Open Access. Powered by Scholars. Published by Universities.^{®}

- Keyword

Articles **1** - **30** of ** 64**

## Full-Text Articles in Mechanical Engineering

Progress On Ultrasonic Flaw Sizing In Turbine Engine Rotor Components: Bore And Web Geometries, James H. Rose, T. A. Gray, R. Bruce Thompson, J. L. Opsal

#### Progress On Ultrasonic Flaw Sizing In Turbine Engine Rotor Components: Bore And Web Geometries, James H. Rose, T. A. Gray, R. Bruce Thompson, J. L. Opsal

*Review of Progress in Quantitative Nondestructive Evaluation*

The application of generic flaw sizing techniques to specific components generally involves difficulties associated with geometrical complexity and simplifications arising from a knowledge of the expected flaw distribution. This paper is concerned with the case of ultrasonic flaw sizing in turbine engine rotor components. The sizing of flat penny shaped cracks in the web geometry will be discussed and new crack sizing algorithms based on the Born and Kirchhoff approximations will be introduced. Additionally we propose a simple method for finding the size of a flat, penny shaped crack given only the magnitude of the scattering amplitude. The bore geometry ...

Crack Mapping By Ray Methods, J. D. Achenbach, A. N. Norris, L. Ahlberg, B. R. Tittmann

#### Crack Mapping By Ray Methods, J. D. Achenbach, A. N. Norris, L. Ahlberg, B. R. Tittmann

*Review of Progress in Quantitative Nondestructive Evaluation*

Two methods to map crack edges by the use of arrival times of edge-diffracted signals have been briefly reviewed. They are a global triangulation method and a local crack-edge mapping technique. The local mapping technique, which generally has the greater accuracy, has been applied to both synthetic and experimental data. The effect of a uniform error in the data has been investigated. The experimental data were obtained at the Rockwell International Science Center for a doorknob specimen with a plane crack of elliptical shape at its center. Crack mappings of very satisfactory accuracy were achieved.

Classification Of Nde Waveforms With Autoregressive Models, R. B. Melton

#### Classification Of Nde Waveforms With Autoregressive Models, R. B. Melton

*Review of Progress in Quantitative Nondestructive Evaluation*

This paper describes a new approach for classifying NDE waveforms. Using this approach a set of matched filters is constructed one for each category of waveform, based on parameters from autoregressive models. The method offers advantages in terms of hardware implementation over conventional pattern recognition approaches. Feasibility is shown using computer generated data. Results are then presented for real data from acoustic emission experiments.

Rough Surface Effects Of Aluminum Castings On Ultrasonic Sizing Algorithms, Kent Lewis, Dale Fitting, Laszlo Adler

#### Rough Surface Effects Of Aluminum Castings On Ultrasonic Sizing Algorithms, Kent Lewis, Dale Fitting, Laszlo Adler

*Review of Progress in Quantitative Nondestructive Evaluation*

Several techniques for characterizing flaws and inclusions using ultrasonic scattering information have been developed in recent years. These algorithms assume a noise-free medium and are sensitive to perturbations in the acquired spectra. However, surface roughness and volumetric porosity effects alter the available data.

In order to determine the effects of surface roughness typical of aluminum castings on inversion accuracy, a sequence of experiments was performed. Ultrasonic backscattering data were acquired from spheroidal defects in flat, smooth surfaced, diffusion bonded titanium samples. Next, the scattering spectra were perturbed using theoretically or experimentally determined transmission spectra obtained from rough surfaced cast aluminum ...

On The Effects Of A Finite Aperture On The Inverse Born Approximation, Vladimir G. Kogan, James H. Rose

#### On The Effects Of A Finite Aperture On The Inverse Born Approximation, Vladimir G. Kogan, James H. Rose

*Review of Progress in Quantitative Nondestructive Evaluation*

One of the most important effects of complex part geometry is that the available entrance and exit angles for ultrasound are limited. We will present a study of the Inverse Born Approximation in which we have data for incident (and exit) directions confined to a conical aperture. Modeling the direct problem by the Born Approximation, we obtained analytical results for (1) a weak spherical inclusion, and (2) a penny shaped crack (modeled by an oblate spheroid). General results are: (a) the value of the characteristic function γ is constant in the interior of the flaw, but reduced in value; (b ...

