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Full-Text Articles in Engineering Science and Materials

The Radiation Of Elliptical And Bicylindrically Focused Piston Transducers, R. Bruce Thompson, T. A. Gray, J. H. Rose, V. G. Kogan, E. F. Lopes Nov 1987

The Radiation Of Elliptical And Bicylindrically Focused Piston Transducers, R. Bruce Thompson, T. A. Gray, J. H. Rose, V. G. Kogan, E. F. Lopes

Ames Laboratory Publications

Expressions for the radiation of elliptical and bicylindrically focused piston transducers are derived within the Fresnel approximation. For the axial fields, the result takes the form of either a simple analytical expression (small perturbations from the circular piston case), a single quadrature in a real variable (unfocused and some focused cases), or a single quadrature in a complex variable (near focal points). The full fields are represented by a series of localized, Gauss–Hermite eigenfunctions. Numerical examples are used to illustrate the agreement of the two solutions for on‐axis fields and to shed light on questions of the convergence ...


A Study On The Effect Of Dislocation On The Magnetic Properties Of Nickel Using Magnetic Nde Methods, R. Ranjan, O. Buck, R. Bruce Thompson Apr 1987

A Study On The Effect Of Dislocation On The Magnetic Properties Of Nickel Using Magnetic Nde Methods, R. Ranjan, O. Buck, R. Bruce Thompson

Ames Laboratory Publications

Dislocations affect the magnetic properties of ferromagnetic materials by pinning the domain walls. The primary mechanism is interaction between the stress fields of dislocation and domain walls. Using magnetic nondestructive methods, namely the acoustic Barkhausen noise (AB), magnetic Barkhausen noise (MB), and the hysteresis curves, we have studied these interactions. The three measurements give different types of information. AB provides information about non‐180° type domain wall interaction, MB primarily provides information about 180° domain wall interaction, and the hysteresis curve about both these interactions as well as about rotation of domain walls. The paper presents results obtained on polycrystalline ...


Grain Size Measurement Using Magnetic And Acoustic Barkhausen Noise, R. Ranjan, David C. Jiles, Otto Buck, R. Bruce Thompson Apr 1987

Grain Size Measurement Using Magnetic And Acoustic Barkhausen Noise, R. Ranjan, David C. Jiles, Otto Buck, R. Bruce Thompson

Ames Laboratory Publications

Results on annealed nickel show that the total number of counts of both magnetic and acoustic Barkhausen signals vary inversely with grain size. In decarburized steels the total number of counts and the amplitude of both Barkhausen signals increase in proportion to grain size. The paper addresses these results in context of grain size, grain‐boundary segregation, and precipitate effect.


Compressive Stress Effects On The Ultrasonic Detection Of Cracks In Welds, Thomas A. Siewert, Raymond E. Schramm Jan 1987

Compressive Stress Effects On The Ultrasonic Detection Of Cracks In Welds, Thomas A. Siewert, Raymond E. Schramm

Review of Progress in Quantitative Nondestructive Evaluation

Crack closure due to external bending forces or residual stresses is an important concern in any nondestructive examination. It is particularly important in ultrasonic examination since this technique depends on the change in acoustic impedance at the crack interface to produce the reflected wave. If the two surfaces come into intimate contact somewhere along the crack due to closure effects, partial transmission can occur [1]. This partial transmission reduces the reflected signal and so underestimates the flaw depth when sizing is based on the reflected signal amplitude.


Determining Crack Tip Shielding By Means Of Acoustic Transmission And Diffraction Measurements, Otto Buck, David K. Rehbein, R. Bruce Thompson Jan 1987

Determining Crack Tip Shielding By Means Of Acoustic Transmission And Diffraction Measurements, Otto Buck, David K. Rehbein, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

Asperity contact along the fracture surface of a crack is one of the mechanisms of crack closure. This contact shields the crack tip, in part, from the externally applied driving force on the crack. We have now succeeded in using experimental information, obtained under plane strain conditions from acoustic transmission and diffraction experiments in the closure region [1,2] to determine a stress intensity factor, KI(local), which shields the crack tip below a stress intensity factor KIclosure a t first contact during unloading occurs.


Ultrasonic Attenuation As A Trace Of Growth Of Fatigue Crack In Steels, Zhengliang Pan Jan 1987

Ultrasonic Attenuation As A Trace Of Growth Of Fatigue Crack In Steels, Zhengliang Pan

Review of Progress in Quantitative Nondestructive Evaluation

Two comprehensive overviews on ultrasonic quantitative nondestructive evaluation and materials characterization were recently given by Thompson [1] and Green [2] respectively. Ultrasonic attenuation measurements are used to study a great variety of material microstructures and associated mechanical properties. On the other hand, fracture mechanics provides a basis for some failure models for cracks, inclusions, voids, etc. A fracture mechanical analysis for ultrasonic measurements in cracked specimens should give some new informations, which will be useful for quantitative NDE.


