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Full-Text Articles in Engineering Science and Materials

Influence Of Anisotropy On The Dispersion Characteristics Of Guided Ultrasonic Plate Modes, Yan Li, R. Bruce Thompson May 1990

Influence Of Anisotropy On The Dispersion Characteristics Of Guided Ultrasonic Plate Modes, Yan Li, R. Bruce Thompson

Ames Laboratory Publications

Dispersion curves are developed for elastic wave propagation in an anisotropic plate of monoclinic or higher symmetry. Emphasis is placed on analytic expressions for various features. Generalization of the isotropic Rayleigh–Lamb dispersion relations are derived for the cases of (a) propagation along a material symmetry axis and (b) propagation in a general direction. Examination of the high‐frequency limit of the lowest symmetric and antisymmetric mode dispersion curves yields expressions for the half‐space surface or Rayleigh wave velocity. It is shown that the dispersion curves for these modes can exhibit multiple crossings in approaching this limit, and an ...


Acoustic Properties Of Soybeans, Manjit K. Misra, B. Koerner, A. Pate, C. P. Burger Mar 1990

Acoustic Properties Of Soybeans, Manjit K. Misra, B. Koerner, A. Pate, C. P. Burger

Agricultural and Biosystems Engineering Publications

Acoustic transmission and impact force response methods were investigated for classification of soybeans. The transmission method was slow and not suitable for real-time application. A polynomial was fitted to the deconvolved frequency spectrum of acoustic impulse data for soybeans. The curve fitting procedure successfully predicted the mass of each soybean. The size of soybeans was related to the bandwidth. Diseased soybeans consistently showed narrower bandwidths than healthy soybeans. The diseased and damaged soybeans had broad variations in low frequency which was quantifiable by threshholding the error of fit in the curve fitting procedure.


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.


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 ...


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 ...


Interactive Diffraction Of A Plane Longitudinal Wave By A Pair Of Coplanar Central Cracks In An Elastic Solid, Y. M. Tsai Jan 1987

Interactive Diffraction Of A Plane Longitudinal Wave By A Pair Of Coplanar Central Cracks In An Elastic Solid, Y. M. Tsai

Review of Progress in Quantitative Nondestructive Evaluation

The problem of the diffraction of a plane longitudinal wave by a penny-shaped crack has been solved using the techniques of Hankel transforms [1]. The interaction of elastic waves with a Griffith crack has been investigated for a range of values of the wave frequency [2]. More recently, approximate formulas have been derived for the problem of diffraction of elastic waves by two coplanar Griffith cracks in an infinite elastic medium [3].


The Clamping Force Of Heat Shrinkable Fittings, David K. Rehbein, B. J. Skillings, J. F. Smith, Donald O. Thompson Jan 1983

The Clamping Force Of Heat Shrinkable Fittings, David K. Rehbein, B. J. Skillings, J. F. Smith, Donald O. Thompson

Review of Progress in Quantitative Nondestructive Evaluation

A number of alloys exhibit a phenomenon which has come to be known as ‘shape memory’. Without exception these alloys undergo a rather special type of martensitic transformation which results from one or another of the elastic constants1–7 weakening with changing temperature to the point that at the transformation temperature the transforming phase becomes both mechanically and thermodynamically unstable. ‘Shape memory’ is exhibited in the following way. A specimen at a temperature above the martensitic transformation is shaped to some desired form. The specimen is then cooled below its transformation temperature and deformed. Subsequent heating of the specimen through ...