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Articles 1 - 14 of 14

Full-Text Articles in Engineering Science and Materials

A Paraxial Theory For The Propagation Of Ultrasonic Beams In Anisotropic Solids, Byron P. Newberry, R. Bruce Thompson Jun 1989

A Paraxial Theory For The Propagation Of Ultrasonic Beams In Anisotropic Solids, Byron P. Newberry, R. Bruce Thompson

Center for Nondestructive Evaluation Publications

The necessity of nondestructively inspecting cast steels, weldments, composites, and other inherently anisotropic materials has stimulated considerable interest in wave propagation in anisotropic media. Here, the problem of an ultrasonic beam traveling in an anisotropic medium is formulated in terms of an angular spectrum of plane waves. Through the use of small angle approximations, the integral representation is reduced to a summation of Gauss–Hermite eigensolutions. The anisotropic effects of beam skew and excess beam divergence enter into the solution through parameters that are simply interpreted in terms of the slowness surface. Both time harmonic and pulsed solutions are discussed ...


Reciprocity-Based Measurement Models For Ultrasonic Nde, David D. Bennink, Anna L. Pate Jan 1989

Reciprocity-Based Measurement Models For Ultrasonic Nde, David D. Bennink, Anna L. Pate

Review of Progress in Quantitative Nondestructive Evaluation

Quantitative NDE objectives such as the evaluation of flaw signals and the assessment of inspection capabilities generate the need for models of ultrasonic scattering measurements capable of including all aspects of the measurement process: radiation and reception characteristics of probes, propagation of finite beams, scattering of nonplane-wave fields, and the like. Once such models are developed and validated, that is, proven able to predict the received voltages obtained in actual ultrasonic experiments, they can be used to gain a thorough understanding of the NDE inspection process. Specifically, these models will be useful in investigations of the factors that significantly affect ...


Ultrasonic Transducer Calibration For Reciprocity-Based Measurement Models, David D. Bennink, Anna L. Pate Jan 1989

Ultrasonic Transducer Calibration For Reciprocity-Based Measurement Models, David D. Bennink, Anna L. Pate

Review of Progress in Quantitative Nondestructive Evaluation

A general formulation regarding the relationship between scatterer properties and experimental signals was presented in a companion paper[1]. This formulation was developed for the case of acoustic wave scattering in an immersion measurement. In order to perform the theoretical calculations, the formulation requires knowledge of the radiation and reception characteristics of the probes involved and the combined properties of the pulser and the receiver (system efficiency). Thus, the objective of this paper is to discuss methods for obtaining the characteristics of measurement systems as required in the above-mentioned formulation. As an example, the case of acoustic wave scattering from ...


3-D Ultrasonic Scattering By Surface-Breaking Cracks, D. E. Budreck, J. D. Achenbach Jan 1989

3-D Ultrasonic Scattering By Surface-Breaking Cracks, D. E. Budreck, J. D. Achenbach

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic scattering by cracks which break the traction-free surface of an engineering structure is of considerable interest in the field of nondestructive evaluation, especially when the crack mouth is inaccessible to direct observation. Considerable effort has been expended in obtaining solutions to the two-dimensional problem, from which much has been learned. A representative cross-section of work on the two-dimensional problem includes papers by Mendelsohn, et al. [1], Achenbach and Norris [2], Datta and Shah [3], Zhang and Achenbach [4], and Roberts [5]. However, if the crack dimensions are comparable to the width of the interrogating ultrasonic beam, the full three-dimensional ...