Evaluation Of Strain-Induced Surface Changes By Optical Correlation, Nam Soon Chang, W. L. Haworth Jan 1987

Evaluation Of Strain-Induced Surface Changes By Optical Correlation, Nam Soon Chang, W. L. Haworth

Review of Progress in Quantitative Nondestructive Evaluation

Previous experiments in our laboratory [1,2] have demonstrated that changes in optical correlation intensity can be used to monitor small strain applied, for example, to aluminum alloy specimens in simple tension. By analyzing data separately for specimen translation, elastic strain, and plastic strain, respectively, we inferred that irreversible changes in correlation intensity associated with plastic strains of the order of 10-3 are caused by accompanying changes in surface topography [2]. In this paper, we present results which link metallographic observations of surface slip and related topographic changes directly to corresponding changes in optical correlation intensity, during uniaxial tensile straining ...


Nde Positron Study Of Cu And Cu-Al Alloys Thermally Charged With Hydrogen And Deformed, Yi Pan, J. G. Byrne Jan 1987

Nde Positron Study Of Cu And Cu-Al Alloys Thermally Charged With Hydrogen And Deformed, Yi Pan, J. G. Byrne

Review of Progress in Quantitative Nondestructive Evaluation

Some aspects of the deformation of Cu, Cu-2 w/o Al, and Cu-4 w/o Al alloy samples after thermal charging with hydrogen at 1000ºC and rapid quenching (to -150ºC isopentane) were treated in an earlier publication [1]. Comparisons were made with samples treated as just described except for use of an Ar atmosphere at 1000°C. The main experimental measurements then as now were of the Doppler broadening of the positron annihilation spectrum and the microhardness. The deformation was imposed by a Brinell indentation of 500 kgf.


Nondestructive Characterization Of Aluminum Alloys, S. Razvi, P. Li, K. Salama, J. H. Cantrell Jr., W. T. Yost Jan 1987

Nondestructive Characterization Of Aluminum Alloys, S. Razvi, P. Li, K. Salama, J. H. Cantrell Jr., W. T. Yost

Review of Progress in Quantitative Nondestructive Evaluation

In order to determine the integrity and safety of a structure, any fracture mechanics model requires information about the size, location and geometry of a defect, the mechanical properties of the material, and the stress field in the vicinity of the defect. The stress can be due to external forces or due to residual stresses. Current nondestructive evaluation techniques can determine the size, location and to some extent the geometry of defects. However, there are no simple methods by which mechanical properties of a material can be characterized nondestructively or the stresses in a component can be measured or analysed.


Characterization Of Impact Damage In Composites, C. F. Buynak, T. J. Moran Jan 1987

Characterization Of Impact Damage In Composites, C. F. Buynak, T. J. Moran

Review of Progress in Quantitative Nondestructive Evaluation

This paper will report on the results of a study of the application of advanced digital data acquisition technology to the problem of impact damage in composites. This area was chosen for the study because of the importance of developing better damage characterization methods and the limited scope of the damage itself. Low energy impacts on composite specimens typically produce very small indentations at the impact site and internal delaminations at the interfaces between lamina. Thus, one can very accurately set the ultrasonic time gates for imaging the delaminations on a layer-by-layer basis.


Analytical Treatment Of Polar Backscattering From Porous Composites, J. Qu, Jan D. Achenbach Jan 1987

Analytical Treatment Of Polar Backscattering From Porous Composites, J. Qu, Jan D. Achenbach

Review of Progress in Quantitative Nondestructive Evaluation

Polar backscattering from a fiber-reinforced composite which contains regions of porosity, consists of several components. Roughly speaking these components can be attributed to effects of finite beam width, to the structuring of the material and to the existence of porosity. The backscatter amplitude strongly depends on the polar and the azimuthal angles, which together define the position of the transducer. It has been shown experimentally that the backscatter amplitude shows a steep peak when the incident beam is normal to the fiber direction [l]–[4].


