Acoustics, Dynamics, and Controls Commons^™

Dynamics And Steering Of A Vibration-Driven Bristle Bot In A Pipe System, Ian Stewart

All Theses

Soft vibrational robots are robots that incorporate compliant structures into their design and are driven by oscillating actuators. A recent, popular version of a soft vibrational robot is the bristle bot, which uses flexible bristles and a vibration motor to propel itself across surfaces and through pipes. This motion is primarily driven by stick-slip dynamics resulting from asymmetric frictional forces applied at the bristle tips. Depending on the frequency of vibration of the motor, the robot experiences various resonance regions allowing it to maneuver in different directions. Attaching bristles to all sides of the robot and placing it in a …

Alternative Method For Low Frequency Impact Sound Measurement For Building Field Tests, Sunit Girdhar

Dissertations, Master's Theses and Master's Reports

What do high heels, dog nails, and dragging furniture have in common? They are all frequent sources of noise pollution and annoyance in multi-story buildings. Building codes exist to control and mitigate such noise, but these codes are outdated and fail to protect the residents against noise annoyance. Footstep noise is still the number one cause of complaints among the residents. The impact performance of floor-ceiling assemblies is characterized using a single-number rating called the Impact Sound Rating (ISR). A standard tapping machine is used in pre-defined locations on the floor and the radiated Sound Pressure Level (SPL) is measured …

Evaluating The Effects Of Granulated Rubber And Glass Fibers In Polymer Concrete As A Structural Material For Wafer Grinding Machines, Kevin Gabriel Kuehn, Philip Randall Streeter

Materials Engineering

Polymer concrete is a composite material used to replace cast iron and steel in wafer grinding machines for vibration damping. During the grinding and lapping processes of manufacturing silicon wafers, excessive vibrations may cause subsurface damage which requires additional polishing and reduces yield. Nine compositions containing various levels of granulated rubber and glass fibers were manufactured. CRM WRF-10 granulated rubber was examined at 0%, 5%, and 10% and Corning Cem-Fil glass fibers were added at 0%, 0.5%, and 1% by weight. Smooth-On EpoxAcast 690 epoxy resin was held constant at 16% for each composition. Crushed granite aggregate from Martin Marietta, …

Mtb Daq - Mountain Bike Data Acquisition System, Theodore J. Philliber, Ronan M. Shaffer, Dylan M. Ruiz, John M. Ringrose

Mechanical Engineering

Mountain bike suspensions systems are set up and tuned based only on qualitative, ‘feeling’-based metrics. The MTB DAQ, sponsored by Dr. Joseph Mello with the Cal Poly Mechanical Engineering Department, is a data acquisition system we developed to improve suspension tuning with a data-driven approach. The system mounts to a bicycle frame and has sensors that measure vibration and travel speed to characterize the bike’s motion. While similar systems exist, they cost in the thousands of dollars range and are very specific to individual bike geometry. Our system was designed to be more affordable to the average rider as well …

Understanding The Nonlinear Dynamics Governing Vertical-Lift Vehicles With Variable-Speed, Fixed Rotors, Stephanie Vavra, Micah Busboom, Aleea Stanford, Keegan Moore

UNL Student Research Days Posters, Undergraduate

Problem: Traffic significantly limits travel in urban areas. • The NASA Urban Air Mobility Project is developing an air taxi as an alternative mean of transportation (Fig. 1).

Challenge: Operating rotors at different frequencies may cause the cabin to vibrate at high amplitudes. Such effects are currently unknown.

Objective: Understand the effect of variable speed rotors on passenger comfort.

From the reduced-order modeling simulations, it can be assumed that counteracting the rotor speed in-balances can reduce the displacement and vibrations experienced at the center of the wing. In other words, should a rotor not maintain its optimal operation speed, reducing …

Vibration Isolation System, Bradley Y. Kwan, Bailey Groh, Max Wu, Nicole Yen

Mechanical Engineering

The Vibration Isolation System Senior Project is a collaborative group project between its sponsor, Maxar Technologies, and a team of students from Cal Poly - SLO to effectively design, manufacture, and test a structural assembly for satellites, isolating vibrations during launch and orbit conditions. After initial sponsor contact, requirements and needs were set which dictated deliverables for the senior project group. The group performed analyses to validate all design decisions, including a modified concept and design direction, selection of a prototype viscoelastic damping material, preliminary testing to validate design specifications, and detailed design and analysis toward a finalized design. Instead …

Improved Low-Frequency Impact Insulation Class Measurements Based On Comparison Techniques, Sunit Girdhar

Dissertations, Master's Theses and Master's Reports

In today’s world, noise pollution is growing as a major concern and it is becoming more and more difficult to find quiet places. But when the problem escalates to the extent that people are annoyed with loud noises even in their apartments, it becomes an alarming issue for engineers. Around the world, cities have defined some basic performance requirements for buildings, and isolation of residents from noise is one of the cardinal performance requirements. In the United States, building codes use the Impact Insulation Class (IIC) rating to characterize the performance of floor/ceiling assemblies. This method uses the response measured …

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 …

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 …

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 …

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 …

Characterization Of Conducting-Polymer-Based Bimorph Vibration Sensors, Weihua Li, Geoffrey M. Spinks, Lianbin Zhao, Yanzhe Wu, Dezhi Zhou, G G. Wallace

Professor Weihua Li

This paper presents theoretical and experimental investigation of mechanical-electrical properties of conducting polymers based bimorph sensors. A material parameter, hCP , is proposed to represent linear relationship between induction charge and the applied external deformation. Based on this assumption, a constitutive equation for bimorph sensors under steady-state external loadings are constructed and then solved. Mechanical-electrical properties of bimorph sensors are experimentally studied using both vibration-amplitude sweep mode and frequency sweep mode. The material parameter hCP , is identified by comparing theoretical analysis and experimental results. The applications of conducting polymers based bimorph sensors in smart structures are also discussed.

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: …

Vibration Reduction Of Offshore Wind Turbines Using Tuned Liquid Column Dampers, Colin Roderick

Masters Theses 1911 - February 2014

Offshore wind turbines (OWTs) are becoming an accepted method for generating electricity. The environmental conditions of offshore locations often impose high wind and wave forces on OWTs making them susceptible to intense loading and undesirable vibrations. One method to reduce system vibrations is through the use of structural control devices typically utilized in civil structures. Tuned liquid column dampers (TLCDs) show great promise in the application to OWTs due to their high performance and low cost. This thesis examines the use of TLCDs in OWTs.

Equations of motion for limited degree-of-freedom TLCD-turbine models are presented. A baseline analysis of each …

Method For Determination Of Complex Moduli Associated With Viscoelastic Material, Russell Scott Garner

Masters Theses

The aerospace industry is utilizing low cost miniature inertial measurement units (IMUs) that employ Micro Electro-Mechanical Systems (MEMS) technology in an effort to reduce size, weight, and cost of systems. A drawback of these MEMS devices is they are sensitive to vibration, shock and acoustic environments, which limits the usefulness of such devices in the severe environments imposed by many aerospace applications. In an effort to reduce the vibration, shock and acoustic environments experienced by these MEMS devices, the desire to develop passive damping treatments to structural components used to mount these devices. The damping treatments can be applied at …