Eddy Current Characterization Of Applied And Residual Stresses, W. R. Junker, W. G. Clark Jr.

#### Eddy Current Characterization Of Applied And Residual Stresses, W. R. Junker, W. G. Clark Jr.

*Review of Progress in Quantitative Nondestructive Evaluation*

An exploratory investigation was conducted to evaluate the applicability of state-of-the-art eddy current nondestructive evaluation techniques to the characterization of applied and residual stresses in structural steels. Eddy current response versus stress measurements were developed for ASTM Type A533B and A471 steels under tensile, bending and residual stress loading conditions. A “shrink fit” specimen was used to establish applicability to residual stresses. Results show that an eddy current approach can be used to provide an accurate quantitative measure of surface stresses. The technique can also be used to map surface stress contours. Details of the procedure are described along with ...

Acoustoelasticity: Scanning With Shear Waves, N. Shaikh, C. Steele, G. S. Kino

#### Acoustoelasticity: Scanning With Shear Waves, N. Shaikh, C. Steele, G. S. Kino

*Review of Progress in Quantitative Nondestructive Evaluation*

Acoustoelasticity is a promising method for the in situ analysis of both applied and residual stresses. The object of this investigation is to establish a technique for scanned shear wave measurements so as to determine the individual components of an inhomogeneous stress state and their directions. A computer-controlled scanning system with a dry contact rubber backed transducer has been developed which provides complete automation of scanning and data reduction.

The theory of acoustoelasticity for anisotropic material has been developed using perturbation techniques. The experimental results on rolled aluminum plates confirm that, to a reasonable approximation, the effects of material anisotropy ...

The Effect Of Texture On Acoustoelasticity, George C. Johnson

#### The Effect Of Texture On Acoustoelasticity, George C. Johnson

*Review of Progress in Quantitative Nondestructive Evaluation*

The theory for stress determination using acoustoelasticity is most frequently based on the evaluation of the motion of an infinitesimal plane wave propagating through an isotropic, elastic body which is subjected to a homogeneous deformation. The assumption of isotropy in this analysis allows the characterization of the acoustoelastic response to be carried out in terms of two second-order and three third-order elastic constants. Unfortunately, most structural materials do not behave isotropically, but instead have some degree of texture caused by the crystals aligning themselves in certain preferred orientations during the forming process. This paper examines the effect of texture on ...

Residual Stress Characterization By Use Of Elastic Wave Scattering Measurements, E. Domany, J. E. Gubermatis

#### Residual Stress Characterization By Use Of Elastic Wave Scattering Measurements, E. Domany, J. E. Gubermatis

*Review of Progress in Quantitative Nondestructive Evaluation*

The presence of a state of residual stress in a material can impair its structural quality by adversely affecting its elastic limit, yield point, etc.1 Most common nondestructive measurements of residual stress use x-ray techniques.2 However, these techniques determine only the surface residual stresses, while in many practical cases knowledge of the bulk residual stresses is desired. Ultrasonic methods3,4 appear most natural for measuring bulk residual stress but are used infrequently, in part because of difficulty in adequately measuring small effects and in part because of the absence of theoretical results treating the inhomogeneous nature of residual ...

Absolute Determination Of Stress In Textured Materials, R. Bruce Thompson, John F. Smith, S. S. Lee

#### Absolute Determination Of Stress In Textured Materials, R. Bruce Thompson, John F. Smith, S. S. Lee

*Review of Progress in Quantitative Nondestructive Evaluation*

The continuum theory of elastic wave propagation in deformed, anisotropic solids is reviewed with emphasis on those features which might be used to distinguish between stress induced changes in ultrasonic velocity and changes due to material anisotropy, such as would be produced by preferred grain orientation in a polycrystalline metal As noted by previous authors, one such feature is the difference in velocity of two shear waves, whose directions of propagation and polarization have been interchanged. In particular, when these directions fall along the symmetry axes of a rolled plate (assuming orthorhombic symmetry) and these are also the directions of ...

