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Full-Text Articles in Physics

Ultrasonic System Models And Measurements , Ana Lilia Lopez-Sanchez Jan 2005

Ultrasonic System Models And Measurements , Ana Lilia Lopez-Sanchez

Retrospective Theses and Dissertations

In this work ultrasonic models and measurements are used to characterize a number of the important elements of an ultrasonic measurement system as well as the entire system. Ultrasonic measurement models for predicting the response from reference reflectors are described, including a new ultrasonic measurement model recently developed to simulate the ultrasonic response of an infinitely long cylindrical cavity. The reference reflectors considered include spherical pores, flat-bottom holes and side-drilled holes, which are commonly used in nondestructive evaluation studies. These reflectors are employed in a series of modeling/experimental studies to assess where approximate and more exact scattering models are ...


Ultrasonic Guided Waves In Composite Plates: A Study Of Interface Bond Condition And Material Properties Determination With Broadband Focused Air-Coupled Ultrasounds , Sorin Vasile Teles Jan 2004

Ultrasonic Guided Waves In Composite Plates: A Study Of Interface Bond Condition And Material Properties Determination With Broadband Focused Air-Coupled Ultrasounds , Sorin Vasile Teles

Retrospective Theses and Dissertations

This work is focused on two important aspects of the study of the composite materials: characterization of interface bonding in layered composites and evaluation of elastic material properties in air-coupled experiments.;The characterization of interface condition in a layered composite is critical to understand the behavior of the material under various stress situations. A closed disbond, alternatively known as zero-volume disbond or " kissing-disbond" (KSD) is difficult to detection by conventional normal-incidence ultrasonic nondestructive evaluation (NDE) methods. Such undetected defect may be dangerous because it can produce a significant decrease in structural integrity or lead to a catastrophic failure under certain ...


Development And Modeling Of Iron-Gallium Alloys , Rick Allen Kellogg Jan 2003

Development And Modeling Of Iron-Gallium Alloys , Rick Allen Kellogg

Retrospective Theses and Dissertations

Alloys of iron substituted with non-magnetic gallium (Galfenol) appear promising as mechanically robust actuator/sensing materials. They offer desirable properties including tensile strengths and magnetostrictive strains, respectively, on the order of 100 MPa and 100 x 10-6. To advance the understanding of these materials, this dissertation examines the alloys' magnetic and mechanical response as a function of applied magnetic field, mechanical stress, temperature, stoichiometry and crystallographic morphology. Characterizations of the alloys' single-crystal magneto strictive, elastic and plastic properties are used to facilitate the development and modeling of polycrystalline forms of the material having preferred crystallographic orientations (i.e. texture). The ...


Effects Of Material Microstructure And Surface Geometry On Ultrasonic Scattering And Flaw Detection , Yanming Guo Jan 2003

Effects Of Material Microstructure And Surface Geometry On Ultrasonic Scattering And Flaw Detection , Yanming Guo

Retrospective Theses and Dissertations

This dissertation studies the effect of two practical attributes of structural materials on ultrasonic inspection. The effects of the material microstructure of polycrystalline aluminum alloys on propagating ultrasonic waves and the effects of surface curvature and roughness on ultrasonic scattering and flaw detectability are both addressed.;The relationships between ultrasonic properties (velocity, attenuation, and backscattering) and the microstructure are studied both experimentally and theoretically for rolled aluminum samples with highly elongated grains. Attenuation measurements show a very small anisotropy, whereas backscattering measurements show a very high anisotropy. Existing theories and related extensions are able to explain these physical phenomena. Three ...


Electromechanical Characterization Of Ultrasonic Nde Systems , Changjiu Dang Jan 2001

Electromechanical Characterization Of Ultrasonic Nde Systems , Changjiu Dang

Retrospective Theses and Dissertations

An ultrasonic nondestructive evaluation (NDE) measurement system is a complex collection of many elements such as the pulser/receiver, the cabling, the transducers, and the material configuration being tested. To completely model an ultrasonic measurement system, a system model, called the electroacoustic measurement (EAM) model , was developed. This model allows one to analyze the measurement system at many different levels, ranging from individual details to the entire system itself. The EAM model has been implemented in software using the MATLAB development environment such that one has control over the specification of the detailed system components. On the other hand, the ...


