Open Access. Powered by Scholars. Published by Universities.®
Acoustics, Dynamics, and Controls Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 13 of 13
Full-Text Articles in Acoustics, Dynamics, and Controls
Use Of Pattern Classification Algorithms To Interpret Passive And Active Data Streams From A Walking-Speed Robotic Sensor Platform, Eric Allen Dieckman
Use Of Pattern Classification Algorithms To Interpret Passive And Active Data Streams From A Walking-Speed Robotic Sensor Platform, Eric Allen Dieckman
Dissertations, Theses, and Masters Projects
In order to perform useful tasks for us, robots must have the ability to notice, recognize, and respond to objects and events in their environment. This requires the acquisition and synthesis of information from a variety of sensors. Here we investigate the performance of a number of sensor modalities in an unstructured outdoor environment, including the Microsoft Kinect, thermal infrared camera, and coffee can radar. Special attention is given to acoustic echolocation measurements of approaching vehicles, where an acoustic parametric array propagates an audible signal to the oncoming target and the Kinect microphone array records the reflected backscattered signal. Although …
Investigation Of Ultrasonic Wave Scattering Effects Using Computational Methods, Cara Ann Campbell Leckey
Investigation Of Ultrasonic Wave Scattering Effects Using Computational Methods, Cara Ann Campbell Leckey
Dissertations, Theses, and Masters Projects
Advances in computational power and expanded access to computing clusters has made mathematical modeling of complex wave effects possible. We have used multi-core and cluster computing to implement analytical and numerical models of ultrasonic wave scattering in fluid and solid media (acoustic and elastic waves). We begin by implementing complicated analytical equations that describe the force upon spheres immersed in inviscid and viscous fluids due to an incident plane wave. Two real-world applications of acoustic force upon spheres are investigated using the mathematical formulations: emboli removal from cardiopulmonary bypass circuits using traveling waves and the micromanipulation of algal cells with …
Applications Of Pattern Classification To Time-Domain Signals, Crystal Ann Bertoncini
Applications Of Pattern Classification To Time-Domain Signals, Crystal Ann Bertoncini
Dissertations, Theses, and Masters Projects
Many different kinds of physics are used in sensors that produce time-domain signals, such as ultrasonics, acoustics, seismology, and electromagnetics. The waveforms generated by these sensors are used to measure events or detect flaws in applications ranging from industrial to medical and defense-related domains. Interpreting the signals is challenging because of the complicated physics of the interaction of the fields with the materials and structures under study. often the method of interpreting the signal varies by the application, but automatic detection of events in signals is always useful in order to attain results quickly with less human error. One method …
Ultrasonic Guided Wave Interpretation For Structural Health Inspections, Jill Paisley Bingham
Ultrasonic Guided Wave Interpretation For Structural Health Inspections, Jill Paisley Bingham
Dissertations, Theses, and Masters Projects
Structural Health Management (SHM) combines the use of onboard sensors with artificial intelligence algorithms to automatically identify and monitor structural health issues. A fully integrated approach to SHM systems demands an understanding of the sensor output relative to the structure, along with sophisticated prognostic systems that automatically draw conclusions about structural integrity issues. Ultrasonic guided wave methods allow us to examine the interaction of multimode signals within key structural components. Since they propagate relatively long distances within plate- and shell-like structures, guided waves allow inspection of greater areas with fewer sensors, making this technique attractive for a variety of applications.;This …
Parallel Three-Dimensional Acoustic And Elastic Wave Simulation Methods With Applications In Nondestructive Evaluation, Kevin Edward Rudd
Parallel Three-Dimensional Acoustic And Elastic Wave Simulation Methods With Applications In Nondestructive Evaluation, Kevin Edward Rudd
Dissertations, Theses, and Masters Projects
In this dissertation, we present two parallelized 3D simulation techniques for three-dimensional acoustic and elastic wave propagation based on the finite integration technique. We demonstrate their usefulness in solving real-world problems with examples in the three very different areas of nondestructive evaluation, medical imaging, and security screening. More precisely, these include concealed weapons detection, periodontal ultrasography, and guided wave inspection of complex piping systems. We have employed these simulation methods to study complex wave phenomena and to develop and test a variety of signal processing and hardware configurations. Simulation results are compared to experimental measurements to confirm the accuracy of …
Sonar Sensor Interpretation For Ectogeneous Robots, Wen Gao
Sonar Sensor Interpretation For Ectogeneous Robots, Wen Gao
Dissertations, Theses, and Masters Projects
We have developed four generations of sonar scanning systems to automatically interpret surrounding environment. The first two are stationary 3D air-coupled ultrasound scanning systems and the last two are packaged as sensor heads for mobile robots. Template matching analysis is applied to distinguish simple indoor objects. It is conducted by comparing the tested echo with the reference echoes. Important features are then extracted and drawn in the phase plane. The computer then analyzes them and gives the best choices of the tested echoes automatically. For cylindrical objects outside, an algorithm has been presented to distinguish trees from smooth circular poles …