Evaluation Of Residual Stress States Using Horizontally Polarized Shear Waves, R. B. King, C. M. Fortunko

#### Evaluation Of Residual Stress States Using Horizontally Polarized Shear Waves, R. B. King, C. M. Fortunko

*Review of Progress in Quantitative Nondestructive Evaluation*

A new approach for using acoustic measurements to evaluate residual stresses in the presence of unknown material property variations is presented. It is shown that measurements using shear waves propagating along the normal to the surface of a plate do not provide sufficient information to separate the influences of stress and material property variations. To overcome this fundamental limitation, an alternative theory is developed that governs the propagation of shear waves polarized horizontally with respect to the surface of a plate (SH-waves), but propagating at oblique angles with respect to the surface normal. The question of separating the effects of ...

Detection Of Strain Induced Microstructural Changes In Aluminum (6061-T6) Using Ultrasonic Signal Analysis, G. H. Thomas, S. H. Goods, A. F. Emery

#### Detection Of Strain Induced Microstructural Changes In Aluminum (6061-T6) Using Ultrasonic Signal Analysis, G. H. Thomas, S. H. Goods, A. F. Emery

*Review of Progress in Quantitative Nondestructive Evaluation*

A correlation between the change in ultrasonic wave forms and applied strain in aluminum (6061-T6) has been obtained at high strain levels. Sophisticated signal processing techniques have indicated a complex interaction of the frequency components of a high frequency ultrasonic pulse as it passes through an aluminum tensile specimen. Strain induced microstructural changes in the aluminum attenuate the acoustic energy. One of the attenuation mechanisms is the formation of deformation induced cavities at precipitates and inclusions which scatter the ultrasonic energy. Measuring the signal attenuation at the appropriate frequencies determines the degree of deformation induced damage.

The Use Of Acoustic Signal Attenuation In The Examination Of Residual Strains: Part B — The Use Of Experimentally Derived Acoustic Strain Correlations In The Evaluation Of Residual Strains And Stresses, A. F. Emery, G. H. Thomas

#### The Use Of Acoustic Signal Attenuation In The Examination Of Residual Strains: Part B — The Use Of Experimentally Derived Acoustic Strain Correlations In The Evaluation Of Residual Strains And Stresses, A. F. Emery, G. H. Thomas

*Review of Progress in Quantitative Nondestructive Evaluation*

In a previous conference we presented a comparison of several different acoustic techniques to estimate residual stresses in complex situations.1 Of the several methods, the use of the attenuation of broad band pulses appeared to be better than the usual method of inferring strain from changes in the propagation velocity. The measurement of strain through changes in the velocity is effected through the equations 1 ΔV/V = f(εij), 2 Δt/t=Δd/d−ΔV/V where εij = strain tensor, t = time for the wave to traverse the specimen, d = specimen thickness, V = wave velocity.

The Use Of The Temperature Dependence Of Ultrasonic Velocity To Measure Residual Stress, K. Salama, J. J. Wang, G. C. Barber

#### The Use Of The Temperature Dependence Of Ultrasonic Velocity To Measure Residual Stress, K. Salama, J. J. Wang, G. C. Barber

*Review of Progress in Quantitative Nondestructive Evaluation*

The behavior of the temperature dependence of longitudinal ultrasonic velocity in type A533B steel in the presence of external as well as residual stresses has been investigated. In all measurements, the ultrasonic velocity in the vicinity of room temperature is found to vary linearly with temperature, and the slope of the linear relationship increases or decreases according to whether the stress is applied in tension or in compression respectively. The results also indicate that the temperature dependence of the velocity is a linear function of applied stress, and the slope of this linear relationship is the same for all specimens ...

Ultrasonic Determination Of Grain Size In Uranium, William D. Brosey

#### Ultrasonic Determination Of Grain Size In Uranium, William D. Brosey

*Review of Progress in Quantitative Nondestructive Evaluation*

An ultrasonic technique has been developed that enables measurement of grain size in uranium without metallographic preparation or destructive analysis. Pitch-catch ultrasonic analysis using transverse (shear) waves was conducted in the determination of grain size in wrought uranium parts.