Ultrasonic Beam Models In Anisotropic Media , Matthias Rudolph Jan 1999

Ultrasonic Beam Models In Anisotropic Media , Matthias Rudolph

Retrospective Theses and Dissertations

This dissertation models the sound fields produced by ultrasonic transducers for immersion inspections where the sound fields pass through general curved interfaces into a general anisotropic material;The foundations for these models are discussed, including slowness surfaces for anisotropic materials and the reflection/transmission of plane waves at a planar fluid/anisotropic solid interface;Three beam models are developed. Two of these models---the boundary diffraction wave model and the multi-Gaussian model---rely on the paraxial approximation, resulting in models that are computationally very efficient. As a consequence, those models can be used to conduct parametric studies in a highly effective manner ...


Nonlinear And Hysteretic Magnetomechanical Model For Magnetostrictive Transducers , Marcelo Jorge Dapino Jan 1999

Nonlinear And Hysteretic Magnetomechanical Model For Magnetostrictive Transducers , Marcelo Jorge Dapino

Retrospective Theses and Dissertations

The growing interest on magnetostrictive materials for generation of strains and forces in smart structure systems motivates the development of increasingly accurate models of the performance of these materials as used in transducers. The proposed magnetomechanical model provides a characterization of the material magnetization as well as the strain and force output by a transducer in response to quasistatic applied magnetic fields. The model is built in three steps. In the first, the mean field model for ferromagnetic hysteresis originally developed by Jiles and Atherton is used to compute the magnetization arising from the application of magnetic fields. While this ...


Interaction Of Acoustic Beam With Elastic Structures , Han Zhang Jan 1997

Interaction Of Acoustic Beam With Elastic Structures , Han Zhang

Retrospective Theses and Dissertations

This thesis describes experiments and calculations performed on the interaction of acoustic beams in water and air with planar and cylindrical elastic structures. Ultrasonic reflection measurements have been used to elucidate the phenomena of guided wave generation and reradiation by selecting beam incidence at, or near, phase-matching conditions. Under these circumstances reasonant mode conversion of accoustic wave to guided wave mode energy can occur. This interaction has been studied in rubber-coated steel, aluminum, plexiglas, and graphite-epoxy composite. The acoustic coupling media used in these experiments has been either water or air;Some theoretical modeling has also been undertaken to explain ...


Design, Analysis, And Modeling Of Giant Magnetostrictuve Transducers , Frederick Theodore Calkins Jan 1997

Design, Analysis, And Modeling Of Giant Magnetostrictuve Transducers , Frederick Theodore Calkins

Retrospective Theses and Dissertations

The increased use of giant magnetostrictive, Terfenol-D transducers in a wide variety of applications has led to a need for greater understanding of the materials performance. This dissertation attempts to add to the Terfenol-D transducer body of knowledge by providing an in-depth analysis and modeling of an experimental transducer. A description of the magnetostriction process related to Terfenol-D includes a discussion of material properties, production methods, and the effect of mechanical stress, magnetization, and temperature on the material performance. The understanding of the Terfenol-D material performance provides the basis for an analysis of the performance of a Terfenol-D transducer. Issues ...


The Effect Of Rib Attachment Properties On Structural Acoustics , Matthew Scott Carney Jan 1996

The Effect Of Rib Attachment Properties On Structural Acoustics , Matthew Scott Carney

Retrospective Theses and Dissertations

Sound Pressure measurements were taken of several 2.44m long thin beams which had 0.635cm wide t-ribs centered on them. The beams were excited by a chirp signal with the frequency range of 500Hz to 1500Hz. Two rib attachment methods were used on the beams. One group of beams were machined out of thick stock to the geometry of a rib welded to a beam to ensure that the rib and attachment were one continuous media. The other group of beams had ribs that were welded on. Fillets from the welding process were subjected to heat-treatment and machining to ...


Ultrasonic Transducer Characterization And Transducer Beam Modeling For Applications In Nondestructive Evaluation , Terence Peter Lerch Jan 1996

Ultrasonic Transducer Characterization And Transducer Beam Modeling For Applications In Nondestructive Evaluation , Terence Peter Lerch

Retrospective Theses and Dissertations

In this work, analytic models have been developed for two different nondestructive evaluation (NDE) applications: the characterization of spherically focused ultrasonic immersion transducers, and the prediction of the radiated wave fields of a variety of commonly used ultrasonic transducers;When a spherically focused probe is correctly and completely characterized, its corresponding theoretical model can accurately predict the experimentally measured structure of its incident wave field. A new and efficient method for completely characterizing a spherically focused transducer and its accompanying measurement system is described. Predicted responses that make use of this method are shown to correspond very well to measured ...


