Influence of Columnar Microstructure on Ultrasonic Backscattering

Ahmed, S.; Thompson, R. B.

doi:10.1007/978-1-4615-1987-4_207

Cited by 21 publications

(13 citation statements)

References 9 publications

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“…5,6 They further noted the relations between the diffuse backscatter and the presence of texture. 7 The general scattering problem as discussed by these authors and others involves a scattering integral with a Green's function as its kernel. If the medium is statistically isotropic, this Green's function clearly takes the form of the Green's function for the isotropic medium.…”

Section: Introductionmentioning

confidence: 99%

Elastic wave propagation and scattering in heterogeneous, anisotropic media: Textured polycrystalline materials

Turner

1999

The Journal of the Acoustical Society of America

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The propagation of elastic waves through heterogeneous, anisotropic media is considered. Appropriate ensemble averaging of the elastic wave equation leads to the Dyson equation which governs the mean response of the field. The Dyson equation is given here in terms of anisotropic elastic Green's dyadics for the medium with and without heterogeneities. The solution of the Dyson equation for the mean response is given for heterogeneities that are weak. The formalism is further specified for the case of equiaxed cubic polycrystalline metals with a single aligned axis. The Green's dyadics in this case are those for a transversely isotropic medium. Simple expressions for the attenuations of the shear horizontal, quasicompressional, and quasishear waves are given in terms of integrations on the unit circle. The derived expressions are limited to frequencies below the geometric optics limit, but give the attenuations in a direct manner. Comparisons with previous results are also discussed. It is anticipated that a similar approach is necessary for the study of wave propagation in complex anisotropic materials such as fiber-reinforced composites. In addition, the results are applicable to diffuse ultrasonic inspection of textured polycrystalline media.

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Section: Introductionmentioning

confidence: 99%

Elastic wave propagation and scattering in heterogeneous, anisotropic media: Textured polycrystalline materials

Turner

1999

The Journal of the Acoustical Society of America

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“…Grain sizing was performed following ISO 13067 using OIM data analysis software. Figure 9 depicts the grain maps used for data analysis; the colors correspond with unique grains defined by crystallographic misorientation greater than 10 . Note that these maps are not representative of texture in the material as the individual colors do not correspond with a particular grain orientation; white spaces in the maps correspond with areas with an insufficient number of points properly indexed (more than 100 indexed points were required for a given area to be considered a grain).…”

Section: Resultsmentioning

confidence: 99%

“…Ahmed and Thompson 10 followed an approach similar to Rose [6][7][8] and Margetan 9 to define longitudinal scattering from polycrystals with ellipsoidal grains of circular cross-section; the effect of elongation was included by modifying the spatial correlation function which defines the spatial dependence of the grain statistics. Later, Han and Thompson 11 followed a similar formalism to study the case of polycrystals with duplex microstructures.…”

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confidence: 99%

Mode-converted ultrasonic scattering in polycrystals with elongated grains

Argüelles

Kube

et al. 2016

The Journal of the Acoustical Society of America

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Elastic wave scattering is used to study polycrystalline media for a wide range of applications. Received signals, which include scattering from the randomly oriented grains comprising the polycrystal, contain information from which useful microstructural parameters may often be inferred. Recently, a mode-converted diffuse ultrasonic scattering model was developed for evaluating the scattered response of a transverse wave from an incident longitudinal wave in a polycrystalline medium containing equiaxed single-phase grains with cubic elastic symmetry. In this article, that theoretical mode-converted scattering model is modified to account for grain elongation within the sample. The model shows the dependence on scattering angle relative to the grain axis orientation. Experimental measurements were performed on a sample of 7475-T7351 aluminum using a pitchcatch transducer configuration. The results show that the mode-converted scattering can be used to determine the dimensions of the elongated grains. The average grain shape determined from the experimental measurements is compared with dimensions extracted from electron backscatter diffraction, an electron imaging technique. The results suggest that mode-converted diffuse ultrasonic scattering has the potential to quantify detailed information about grain microstructure.

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“…Elastic Constants of IN718 were deduced by fitting to measured attenuation and backscattered data using specimens with known grain size. certain FOM formulas for non-equiaxed microstructures that had been derived earlier by Bruce and a post-doctoral student Salahuddin Ahmed [25]. Using the UT setups depicted in Fig.…”

Section: Exploiting the Relationship Between Fom And Microstructurementioning

confidence: 98%

“…1. Postdoctoral associate Salahuddin Ahmed worked with Bruce to explore the effects of grain elongation and preferred grain orientation on ultrasonic attenuation and backscatter in metals [49,50]. His research set the stage for Yanming Guo's grain sizing work discussed earlier in connection with Fig.…”

Section: Closing Commentsmentioning

confidence: 99%

Bruce Thompson: Adventures and advances in ultrasonic backscatter

Margetan¹

2012

AIP Conference Proceedings

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Influence of Columnar Microstructure on Ultrasonic Backscattering

Cited by 21 publications

References 9 publications

Elastic wave propagation and scattering in heterogeneous, anisotropic media: Textured polycrystalline materials

Elastic wave propagation and scattering in heterogeneous, anisotropic media: Textured polycrystalline materials

Mode-converted ultrasonic scattering in polycrystals with elongated grains

Bruce Thompson: Adventures and advances in ultrasonic backscatter

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