Hypersingular Integral Equations For Crack Problems, G. Krishnasamy, Lester W. Schmerr Jr., Thomas J. Rudolphi, F. J. Rizzo Jan 1989

Hypersingular Integral Equations For Crack Problems, G. Krishnasamy, Lester W. Schmerr Jr., Thomas J. Rudolphi, F. J. Rizzo

Review of Progress in Quantitative Nondestructive Evaluation

The investigation of scattering of waves by cracks in an elastic medium and by thin scatterers in an acoustic medium, via analytical and experimental methods, seems to be of continuing importance to nondestructive evaluation. On the analytical side, formulation and numerical solution of crack scattering problems using boundary integral equations is popular and effective because of the very nature of a crack, but this approach still suffers some shortcomings of an analytical nature. That is, the governing equations in their primitive form involve a hypersingular kernel function, and the usual process of regularization to lower the kernel singularity usually introduces ...


The Scattering Response Of A Flat-Bottom Hole, Lester W. Schmerr Jr., Alexander Sedov Jan 1989

The Scattering Response Of A Flat-Bottom Hole, Lester W. Schmerr Jr., Alexander Sedov

Review of Progress in Quantitative Nondestructive Evaluation

The flat-bottom hole is one of the oldest reference/calibration standards in the field of ultrasonic nondestructive evaluation (NDE). It has been used for both calibration of ultrasonic test equipment sensitivity and for the generation of distance-amplitude correction (DAC) curves [1]. Flat-bottom holes are also useful for equivalent flaw sizing applications since they can represent the response, at normal incidence, of ideal “perfect” scatterers, such as flat cracks.


A Generalized Eigenfunction Expansion For Elastodynamics, David E. Budreck, James H. Rose Jan 1989

A Generalized Eigenfunction Expansion For Elastodynamics, David E. Budreck, James H. Rose

Review of Progress in Quantitative Nondestructive Evaluation

The use of composite materials in structural components is limited, in part, by the need to develop quantitative inspection techniques. Composites present many challenges to the development of such quantitative methods. For example, composite materials are typically anisotropic. Thus a necessary prerequisite for ultrasonic flaw detection and characterization in composite materials is an understanding of the propagation and scattering of waves in a general anisotropic media. Work towards such an understanding has been typically limited to such issues as beam propagation effects (see, for ex., Ref. [1]). The elastic wave inverse scattering problem (flaw characterization), as well as the simpler ...


Free Wave Propagation In Plates Of General Anisotropic Media, Adrian H. Nayfeh, Dale E. Chimenti Jan 1989

Free Wave Propagation In Plates Of General Anisotropic Media, Adrian H. Nayfeh, Dale E. Chimenti

Review of Progress in Quantitative Nondestructive Evaluation

The propagation of Lamb waves in plates has been the subject of numerous investigations since their postulation by Lamb in 1916 [1,2]. Most of the work in existence deals with various aspects of these guided waves in plates of isotropic materials. Comparatively speaking a limited number of results has appeared in which Lamb or horizontaly polarized SH wave propagation in anisotropic plates has been considered in any detail. For Lamb waves, theoretical analyses have been reported in plates of cubic [3,4], transversely isotropic [5,6], and orthotropic [7,9] media.


Propagation Of Guided Elastic Waves In Orthotropic Plates, Y. Li, R. Bruce Thompson Jan 1989

Propagation Of Guided Elastic Waves In Orthotropic Plates, Y. Li, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

Numerical studies of wave propagation in free anisotropic plates were conducted at Stanford University in the early 70’s [1,2], followed by a flurry of related work. Yet, this subject has not been completely understood. Recent years, however, have seen greatly increased interests in the influence of the anisotropy of composites and textured metal plates on Lamb wave propagation characteristics. This paper presents the basic theory for the propagation of guided elastic waves in orthotropic plates. Included are both numerical results and analytical or semianalytical expressions for the generalized Rayleigh-Lamb dispersion equations. As examples, comparisons are made of the ...


