Vibroacoustic Properties Of Dimpled Beams Using A Boundary Value Model, Kyle R. Myers

Dissertations

Attention has been given recently to the use of dimples as a means of passively altering the vibroacoustic properties of structures. Because of their geometric complexity, previous studies have modeled dimpled structures using the finite element method. However, the dynamics of dimpled structures are not completely understood. The goal of this study is to provide a better understanding of these structures through the development of a boundary value model (BVM) using Hamilton's Variational Principle. The focus of this study is on dimpled beams, which represent the simplest form of a dimpled structure.

A general model of a beam with N …

Vibration Based Planetary Gear Analysis And Damage Detection, Rene Sawatzky

Master's Theses

With this thesis the research at the engineering department is continued, based on previous thesis projects. These projects were considering the possibility of simulation gears with rigid bodies. After researches with different emphasizes on the rigid body simulation, the gained knowledge showed limitations of the rigid body model. Gear failures are very diverse and the actual simulation technique could not represent all necessary failure modes that can occur. That led to this thesis as a research project to find a way to detect and analyze the failure modes that cannot be considered with the current rigid body approach. With the …

The Influence Of Gaps On The Frequency Response Of A Beamspring Contact System, Wenbin Zhang

Open Access Theses

Some mechanical systems with gaps such as in disc brakes and Cardan joints exhibit nonlinearity under certain load conditions, which is unpredictable and highly sensitive to initial conditions. Previous studies were mainly focused on either a single-degree-of-freedom (DOF) system or a flexible beam with uniform elastic foundation. The analysis of this thesis is a combination of these two where gaps are first introduced to a flexible beam model. A model of a beam resting on compliant foundation with gaps has been developed and analyzed. The assumed modes method is used to derive the equations of motion (EOM's) for the system. …

Understanding Chassis Inputs From The Rear Suspension Of A Snowmobile, Jamie L. Kleinendorst

Dissertations, Master's Theses and Master's Reports - Open

Today’s snowmobile industry faces great challenges in the field of noise & vibration. The area of main concern is the pass-by noise restriction defined by the Society of Automotive Engineers (SAE) test standard J192, with a maximum sound pressure level of 78 dB(A) being required by many states and national parks. To continue meet or beat this requirement without effecting machine performance, a deeper understanding of the sound transfer paths is required. This thesis examines the transfer paths created by the tunnel, rear suspension, drive shaft, and rubber composite track, with the primary source being suspension input through the ground. …

Crane Shaking Platform Design, Bixing Yan, Andrea Vacca

The Summer Undergraduate Research Fellowship (SURF) Symposium

Most of the control methodology of Mobile hydraulic crane is not as energy efficient as people think or want, and the desire to innovate novel, energy-efficient control strategy is the target of most hydraulic experts. To develop or test the control method under real road and off-road conditions, a platform that could simulate the movement and vibration of the crane truck is desired. To design and build the multi-operation platform, a design process includes brain storming, design selection, FEA (Fundamental Element Analysis), mechanical sizing, hydraulic sizing and Bill of Material is required and preferred. After going through all the steps …

Near-Field Pressure Distributions To Enhance Sound Transmission Into Multi-Layer Materials, Andrew Martin Jessop

Open Access Dissertations

The large impedance difference between air and most solids prevents significant energy transfer from incident acoustic waves across the air-material interface. Refraction also plays a role in preventing acoustic transmission, as the wave speed difference between air and solid materials results in an increase of the resulting propagation angles, creating near-field pressure distributions in the solid material. By utilizing evanescent pressure distributions, which decay normal to the usual direction of propagation and are represented as plane waves propagating with complex angles, energy propagation through the interface can be increased in the subsonic region of wave propagation: i.e., where waves typically …

Acoustic And Dynamic Characteristics Of A Complex Urban Turnout Using Fibre-Reinforced Foamed Urethane (Ffu) Bearers, Sakdirat Kaewunruen

Sakdirat Kaewunruen

A special track system used to divert a train to other directions or other tracks is generally called ‘railway turnout’. A traditional turnout system includes rails, switches, crossings (special track components), steel plates, fasteners, screw spikes, timber bearers, ballast and formation. The wheel rail contact over the crossing transfer zone has a dip-like shape and can often cause detrimental impact loads on the railway track and its components. The large impact also emits disturbing noises (either impact or ground-borne noise) to railway neighbors. In a brown-field railway track where an existing aged infrastructure requires renewal or maintenance, some physical constraints …