Ultrasonic Steel Cleanliness System, James M. Smith

#### Ultrasonic Steel Cleanliness System, James M. Smith

*Review of Progress in Quantitative Nondestructive Evaluation*

It is well known that nonmetallic inclusions can adversely affect the metallurgical properties of engineering alloys. For critical components such as aircraft engine gears and bearings it is important then to quantitatively assess the severity of the inclusion content in the alloy material before performing costly manufacturing operations. This poster paper will describe the operation and the initial results of a computer controlled steel cleanliness inspection system.

The severity of the inclusion content is determined by this system through a statistical analysis of the internally reflected ultrasonic indications from the alloy material as a transducer is scanned in a raster ...

A Portable High Speed Ultrasonic Imaging System, B. P. Hildebrand, T. J. Davis, A. J. Boland, R. R. Silta

#### A Portable High Speed Ultrasonic Imaging System, B. P. Hildebrand, T. J. Davis, A. J. Boland, R. R. Silta

*Review of Progress in Quantitative Nondestructive Evaluation*

Acoustical holography is rapidly approaching commercial status with applications to nondestructive evaluation, underwater imaging, and underground pipe location being pursued. In this paper we review the techniques involved, show some experimental results, and describe the latest commercial system.

Application Of Fourier Elastodynamics To Direct And Inverse Problems For The Scattering Of Elastic Waves From Flaws Near Surfaces, J. M. Richardson, K. W. Fertig Jr.

#### Application Of Fourier Elastodynamics To Direct And Inverse Problems For The Scattering Of Elastic Waves From Flaws Near Surfaces, J. M. Richardson, K. W. Fertig Jr.

*Review of Progress in Quantitative Nondestructive Evaluation*

In ultrasonic inspection one frequently encounters situations in which flaws lie too close to surfaces (or interfaces) for the applications of the conventional theory of scattering in an infinite host medium. One approach, pursued by Varadan, Pillai, and Varadan, is to rework scattering theory with a Green function suitably modified for the presence of surfaces. Our approach uses a Fourier elastodynamics formalism in which the scattering process is represented by the generalized transfer function for a slab of material containing the flaw. A sufficiently simple elastodynamic system can be built up of separately characterizable subsystems defined by intervals on the ...

Wave Scattering By Obstacles In Joined Fluid-Solid Half Spaces, V. V. Varadan, T. A. K. Pillai, V. K. Varadan

#### Wave Scattering By Obstacles In Joined Fluid-Solid Half Spaces, V. V. Varadan, T. A. K. Pillai, V. K. Varadan

*Review of Progress in Quantitative Nondestructive Evaluation*

In recent years, attention has shifted from the ultrasonic NDE of bulk flaws to flaws in structural components that involve nearby surfaces. Very often it is convenient to exajnine the part in a water tank, locating the transmitting/receiving transducers in water. This paper is concerned with a theoretical study of a near surface flaw in an immersion tank experiment. The analytical problem to be studied is the scattering of ultrasound by an obstacle that is located near a solid-fluid (water) interface. The distance ‘d’ of the center of the flaw from the interface ranges from ‘a’ to ‘15a’ where ...

Scattering By Flaws In A Slab Or A Half-Space, William M. Visscher

#### Scattering By Flaws In A Slab Or A Half-Space, William M. Visscher

*Review of Progress in Quantitative Nondestructive Evaluation*

It is the main function of quantitative NDE to detect and to evaluate defects. Some of the most dangerous defects are cracks, especially cracks on or near surfaces. These cracks can be found by scattering ultrasonic waves from them (either bulk waves or surface waves), but up to now there is no theory (at least in the most interesting low-to-intermediate frequency region) which has been implemented to compute scattering from surface or near-surface cracks in 3d. The purpose of the present report is to explain, via a simple scalar example, the principles of a general boundary-integral-representation method which has been ...