Porosity Characterization In Fiber-Reinforced Composites By Use Of Ultrasonic Backscatter, Ronald A. Roberts Jan 1987

Porosity Characterization In Fiber-Reinforced Composites By Use Of Ultrasonic Backscatter, Ronald A. Roberts

Review of Progress in Quantitative Nondestructive Evaluation

The use of ultrasonic backscatter to characterize anomalous states in fiber-reinforced composites has received considerable attention in recent years. The ultrasonic backscatter from composites with oriented fiber reinforcement, unlike that from monolithic materials, displays a strong angular dependence. Hence, three independent variables are available over which to analyze the backscatter. These are the azimuthal angle ∅ (the rotation orientation of the composite plate about the perpendicular), the elevation angle θ (the angle between the ultrasonic beam and the perpendicular to the insonified composite plate), and time. Bar-Cohen and Crane [1] considered various ways of exploiting the angular dependence of backscatter to ...


Acoustic Wave Reflection From Water/Laminated Composite Interfaces, Adrian H. Nayfeh Jan 1987

Acoustic Wave Reflection From Water/Laminated Composite Interfaces, Adrian H. Nayfeh

Review of Progress in Quantitative Nondestructive Evaluation

The high specific strength and stiffness of composite materials has led to their widespread use in efficient structures. Since most of these structures are subjected to cyclic loads which can lead to rapid degradation in load carrying capability, initial inspection and continued monitoring of these materials for detection and sizing of strength degrading flaws is necessary in order to ensure adequate structural reliability. Unfortunately, many of the current inspection techniques can not be directly utilized for this purpose because of the inhomogeneous, anisotropic nature of composites. In addition, the types and numbers of internal flaws that must be detected and ...


Estimating Residual Strength In Filament Wound Casings From Nondestructive Evaluation Of Impact Damage, Eric I. Madaras, Clarence C. Poe Jr., Walter Illg, Joseph Heyman Jan 1987

Estimating Residual Strength In Filament Wound Casings From Nondestructive Evaluation Of Impact Damage, Eric I. Madaras, Clarence C. Poe Jr., Walter Illg, Joseph Heyman

Review of Progress in Quantitative Nondestructive Evaluation

The purpose of this study is to improve the ability to detect hidden impact damage in thick composites caused by low velocity impact and to predict the remaining strength of those materials. An impact study has been undertaken on filament wound graphite/epoxy casings, such as those proposed for NASA’s space shuttle solid fuel rocket boosters. In thick composite materials, low-velocity impact damage may not be visually evident, depending on the impacter shape; yet the damage may compromise the composite’s ultimate strength. A model of a filament wound casing was fabricated with one fifth of the diameter (30 ...


Resolution Of Closely-Spaced Machining-Damage-Induced Surface Cracks In Ceramics, L. R. Clarke, B. T. Khuri-Yakub, D. B. Marshall Jan 1987

Resolution Of Closely-Spaced Machining-Damage-Induced Surface Cracks In Ceramics, L. R. Clarke, B. T. Khuri-Yakub, D. B. Marshall

Review of Progress in Quantitative Nondestructive Evaluation

Machining damage to structural ceramics is complex; a single machining crack consists of a series of continuous and overlapping semielliptical surface flaws between about 10 and 100 μm deep, as shown schematically in Fig, 1a. The mouths of these flaws are held closed by a layer of compressive residual stresses induced by the irreversible plastic deformations and material removal occuring during machining. Beneath the compressive layer is a zone of weak tension which separates the subsurface portions of the flaw faces. These residual stress fields permit stable crack growth to about 4.5 times the initial flaw depth prior to ...


A Linearization Beam-Hardening Correction Method For X-Ray Computed Tomographic Imaging Of Structural Ceramics, E. Segal, W. A. Ellingson, Y. Segal, I. Zmora Jan 1987

A Linearization Beam-Hardening Correction Method For X-Ray Computed Tomographic Imaging Of Structural Ceramics, E. Segal, W. A. Ellingson, Y. Segal, I. Zmora

Review of Progress in Quantitative Nondestructive Evaluation

Computed tomographic (CT) imaging with both monochromatic and polychromatic x-ray sources can be a powerful NDE method for characterization (e. g., measurement of density gradients) as well as flaw detection (e. g., detection of cracks, voids, inclusions) in ceramics. However, the use of polychromatic x-ray sources can cause image artifacts and overall image degradation through beam hardening (BH) effects [1]. Beam hardening occurs because (i) x-ray attenuation in a given material is energy dependent and (ii) data collection in CT systems is not energy selective. Without an appropriate correction, the BH effect prevents the establishment of an absolute scale for ...


Applications Of Film Tomography Technique For Qnde, A. Notea Jan 1987

Applications Of Film Tomography Technique For Qnde, A. Notea

Review of Progress in Quantitative Nondestructive Evaluation

Tomography with X- and gamma- rays provides three-dimensional radiographic information on the examined object. The film-based tomography (1,2) generates a summation-image of a surface within the object by continuously combining back projections directly on the film. This method has many attractive features for industrial applications in which cost and simplicity are of primary importance. Some of the features are: (1) The absence of post processing allows this method to yield an image immediately on development of the film.; (2) Conventional radiologists need a short training time to master the technique as most components and concepts are familiar to them ...