Transient Small Wind Turbine Tower Structural Analysis With Coupled Rotor Dynamic Interaction, George R. Katsanis

Master's Theses

Structural dynamics is at the center of wind turbine tower design - excessive vibrations can be caused by a wide range of environmental and mechanical sources and can lead to reduced component life due to fatigue, noise, and impaired public perception of system integrity. Furthermore, periodic turbulent wind conditions can cause system resonance resulting in significantly increased structural loads. Structural vibration issues may become exacerbated in small wind applications where the analytical and experimental resources for system verification and optimization are scarce. This study combines several structural analysis techniques and packages them into a novel and integrated form that can …

Vibration And Acoustic Properties Of Honeycomb Sandwich Structures Subject To Variable Incident Plane-Wave Angle Pressure Loads, Jiaxue Yan

All Theses

Honeycomb structures are widely used in many areas for their material characteristics such as high strength-to-weight ratio, stiffness-to-weight, sound transmission, and other properties. Honeycomb structures are generally constructed from periodically spaced tessellations of unit cells. It can be shown that the effective stiffness and mass properties of honeycomb are controlled by the local geometry and wall thickness of the particular unit cells used. Of particular interest are regular hexagonal (6-sided) honeycomb unit cell geometries which exhibit positive effective Poisson's ratio, and modified 6-sided auxetic honeycomb unit cells with Poisson's ratio which is effectively negative; a property not found in natural …

Vibration And Buckling Of Carbon Nanotube, Graphene, And Nanowire, Mohammad Hadi Mahdavi

Electronic Thesis and Dissertation Repository

Nanostructured materials with superior physical properties hold promise for the development of novel nanodevices. Full potential applications of such advanced materials require accurate characterization of their physical properties, which in turn necessitates the development of computer-based simulations along with novel experimental techniques. Since controlled experiments are difficult for nanoscale materials and atomic studies are computationally expensive, continuum mechanics-based simulations of nanomaterials and nanostructures have become the focal points of computational nano-science and materials modelling.

In this study, emphasis is given to predicting the mechanical behaviour of carbon nanotube (CNT), graphene, nanowire (NW), and nanowire encapsulated in carbon nanotube (NW@CNT), which …

Health Diagnosis Of Lithium-Ion Battery Cell Using Vibration-Based Test And Analysis, Huan Le Pham

Open Access Theses

With their superior advantages of high capacity and low percentage of self-discharge, lithium-ion batteries, which are most commonly used as power sources for hand-held electronic devices, have become the most popular choice for power storage in electric vehicles. Due to the increased potential for long life of lithium-ion batteries in vehicle applications, manufacturers are pursuing methodologies to increase the reliability of their batteries. Methods are now being developed to monitor the health of lithium-ion batteries throughout their life cycle. The work in this thesis is focused on utilizing non-destructive vibration diagnostic testing methods to monitor changes in the physical properties …

Defect Detection In Railroad Tapered-Roller Bearings Using Vibration Analysis Techniques, Iris L. Alvarado

Theses and Dissertations - UTB/UTPA

Derailments can often lead to great damage, loss of lives, and massive costs associated with the railroad infrastructure. A significant cause of derailments is premature bearing failure, and therefore bearing condition-monitoring systems that can detect developing defects are of great importance. Based on an investigation conducted at the University of Texas-Pan American on the development of a vibration and temperature monitoring system, an algorithm is devised utilizing various vibration analysis techniques. The proposed algorithm determines whether a bearing is defective, the type of defect present, the defective component (i.e. cup, cone, or roller), and the size of the defect. Speed-dependent …

The Dynamics Of Rotor With Rubbing, Jerzy Sawicki, Joe Padovan, Rabih Al-Khatib

Jerzy T. Sawicki

This paper presents the description of some phenomena associated with dynamic behavior of rotors interacting with stationary components. Numerical simulations show rotor vibration spectrum rich in subharmonic, quasi-periodic, and chaotic vibrations. The nonlinear calculation techniques are applied to demonstrate the changes of the vibration patterns for different operating conditions. Some conclusions are discussed with regard to unique characteristics of rub-induced rotor response, initial conditions, as well as appropriate ranges of system parameters. Of special interest are the changes in the apparent nonlinearity of the system dynamics as rubs are induced at different rotor speeds. In particular, starting with 2nd order …