Effects Of Microstructure On The Speed And Attenuation Of Elastic Waves: Formal Theory And Simple Approximations, J. E. Gubernatis, E. Domany

#### Effects Of Microstructure On The Speed And Attenuation Of Elastic Waves: Formal Theory And Simple Approximations, J. E. Gubernatis, E. Domany

*Review of Progress in Quantitative Nondestructive Evaluation*

The sensitivity of the propagation of an elastic wave to changes in the microstructural details of a material is well known.1 In particular, numerous experiments have shown that the attenuation of the wave is sensitive to the inclusions, voids, cracks, grain boundaries, twin boundaries, interphase boundaries, magnetic domain walls, dislocations, substitutional impurities of a material. For attenuation studies in metals, ceramics and polycrystals, three formulas, each for different wavelength regimes, are generally used in the quantitative interpretation of experimental results.1–3 If λ is the wavelength of the elastic wave and is the average grain diameter, then in ...

On The Estimation Of Porosity In Composites By Oblique Angle Illumination, A. C. Kak, Mani Azimi, Malcolm Slaney

#### On The Estimation Of Porosity In Composites By Oblique Angle Illumination, A. C. Kak, Mani Azimi, Malcolm Slaney

*Review of Progress in Quantitative Nondestructive Evaluation*

Reported here are some preliminary computer simulation results on the feasibility of using oblique incidence ultrasound for the detection and estimation of porosity in composites. In the oblique incidence approach, the composite is illuminated at off normal angles in such a manner that the reflected returns from the fibers are in directions away from the illuminating transducer. Since the scattered returns from porosity tend to be more omnidirectional than the fiber returns, there is a larger received signal in the presence of porosity.

Elastic Wave Scattering From Multiple Voids (Porosity), Donald O. Thompson, Samuel J. Wormley, James H. Rose, R. Bruce Thompson

#### Elastic Wave Scattering From Multiple Voids (Porosity), Donald O. Thompson, Samuel J. Wormley, James H. Rose, R. Bruce Thompson

*Review of Progress in Quantitative Nondestructive Evaluation*

The purpose of the work described in this paper is the development of an ultrasonic measurement technique which provides a convenient way to detect dilute porosity conditions in materials and to extract certain properties of the flaw distribution which are important in failure prediction. Use has been made entirely of ultrasonic backscatter measurements; thus, the technique differs considerably from other investigations which lead to porosity determinations in that no reliance is placed upon either attenuation measurements or precise ultrasonic velocity measurements [1,2]. The technique thus possesses a distinct advantage for practical implementation, i.e., it is a “one-sided” measurement ...

Backscattering Of Ultrasonic Leaky Waves From Liquid-Solid Interfaces, Laszlo Adler, Ken Bolland, Michel De Billy, Gerard Quentin

#### Backscattering Of Ultrasonic Leaky Waves From Liquid-Solid Interfaces, Laszlo Adler, Ken Bolland, Michel De Billy, Gerard Quentin

*Review of Progress in Quantitative Nondestructive Evaluation*

It is well known that when a finite ultrasonic beam of a given spatial distribution is incident at the Rayleigh angle to a liquid-solid interface, the spatial distribution of the reflected field may be altered significantly. The “energy redistribution” is due to the interference between the specularly reflected beam and a surface wave which has leaked back to the water. The “shape” of the reflected field depends on the so-called Schoch displacement (which is characteristic of the interface) and on the width of the ultrasonic beam. It has also been observed that significant energy is scattered back to the transmitter ...

An Inverse Problem In Viscoelasticity, Lewis Thigpen, Gerald W. Hedstrom, Brian P. Bonner

#### An Inverse Problem In Viscoelasticity, Lewis Thigpen, Gerald W. Hedstrom, Brian P. Bonner

*Review of Progress in Quantitative Nondestructive Evaluation*

Calculation of attenuation and dispersion spectra for a general anelastic body may be posed as an inversion problem. We observe the time-dependent strain due to “instantaneous” changes in stress in order to characterize the anelastic response. This experimental technique reaches a range of frequencies which is lower than that used in resonance bar experiments, but we can make only indirect measurement of the viscoelastic properties. We employ the most general anelastic model which states that the observed compliance is due to the summed effect of an arbitrary spectrum of mechanisms. The analysis requires the solution of Fredholm integral equations of ...

