Looking for Multiple Scattering Effects in Backscattered Ultrasonic Grain Noise from Jet-Engine Nickel Alloys

Margetan, F. J.; Haldipur, P.; Yu, Liangli; Thompson, R. B.

doi:10.1063/1.1916662

Cited by 19 publications

(9 citation statements)

References 6 publications

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“…Other scattering configurations where the incident wave is scattered into an arbitrary direction are dependent on other components of N abcd ijkl . [48][49][50] Additionally, other scattering related phenomenon such as ultrasonic attenuation [21][22][23][24][25]51 and radiative transfer of ultrasound 48,[52][53][54] depend on inner products with N. The stress-dependence of each of these models is included by using the definition of N defined in this article.…”

Section: Resultsmentioning

confidence: 99%

Stress-dependent second-order grain statistics of polycrystals

Kube

Turner

2015

The Journal of the Acoustical Society of America

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In this article, the second-order statistics of the elastic moduli of randomly oriented grains in a polycrystal are derived for the case when an initial stress is present. The initial stress can be either residual stress or stresses generated from external loading. The initial stress is shown to increase or decrease the variability of the grain's elastic moduli from the average elastic moduli of the polycrystal. This variation in the elastic properties of the individual grains causes acoustic scattering phenomenon in polycrystalline materials to become stress-dependent. The influence of the initial stress on scattering is shown to be greater than the influence on acoustic phase velocities, which defines the acoustoelastic effect. This work helps the development of scattering based tools for the nondestructive analysis of material stresses in polycrystals.

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Section: Resultsmentioning

confidence: 99%

Stress-dependent second-order grain statistics of polycrystals

Kube

Turner

2015

The Journal of the Acoustical Society of America

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“…Thus, experimental data that do not appear to satisfy this assumption may ultimately be understood. Margetan et al 57 have shown the effects of multiple scattering in backscatter measurements for a strong scattering material. The present model can also predict the response for a pitch-catch scattering measurement setup where the transmitter and the receiver transducer are oriented at an angle relative to one another.…”

Section: Discussionmentioning

confidence: 99%

Wigner distribution of a transducer beam pattern within a multiple scattering formalism for heterogeneous solids

Ghoshal

Turner²,

Weaver

2007

The Journal of the Acoustical Society of America

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Diffuse ultrasonic backscatter measurements have been especially useful for extracting microstructural information and for detecting flaws in materials. Accurate interpretation of experimental data requires robust scattering models. Quantitative ultrasonic scattering models include components of transducer beam patterns as well as microstructural scattering information. Here, the Wigner distribution is used in conjunction with the stochastic wave equation to model this scattering problem. The Wigner distribution represents a distribution in space and time of spectral energy density as a function of wave vector and frequency. The scattered response is derived within the context of the Wigner distribution of the beam pattern of a Gaussian transducer. The source and receiver distributions are included in the analysis in a rigorous fashion. The resulting scattered response is then simplified in the single-scattering limit typical of many diffuse backscatter experiments. Such experiments, usually done using a modified pulse-echo technique, utilize the variance of the signals in space as the primary measure of microstructure. The derivation presented forms a rigorous foundation for the multiple scattering process associated with ultrasonic experiments in heterogeneous media. These results are anticipated to be relevant to ultrasonic nondestructive evaluation of polycrystalline and other heterogeneous solids.

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“…This is often found to be a reasonable assumption in practice, especially near the focal zone of a focused transducer, since multiple scattering events whose last scatter occurs outside of the sonic beam footprint are expected to generate very weak received signals. However multiple-scattering contributions can be significant in some circumstances, such as for larger grain sizes, inspections at higher frequencies, and depth zones not near the focal plane [9]. To better address the influence of multiple scattering, a "full scattering" model is under development by Ron Roberts of CNDE which accounts for all orders of multiple scattering [10].…”

Section: Figurementioning

confidence: 99%

Techniques and software tools for estimating ultrasonic signal-to-noise ratios

Chiou

Margetan

McKillip

et al. 2016

AIP Conference Proceedings

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Model-based software for simulating ultrasonic pulse/echo inspections of metal components AIP Conference Proceedings 1806, 150008 (2017) cchiou@iastate.edu Abstract. At Iowa State University's Center for Nondestructive Evaluation (ISU CNDE), the use of models to simulate ultrasonic inspections has played a key role in R&D efforts for over 30 years. To this end a series of wave propagation models, flaw response models, and microstructural backscatter models have been developed to address inspection problems of interest. One use of the combined models is the estimation of signal-to-noise ratios (S/N) in circumstances where backscatter from the microstructure (grain noise) acts to mask sonic echoes from internal defects. Such S/N models have been used in the past to address questions of inspection optimization and reliability. Under the sponsorship of the National Science Foundation's Industry/University Cooperative Research Center at ISU, an effort was recently initiated to improve existing research-grade software by adding graphical user interface (GUI) to become user friendly tools for the rapid estimation of S/N for ultrasonic inspections of metals. The software combines: (1) a Python-based GUI for specifying an inspection scenario and displaying results; and (2) a Fortran-based engine for computing defect signal and backscattered grain noise characteristics. The latter makes use of several models including: the Multi-Gaussian Beam Model for computing sonic fields radiated by commercial transducers; the Thompson-Gray Model for the response from an internal defect; the Independent Scatterer Model for backscattered grain noise; and the Stanke-Kino Unified Model for attenuation. The initial emphasis was on reformulating the research-grade code into a suitable modular form, adding the graphical user interface and performing computations rapidly and robustly. Thus the initial inspection problem being addressed is relatively simple. A normal-incidence pulse/echo immersion inspection is simulated for a curved metal component having a non-uniform microstructure, specifically an equiaxed, untextured microstructure in which the average grain size may vary with depth. The defect may be a flat-bottomed-hole reference reflector, a spherical void or a spherical inclusion. In future generations of the software, microstructures and defect types will be generalized and oblique incidence inspections will be treated as well. This paper provides an overview of the modeling approach and presents illustrative results output by the first-generation software.

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Looking for Multiple Scattering Effects in Backscattered Ultrasonic Grain Noise from Jet-Engine Nickel Alloys

Cited by 19 publications

References 6 publications

Stress-dependent second-order grain statistics of polycrystals

Stress-dependent second-order grain statistics of polycrystals

Wigner distribution of a transducer beam pattern within a multiple scattering formalism for heterogeneous solids

Techniques and software tools for estimating ultrasonic signal-to-noise ratios

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