Photon Ct Scanning Of Advanced Ceramic Materials, B. D. Sawicka, W. A. Ellingson Jan 1987

Photon Ct Scanning Of Advanced Ceramic Materials, B. D. Sawicka, W. A. Ellingson

Review of Progress in Quantitative Nondestructive Evaluation

Advanced ceramic materials (e. g. Si3N4, ZrO2, SiC, A12O3) are being developed for high temperature applications in advanced heat engines and high temperature heat recovery systems [1]. Although fracture toughness has been a constant problem, advanced ceramics are now being developed with fracture toughnesses close to those of metals [2]. Small size flaws (10–200 μm), small non-uniformities in density distributions (0.1–2%) present as long-range density gradients, and porous regions which can be seen as localized areas of slightly lower density, are critical in most ceramics. The need to detect these small flaws is causing a significant effort ...


Simultaneous Measurements Of Ultrasonic Phase Velocity And Attenuation In Solids, N. K. Batra, P. P. Delsanto Jan 1987

Simultaneous Measurements Of Ultrasonic Phase Velocity And Attenuation In Solids, N. K. Batra, P. P. Delsanto

Review of Progress in Quantitative Nondestructive Evaluation

Several techniques have been proposed for the ultrasonic characterization of metals, ceramics and composite materials. For highly attenuative materials, e. g., fiber-reinforced composites, either the sound phase velocity, or the attenuation can usually be determined. In this paper, we extend the correlation method for simultaneous measurement of phase velocity and attenuation in liquids, first proposed by Sedlacek and Asenbaum1, to the case of highly attenuative solids. By using specially designed specimens in the shape of wedges, the path of propagation can be continuously varied. Cross-correlations of pressure amplitude and phase between different points in the field of continuous ultrasonic plane ...


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].


Internal Monitoring Of Acoustic Emission In Graphite-Epoxy Composites Using Imbedded Optical Fiber Sensors, K. D. Bennett, R. O. Claus, M. J. Pindera Jan 1987

Internal Monitoring Of Acoustic Emission In Graphite-Epoxy Composites Using Imbedded Optical Fiber Sensors, K. D. Bennett, R. O. Claus, M. J. Pindera

Review of Progress in Quantitative Nondestructive Evaluation

The monitoring of acoustic emission (AE) is an important technique for the nondestructive characterization of strained materials because time and frequency domain analyses of AE events yield information about the type, geometry, and location of defects, as well as how material failure may occur. The quantitative interpretation of AE event signatures is critically dependent upon the faithfulness of the acoustic transduction and signal processing system in reproducing localized stress wave amplitude as a function of time. Although the usual sensor for acoustic emission is the piezoelectric transducer, several investigators have considered the application of interferometric optical sensing techniques which offer ...


Engineering Tomography: A Quantitative Nde Tool, Richard L. Hack, Donna K. Archipley-Smith, William H. Pfeifer Jan 1987

Engineering Tomography: A Quantitative Nde Tool, Richard L. Hack, Donna K. Archipley-Smith, William H. Pfeifer

Review of Progress in Quantitative Nondestructive Evaluation

The development and application of advanced materials, whether composite, metal matrix or ceramic, has progressed to a point where qualitative non-destructive inspection of components is no longer sufficient. As confidence in the validity of material properties increases, structures utilizing these advanced materials will be designed without the excessive safety factors characteristic of earlier structures utilizing the same materials. While this trend has the advantage of economizing on the use of the advanced, expensive materials, it underscores the need to quantify the flaw structure of advanced material components so that accurate, flawed material thermostructural response can be predicted and so that ...


Ultrasonic Nondestructive Evaluation Of Fibre-Reinforced Composite Materials - A Review, Vikram K. Kinra, Vinay Dayal Jan 1987

Ultrasonic Nondestructive Evaluation Of Fibre-Reinforced Composite Materials - A Review, Vikram K. Kinra, Vinay Dayal

Vinay Dayal

This paper reviews various ultrasonic nondestructive evaluation techniques applicable to fibre-reinforced composites. The techniques are briefly described and key references are cited. Methods to evaluate the reduced stiffness of composites due to micro-damage are described. Results show that for composites through-the-thickness attenuation increases and stiffness does not change due to transverse cracks, but in-plane stiffness and attenuation changes are substantial and can be measured by the Lamb wave techniques.