Inverse Ray Tracing In Anisotropic Elastic Solids, Andrew Norris

#### Inverse Ray Tracing In Anisotropic Elastic Solids, Andrew Norris

*Review of Progress in Quantitative Nondestructive Evaluation*

The problem of inverse ray tracing in a homogeneous anisotropic elastic solid is considered, with specific application to crack sizing. The data is assumed to be in the form of travel times of diffracted ultrasonic signals between transducers positioned on an exterior surface of the body. Both pulse-echo and pitch-catch data are considered. First, it is assumed that the wave speeds are unknown and must be obtained as part of the inversion procedure. The specific problem of locating a crack tip in a two-dimensional geometry is investigated. It is found that travel time data on the exterior surface suffices to ...

On Nonspecular Reflection Of Bounded Beams For Layered Half Spaces Under Water, D. B. Bogy, S. M. Gracewski

#### On Nonspecular Reflection Of Bounded Beams For Layered Half Spaces Under Water, D. B. Bogy, S. M. Gracewski

*Review of Progress in Quantitative Nondestructive Evaluation*

We study the recently derived reflection coefficient for plane waves in a liquid that are incident on the liquid-solid interface of a solid half space which consists of a single layer of one elastic material bonded to a substrate of a different material. Plots of the magnitude of the reflection coefficient versus the incident angle are presented for several sets of material parameters and values of frequency f and layer thickness d. The use of the results presented for the study of nonspecular reflection of bounded acoustic beams is of primary interest. We therefore seek to identify all the critical ...

The Maximum Entropy Formulation Of Inverse Problems Of Nde, R. M. Bevensee

#### The Maximum Entropy Formulation Of Inverse Problems Of Nde, R. M. Bevensee

*Review of Progress in Quantitative Nondestructive Evaluation*

This paper introduces the Maximum Entropy method of resolving underdetermined objects (flaws or inclusions) by a physicists’ brand of nonlinear processing of the image data. We survey three areas of research: (1) synthetic aperture imaging to resolve three dimensional flaws, with the aid of selective back projection, (2) scattering from anomalies according to the inhomogeneous Fredholm integral equation of the second kind, and (3) ultrasonic flaw characterization by the boundary integral equation method. A simple example is offered to illustrate the potential resolving power of the ME method for problems in area (2). We present some criteria for effective ME ...

Cure Monitoring Of Thermosetting Polymers By An Ultrasonic Technique, Donald L. Hunston

#### Cure Monitoring Of Thermosetting Polymers By An Ultrasonic Technique, Donald L. Hunston

*Review of Progress in Quantitative Nondestructive Evaluation*

In the fabrication of components with thermosetting polymers, an essential step is the proper optimization of the cure cycle. In the early phases of the cure the polymer must have the appropriate flow properties to assure the proper wetting, spreading, and forming. It must then harden without excessive build up of residual stresses and flaws or the loss of adhesion at any interfaces that are present. To complicate the situation further, many applications such as composites, adhesives, paints, and protective coatings involve thin films whose cure behavior is significantly different than that for bulk samples. To help address this problem ...

Ultrasonic Signal Processing For Multilayered Nde, Ramesh Shankar, Stephen S. Lane, Jeffrey M. Warren

#### Ultrasonic Signal Processing For Multilayered Nde, Ramesh Shankar, Stephen S. Lane, Jeffrey M. Warren

*Review of Progress in Quantitative Nondestructive Evaluation*

The interpretation of ultrasonic signals in the inspection for flaws in bonded regions of multilayered specimens is difficult because of signal energy loss due to material attenuation, undesired reverberations within certain layers, and overlapping responses from different interfaces because of finite transducer bandwidth. The flaws are usually air gaps, lack of adhesion, and porosity within the bonding agent.

While ultrasonic NDE signal interpretation can always be improved with appropriate instrumentation — broader bandwidth transducers for increased resolution, for example — signal processing allows for further enhancement using a digital computer. Material attenuation can be compensated for by using digital filters that preferentially ...