Minimizing The Radiated Sound Power With Minimal Structural Modification , Daniel Henry Kruger Jan 1995

Minimizing The Radiated Sound Power With Minimal Structural Modification , Daniel Henry Kruger

Retrospective Theses and Dissertations

In cases where a structure's excitation cannot be altered, the sound radiation from the structure must be minimized by modifying the structure within given design constraints. This dissertation considers minimizing sound radiated by an existing structure with minimal changes to the structure itself. To accomplish this the sound power radiated by a structure was written as a function of the normal surface velocity using the boundary element method. The feasibility of reducing radiated sound power with small patches of constrained layer damping material is proved. Small patches of constrained layer damping material are placed on the structure to effectively ...


Active Noise Control In A Three-Dimensional Space , Jihe Yang Jan 1994

Active Noise Control In A Three-Dimensional Space , Jihe Yang

Retrospective Theses and Dissertations

In this research, a new approach is presented for optimizing the performance of active noise control in three-dimensional space. The work focuses on the critical role of determining the locations for secondary sources in active noise suppression. A systematic technique is proposed for estimating optimal locations of secondary sources on the boundary of a three-dimensional domain for both local and global active control of harmonic sound fields. The theoretical foundation of this work is Huygen's principle. The indirect boundary element method (IBEM) which is a numerical implementation of Huygen's principle is employed as a basis for the numerical ...


An Experimental Method For Structural Intensity And Source Location , Yong Zhang Jan 1993

An Experimental Method For Structural Intensity And Source Location , Yong Zhang

Retrospective Theses and Dissertations

This study investigates the structural intensity and the force distribution function as tools to study vibrating plates. A laser Doppler vibrometer is used in measuring the plate normal velocity for the calculation of the structural intensity and the force distribution function. Several examples show the possibility of locating sources and studying the influence of ribs and damping material attached to the plate surface;There have been many studies on structural intensity. This thesis shows that the differences between two commonly used formulations are the assumptions that are used in deriving the formulas;The force distribution function is introduced in this ...


Vibrational And Acoustic Response Of Ribbed Plates , Ten-Bin Juang Jan 1993

Vibrational And Acoustic Response Of Ribbed Plates , Ten-Bin Juang

Retrospective Theses and Dissertations

A self-consistent mathematical formulation, using the Fourier transform method and a direct Gaussian numerical integration scheme, is developed and verified for analysis of both vibrational and acoustic responses of infinite submerged ribbed plates. Further steps developed from standard theories make structural intensity, acoustic intensity, and acoustic power calculations possible in the nearfield and farfield, and are demonstrated in this work;The direct numerical integration scheme adopted to obtain responses has proved to be straightforward and reliable. Although the double integration expression in some responses makes the technique infeasible, a practical way to overcome that difficulty is demonstrated using a standard ...


Scattering Investigation Based On Acoustical Holography , Ming-Te Cheng Jan 1993

Scattering Investigation Based On Acoustical Holography , Ming-Te Cheng

Retrospective Theses and Dissertations

The objective of this research is to investigate sound scattering by an object using a two-surface measurement technique that separates the incident field and the scattered field. The separation technique is developed in cartesian and cylindrical coordinates. The decomposition method in the cartesian coordinate system is based on the principle that any wave form can be decomposed into plane-wave components by using a two dimensional spatial Fourier transform. For the cylindrical coordinate system, a two plane separation technique is based on decomposing the sound field into cylindrical waves. Numerical simulations are performed and the effect of various parameters are investigated ...


Determination Of Secondary Sources In Noise Cancellation With Boundary Element Method , Guang-Hann Chen Jan 1992

Determination Of Secondary Sources In Noise Cancellation With Boundary Element Method , Guang-Hann Chen

Retrospective Theses and Dissertations

The direct boundary element method is proposed in this thesis to solve acoustic radiation problems as well as to achieve regional noise cancellation in half space with uniform finite impedance over the surface. The boundary integral equation and half space Green's function were derived to accomplish these goals. Those formulations were verified by comparing numerical simulations with theoretical solutions as well as experimental results. In addition, the above formulations were extended to achieve regional noise cancellation in half space by applying the boundary element method;Two methods were investigated to obtain noise cancellation in desired regions. They are the ...


