Ultrasonic Attenuation in Polycrystalline Materials in 2D

Boström, Anders E; Ruda, Aurlia

doi:10.1007/s10921-019-0590-9

Cited by 11 publications

(5 citation statements)

References 11 publications

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“…However, this subject remains mostly unvisited for strongly scattering polycrystals. A few relevant studies include a recent two-dimensional theory showing applicability to materials of high anisotropy [26] and a theory for strongly scattering materials [27] and the references therein. However, for longitudinal waves, only a small difference is found in [27] from the Stanke and Kino model [5].…”

Section: Introductionmentioning

confidence: 99%

Finite-element and semi-analytical study of elastic wave propagation in strongly scattering polycrystals

et al. 2022

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This work studies scattering-induced elastic wave attenuation and phase velocity variation in three-dimensional untextured cubic polycrystals with statistically equiaxed grains using the theoretical second-order approximation (SOA) and Born approximation models and the grain-scale finite-element (FE) model, pushing the boundary towards strongly scattering materials. The results for materials with Zener anisotropy indices A > 1 show a good agreement between the theoretical and FE models in the transition and stochastic regions. In the Rayleigh regime, the agreement is reasonable for common structural materials with 1 < A < 3.2 but it deteriorates as A increases. The wavefields and signals from FE modelling show the emergence of very strong scattering at low frequencies for strongly scattering materials that cannot be fully accounted for by the theoretical models. To account for such strong scattering at A > 1, a semi-analytical model is proposed by iterating the far-field Born approximation and optimizing the iterative coefficient. The proposed model agrees remarkably well with the FE model across all studied materials with greatly differing microstructures; the model validity also extends to the quasi-static velocity limit. For polycrystals with A < 1, it is found that the agreement between the SOA and FE results is excellent for all studied materials and the correction of the model is not needed.

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Section: Introductionmentioning

confidence: 99%

Finite-element and semi-analytical study of elastic wave propagation in strongly scattering polycrystals

et al. 2022

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“…It is shown that the anisotropy factor, which is a combination of the elastic constants of the material, is representative of the degree of anisotropy and the models lose their accuracy for materials with a high anisotropy factor. On the other hand, Boström & Ruda [28] in two dimensions looked at the polycrystalline materials as a collection of individual grains in which each grain is considered to be surrounded by a matrix with the overall properties of all other grains (which is isotropic for equiaxed and randomly oriented grains). Using the explicit transition matrix for cubic materials presented by Boström [13], explicit expressions for the attenuation are derived for polycrystalline materials with cubic symmetry in two dimensions.…”

Section: Introductionmentioning

confidence: 99%

Scattering of elastic waves by a sphere with cubic anisotropy with application to attenuation in polycrystalline materials

2023

Self Cite

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Scattering of elastic waves by an anisotropic sphere with cubic symmetry inside an isotropic medium is studied. The waves in the isotropic surrounding are expanded in the spherical vector wave functions. Inside the sphere, the elastodynamic equations are first transformed to spherical coordinates and the displacement field is expanded in terms of the vector spherical harmonics in the angular directions and a power series in the radial direction. The governing equations inside the sphere give recursion relations among the expansion coefficients in the power series. The boundary conditions on the sphere then determine the expansion coefficients of the scattered wave. This determines the transition ( T ) matrix elements which are calculated explicitly to the leading order for low frequencies. Using the theory of Foldy, the T matrix elements of a single sphere are used to study attenuation and phase velocity of polycrystalline materials with cubic symmetry, explicitly for low frequencies and numerically for intermediate frequencies. Numerical comparisons of the present method with previously published results and recent finite element method (FEM) results show a good correspondence for low and intermediate frequencies. The present approach shows a better agreement with FEM for strongly anisotropic materials in comparison with other published methods.

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“…The current research found that when ultrasonic vibration acts on the solid medium, the absorption and scattering of ultrasonic by the material will cause the loss of ultrasonic energy, and the ultrasonic intensity gradually attenuates with the increase of propagation distance [21,22]. However, this kind of effect has been not considered in the existing research and analysis.…”

Section: Introductionmentioning

confidence: 99%

Effect of ultrasonic attenuation characteristics on forming accuracy of ribbed cylindrical parts in ultrasonic-assisted spinning process

Li,

Zhu,

Zhao

et al. 2023

Preprint

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Ultrasonic-assisted forming process is one of the important methods to improve the formability of materials because of its acoustic softening effect and antifriction effect. After the introduction of ultrasonic, the forming accuracy of the inner ribs is improved in the spinning process of ribbed cylindrical parts, but the effect law of ultrasonic energy on the forming of inner ribs have not been clarified in detail. In this paper, a modeling method of ultrasonic-assisted spinning was proposed, which was taken into account the attenuation characteristics of ultrasonic energy in solid media for the improvement of the simulation accuracy. The corresponding simulation model was established to explore the effect law of ultrasonic amplitude on the forming accuracy of inner ribs. The results showed that the forming height and surface morphology of longitudinal ribs can be improved effectively in the ultrasonic-assisted spinning process. With the increase of ultrasonic amplitude, the forming height of longitudinal rib gradually increased, but the increase degree gradually slowed down, and the surface morphology of the longitudinal ribs always present the geometric characteristics that the screw-in end is higher than the screw-out end. The reason is that the application of ultrasonic vibration promoted the radial and circumferential flow of the material, and improved the material filling ability into the rib groove. The combined effect of ultrasonic softening effect and anti-friction effect reduced the radial filling difference between the screw-in end and the screw-out end of the ribs. Ultrasound could enhance the material flow but did not significant change the forming distribution characteristics of the ribs, resulting in limited rib height and uneven surface morphology. Also, the energy field gradient design method along the sheet thickness was proposed to further improve the forming accuracy of the inner ribs.

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Ultrasonic Attenuation in Polycrystalline Materials in 2D

Cited by 11 publications

References 11 publications

Finite-element and semi-analytical study of elastic wave propagation in strongly scattering polycrystals

Finite-element and semi-analytical study of elastic wave propagation in strongly scattering polycrystals

Scattering of elastic waves by a sphere with cubic anisotropy with application to attenuation in polycrystalline materials

Effect of ultrasonic attenuation characteristics on forming accuracy of ribbed cylindrical parts in ultrasonic-assisted spinning process

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