Deformation Of Leaky Lamb Wave Spectrum In Fluid-Loaded Plates, S. I. Rokhlin, Dale E. Chimenti, A. H. Nayfeh Jan 1989

Deformation Of Leaky Lamb Wave Spectrum In Fluid-Loaded Plates, S. I. Rokhlin, Dale E. Chimenti, A. H. Nayfeh

Review of Progress in Quantitative Nondestructive Evaluation

If an elastic layer is loaded by an ideal liquid the propagation of Lamb waves will be accompanied by radiation of energy into the liquid if the phase velocity of these waves exceeds the sound velocity in the liquid. For this reason Lamb waves in a plate loaded by a liquid are called “leaky Lamb waves”, and we adopt this terminology.


Ultrasonic Reflection And Wave Propagation In Multilayered Composite Plates, Dale E. Chimenti, Adrian H. Nayfeh Jan 1989

Ultrasonic Reflection And Wave Propagation In Multilayered Composite Plates, Dale E. Chimenti, Adrian H. Nayfeh

Review of Progress in Quantitative Nondestructive Evaluation

This paper presents selected results of numerous ultrasonic reflection measurements on plates of laminated composites in which the angle of incidence of the acoustic wave and its frequency have been varied. These measurements have been carried out on biaxially laminated graphite-epoxy specimens utilizing water as a fluid coupling medium. The stacking sequence of the samples investigated is restricted to the case of 0–90° lamination. The data are compared to the results of a recent theoretical analysis based on an exact analytical treatment of wave propagation in a fluid-coupled orthotropic plate in conjunction with a transfer matrix approach. Reflection and ...


Elastic Wave Scattering By Arbitrarily Shaped Voids, Paul J. Schafbuch`, R. Bruce Thompson, F. J. Rizzo, Thomas J. Rudolphi Jan 1989

Elastic Wave Scattering By Arbitrarily Shaped Voids, Paul J. Schafbuch`, R. Bruce Thompson, F. J. Rizzo, Thomas J. Rudolphi

Review of Progress in Quantitative Nondestructive Evaluation

This work is motivated by the need for realistic ultrasonic probability of detection (POD) models in nondestructive evaluation (NDE). Past POD models have utilized flaw farfield scattering amplitudes along with other system parameters to predict the expected signal in postulated measurement geometries [1]. However, numerical evaluations of scattering amplitudes have generally been restricted to idealized flaw shapes and, to our knowledge, no scheme to calculate scattering amplitudes of arbitrary shape has ever been implemented in 3D. Volumetric shapes with an axis of symmetry have been examined with T-matrix and MOOT [2,3] but the axisyrametric limitation precludes a large portion ...


Transducer Effects On Ultrasonic Attenuation Measurements, Mary A. Paul Jan 1989

Transducer Effects On Ultrasonic Attenuation Measurements, Mary A. Paul

Retrospective Theses and Dissertations

Ultrasonic nondestructive evaluation can be used to quantitatively interpret received electrical signals from ultrasonic measurements. In order to preform this interpretation, several techniques have been used. Two of these techniques are the standard procedure and the measurement model. The standard procedure compares the waves reflected from the flawed specimen with the waves reflected from many specimens of the same host material with different known flaws in the interior. By matching reflections, the approximate size of the flaw can be estimated by comparison with the response from the known standard flaw model; however, this method requires a large number of known ...


Ultrasonic Nondestructive Evaluation Of Impact-Damaged Thermoset And Thermoplastic Composite Laminates, Brad Lucht Jan 1989

Ultrasonic Nondestructive Evaluation Of Impact-Damaged Thermoset And Thermoplastic Composite Laminates, Brad Lucht

Retrospective Theses and Dissertations

The aerospace industry, driven by a demand to reduce weight, has relied increasingly on composite materials to increase performance of advanced systems. However, impacts by foreign objects such as runway debris can damage composite components without leaving indentations or other visually identifiable marks. Microcracking of the matrix, fiber pullout, and delaminations are among the types of resultant internal damage that can weaken the structure and affect the ultimate load strength as well as fatigue life. The field of nondestructive evaluation (NDE) provides a means for the detection and evaluation of barely visible impact damage. In this study glass/epoxy, carbon ...