Solution Of Viscous Flow Problems By Using The Boundary Element Method , Abdel-Magid Abdel-Latif Abdalla Jan 1992

Solution Of Viscous Flow Problems By Using The Boundary Element Method , Abdel-Magid Abdel-Latif Abdalla

Retrospective Theses and Dissertations

A scheme based on the Boundary Element Method (BEM) for solving the problem of steady flow of an incompressible viscous fluid is presented in this thesis. The problem is governed by both Navier-Stokes (N-S) equations and the continuity equation. The fundamental solution of the two-dimensional N-S is derived, and the partial differential equations are converted to an integral equation;The computer code is flexible enough to handle a variety of boundary and domain elements with different degrees of interpolation polynomial. Boundary and domain integrals over corresponding elements are evaluated analytically. The Newton Raphson iteration scheme accompanied by a relaxation factor ...


Application Of The Boundary Element Method To Elastic Wave Scattering Problems In Ultrasonic Nondestructive Evaluation , Paul Jay Schafbuch Jan 1991

Application Of The Boundary Element Method To Elastic Wave Scattering Problems In Ultrasonic Nondestructive Evaluation , Paul Jay Schafbuch

Retrospective Theses and Dissertations

The boundary element method (BEM) is used to numerically simulate the interaction of ultrasonic waves with material defects such as voids, inclusions, and open cracks. The time harmonic formulation is in 3D and therefore allows flaws of arbitrary shape to be modeled. The BEM makes such problems feasible because the underlying boundary integral equation only requires a surface (2D) integration and difficulties associated with the seemingly infinite extent of the host domain are not encountered. The computer code utilized in this work is built upon recent advances in elastodynamic boundary element theory such as a scheme for self adjusting integration ...


Application Of Ultrasonic Guided Waves To The Characterization Of Texture In Metal Sheets Of Cubic And Hexagonal Crystallites , Yan Li Jan 1990

Application Of Ultrasonic Guided Waves To The Characterization Of Texture In Metal Sheets Of Cubic And Hexagonal Crystallites , Yan Li

Retrospective Theses and Dissertations

Texture (preferred grain orientation) of polycrystalline metal sheets is an important material property which influences the process of making products such as aluminum cans and automobile and aircraft components. Traditionally, the texture is determined by X-ray or neutron diffraction techniques which are often destructive and time-consuming in nature. Over the last decade, ultrasonics has been found to provide an alternative way to characterize texture nondestructively and quickly. This dissertation makes an in-depth study of the fundamental physical principles of ultrasonic characterization of texture in metal sheets of cubic and hexagonal crystallites. The foundation is laid by investigations of wave propagation ...


Modeling Of Ultrasonic Scattering Experiments With Applications To System And Transducer Characterization , David Duane Bennink Jan 1990

Modeling Of Ultrasonic Scattering Experiments With Applications To System And Transducer Characterization , David Duane Bennink

Retrospective Theses and Dissertations

The voltage signal output by the receiver electronics, which represents the observable quantity in an ultrasonic scattering experiment, is written as a product, in the frequency domain, of two factors: the system efficiency and the scattering coefficient. The system efficiency represents the combined electrical properties of both the generator and receiver electronics and is a function of frequency only. The scattering coefficient represents the acoustic nature of the experiment (the radiation, propagation, scattering and reception of ultrasonic waves) and depends on the distributed field properties of the transducers involved and their locations and orientations, on the number and type of ...


Acoustic Finite Element Analysis Of Duct Boundaries , Robert James Bernhard Jan 1982

Acoustic Finite Element Analysis Of Duct Boundaries , Robert James Bernhard

Retrospective Theses and Dissertations

The finite element method has been found to be useful for problems in acoustics. The method as presently applied is not efficient for several common acoustic geometries. This dissertation investigates problems associated with applying the finite element method to acoustic geometries with repeated or standard features and to geometries involving open boundary segments;Substructuring methods are modified and applied to problems involving internal acoustic propagation. It is found that substructuring can be usefully applied for transient response analysis, for frequency response analysis, for repeated geometries, and for parametric studies. Sub-structuring techniques are shown to be an inefficient substitute for higher ...