Ultrasonic Guided Wave Tomography Of Pipes: A Development Of New Techniques For The Nondestructive Evaluation Of Cylindrical Geometries And Guided Wave Multi-Mode Analysis, Kevin Raymond Leonard
Ultrasonic Guided Wave Tomography Of Pipes: A Development Of New Techniques For The Nondestructive Evaluation Of Cylindrical Geometries And Guided Wave Multi-Mode Analysis, Kevin Raymond Leonard
Dissertations, Theses, and Masters Projects
This dissertation concentrates on the development of two new tomographic techniques that enable wide-area inspection of pipe-like structures. By envisioning a pipe as a plate wrapped around upon itself, the previous Lamb Wave Tomography (LWT) techniques are adapted to cylindrical structures. Helical Ultrasound Tomography (HUT) uses Lamb-like guided wave modes transmitted and received by two circumferential arrays in a single crosshole geometry. Meridional Ultrasound Tomography (MUT) creates the same crosshole geometry with a linear array of transducers along the axis of the cylinder. However, even though these new scanning geometries are similar to plates, additional complexities arise because they are …
Theoretical And Experimental Study Of Generation Mechanisms For Laser Ultrasound In Woven Graphite /Epoxy Composites With Translaminar Stitching, Adam D. Friedman
Theoretical And Experimental Study Of Generation Mechanisms For Laser Ultrasound In Woven Graphite /Epoxy Composites With Translaminar Stitching, Adam D. Friedman
Dissertations, Theses, and Masters Projects
The aerospace industry is beginning to use advanced composite materials for primary load bearing structures and their failure mechanisms must be better understood to predict their behavior in service. The Combined Loads Tests (COLTS) facility is being constructed at the NASA Langley Research Center to characterize these failure mechanisms. Laser based ultrasonic NDE can monitor the samples during dynamic loading without interfering with the structural tests. However, the constraints of implementing laser ultrasound in a structures laboratory reduces the efficiency of the technique. The system has to be "eye-safe" because many people will be present during the structural tests. Consequently, …
Lamb Wave Diffraction Tomography, Eugene V. Malyarenko
Lamb Wave Diffraction Tomography, Eugene V. Malyarenko
Dissertations, Theses, and Masters Projects
As the worldwide aviation fleet continues to age, methods for accurately predicting the presence of structural flaws, such as hidden corrosion and disbonds, that compromise air worthiness become increasingly necessary. Ultrasonic guided waves, Lamb waves, allow large sections of aircraft structures to be rapidly inspected. However, extracting quantitative information from Lamb wave data has always involved highly trained personnel with a detailed knowledge of mechanical waveguide physics. In addition, human inspection process tends to be highly subjective, slow and prone to errors. The only practical alternative to traditional inspection routine is a software expert system capable of interpreting data with …
Propagation Of Rayleigh Waves In Thin Films, Agus A. Ananda
Propagation Of Rayleigh Waves In Thin Films, Agus A. Ananda
Dissertations, Theses, and Masters Projects
With the advent of thin film technology and more recently its applications in microelectronics and control of surface properties, the interest in mechanical properties of thin films has grown tremendously. Mechanical defects such as creep, fracture and adhesion loss, play a very important role in physical instabilities of thin film materials. An acoustic microscope has been built to study mechanical properties of thin-films. The microscope operates at a nominal frequency of 50 MHz. Rayleigh surface waves velocities on the surface of film-substrate systems were measured from V(z) curves generated by the acoustic microscope. V(z) curves are produced from interference between …
Propagation Of Guided Acoustic Waves In Composite Media, Michael David Seale
Propagation Of Guided Acoustic Waves In Composite Media, Michael David Seale
Dissertations, Theses, and Masters Projects
Composite materials are being more widely used today by aerospace, automotive, and a number of other commercial industries because of their advantages over conventional metals. Composites are finding applications ranging from bicycle frames to the proposed High-Speed Civil Transport (HSCT). Determining the response to a variety of damage mechanisms is necessary for a complete understanding of the total use environment of composite structures. The objective of the research presented here is to provide a method of quantifying the amount of damage in composite materials for a number of different damage scenarios. Components which have non-visible damage, but have degraded performance, …
Nonlinearity Parameters Of Polymers, Meng-Chou Wu
Nonlinearity Parameters Of Polymers, Meng-Chou Wu
Dissertations, Theses, and Masters Projects
Three types of acoustic nonlinearity parameters for solids are discussed. The results of measurements of these parameters for three polymers--polymethyl methacrylate, Polystyrene, and polysulfone--are presented.;The author has developed a new technique, using piezoelectric transducers directly bonded to the specimens, which allows the measurements of fundamental and second harmonics generated in the solids, and thereby the determination of nonlinearity parameter {dollar}\beta\sb3{dollar}, which is the ratio of a linear combination of second- and third-order elastic coefficients to the second-order elastic coefficient.;The second nonlinearity parameter, B/A can be determined from the temperature and pressure derivatives of the sound velocity. We derive its exact …
An Indicating Meter For Measuring Intensity Level Of Sound, Walter Sanders Foster
An Indicating Meter For Measuring Intensity Level Of Sound, Walter Sanders Foster
Dissertations, Theses, and Masters Projects
No abstract provided.