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Non-Collocated Vibration Suppression With Actively Controlled Resonant-Style Absorbers For Simultaneous Spectral And Spatial Tuning, Ryan Jenkins

Master's Theses

The research summarized in this work revisits the well-established actively-tuned vibration absorber concept from several unconventional angles. The first contribution involves an active tuning methodology of an absorber for spectral and spatial variations. The second is a set of generalized operating guidelines for such absorber tuning. "Spectral" tuning handles time-varying excitation frequencies, while "spatial" tuning treats the real-time variations in the desired location of suppression (an often-ignored dimension of vibration absorption research). Spatial tuning is inspired by the concept of “non-collocated vibration absorption”, for which the absorber location is different from the point of suppression.

The Delayed Resonator-based absorber, a …

Biomarkers Of Orthodontic Tooth Movement With Fixed Appliances And Vibration Appliance Therapy: A Randomized Clinical Trial, Stacey M. Reiss

Master's Theses

No abstract provided.

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 …

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 …

Effect Of Low Velocity Impact On The Vibrational Behavior Of A Composite Wing, Richard M. De Luna

Master's Theses

Impact strength is one of the most important structural properties for a designer to consider, but it is often the most difficult to quantify or measure. A major concern for composite structures in the field is the effect of foreign objects striking composites because the damage is often undetectable by visual inspection. The objective for this study was to determine the effectiveness of using dynamic testing to identify the existence of damage in a small scale composite wing design. Four different impact locations were tested with three specimens per location for a total of 12 wings manufactured. The different impact …

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 Effects Of Various Frequencies Of Low-Level Mechanical Vibration On Retention In An Orthodontic Relapse Model In Mice, Amir H. Assefnia

Master's Theses

ABSTRACT

Objectives: The aim of this study is to study the effect of mechanical vibration on retention following orthodontic tooth movement (OTM) in a mouse orthodontic relapse model. We applied various frequencies of vibration to the maxillary right first molar during relapse, and monitored changes to the alveolar bone and molar root.

Materials and Methods: Thirty-four male CD1 mice were placed in 4 groups. The Control Group underwent OTM for 7 days. The other three groups received OTM for 7 days, followed by a relapse phase of 7 days. OTM was performed with a 10g Ni-Ti spring. The Relapse Group …

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 …

Efficient Characterization Of Structural Dynamic Responses Under Uncertainties: From Order-Reduced Simulation To Data-Driven Emulation, Zeping Xia

Master's Theses

The efficiency of sampling remains as one of the major challenges for uncertainty analysis in structural dynamics. In the context of numerical experiments, this difficulty primarily lies in the fact that every single run of a numerical model, which usually is of large scale in modern engineering practice, would be expensive in terms of CPU times and memories. Nonetheless, understanding and predicting dynamic characteristics of structural systems with uncertainties is important for structural design, assessment and control. In order to develop fast and economical sampling techniques for characterizing structural dynamics, we explored two categories of methods from two opposite direction: …

The Effect Of A Low-Velocity Impact On The Flexural Strength And Dynamic Response Of Composite Sandwiches With Damage Arrestment Devices, Kodi A. Rider

Master's Theses

Impact strength is one of the most important structural properties for a designer to consider, but is often the most difficult to quantify or measure. A constant concern in the field of composites is the effect of foreign object impact damage because it is often undetectable by visual inspection. An impact can create interlaminar damage that often results in severe reductions in strength and instability of the structure. The main objective of this study is to determine the effectiveness of a damage arrestment device (DAD) on the mechanical behavior of composite sandwiches, following a low-velocity impact. A 7.56-lb_f crosshead …

Modal Analysis Of Composite Structures With Damping Material, Kellie Michelle Tremaine

Master's Theses

The purpose of this study is to develop an analytical solution for modal analysis of actively damped orthotropic composite plates in bending and to verify it with experimental analysis.

The analytical modal analysis solution for composite plate dynamics is derived using Euler theory. This analysis applies to structures with orthotropic lamina of uniform material properties at any lamination angle. The bending-extensional coupling can be neglected for plates that are symmetric or approximately symmetric, which allows an exact solution for natural frequency and mode shape to be obtained. An exact solution can be found for natural vibration and in general.

The …

Development And Application Of A Portable System To Reliably Measure Grip Forces Using Thin-Film Force Sensors, Shane Vincent Tornifoglio

Master's Theses

Accurate tracking of hand grip force is an important consideration needed for a robust understanding in the study of human biomechanics. One aspect where it proves useful is in hand-arm vibration, such as from gripping a power tool. Depending on how firmly the user is gripping the tool, they may change their exposure levels to the tool vibration, which can lead to potential disorders such as Hand-Arm Vibration Syndrome (HAVS).

A small, battery powered portable force unit has been developed to supply power to, and condition, the signals from eight thin-film force sensors. This gives a better understanding of the …

Second Generation Data-Logging System For Long-Duration Field Measurement Of Vibration Exposure And Grip Force, Robert H. Knapp Iii

Master's Theses

Millions of United States workers are exposed to vibration at their job, whether it is from a power tool that causes hand and arm vibration or from heavy machinery. These vibrations are known to result in physical disorders such as Hand-Arm Vibration Syndrome, which can be debilitating to the point where workers can no longer do their job effectively. Research groups have taken an interest in finding what vibration characteristics are most harmful and choose to record vibration information using data-logging devices. Often, many devices, whether they are commercial or custom-built devices, use frequency weightings and full day estimations to …