A simple statical approach to the measurement of the elastic constants in anisotropic media

M. Hayes

doi:10.1007/bf00555041

FEA-Based Ultrasonic Focusing Method in Anisotropic Media for Phased Array Systems

Applied Sciences ◽

10.3390/app11198888 ◽

2021 ◽

Vol 11 (19) ◽

pp. 8888

Author(s):

Seongin Moon ◽

To Kang ◽

Soonwoo Han ◽

Kyung-Mo Kim ◽

Hyung-Ha Jin ◽

...

Keyword(s):

Wave Propagation ◽

Ultrasonic Wave ◽

Elastic Constants ◽

Grain Orientation ◽

Phased Array ◽

Ultrasonic Imaging ◽

Anisotropic Media ◽

Imaging Method ◽

Ultrasonic Wave Propagation ◽

Propagation Paths

Traditional ultrasonic imaging methods have a low accuracy in the localization of defects in austenitic welds because the anisotropy and inhomogeneity of the welds cause distortion of the ultrasonic wave propagation paths in anisotropic media. The distribution of the grain orientation in the welds influences the ultrasonic wave velocity and ultrasonic wave propagation paths. To overcome this issue, a finite element analysis (FEA)-based ultrasonic imaging methodology for austenitic welds is proposed in this study. The proposed ultrasonic imaging method uses a wave propagation database to synthetically focus the inter-element signal recorded with a phased array system using a delay-and-sum strategy. The wave propagation database was constructed using FEA considering the grain orientation distribution and the anisotropic elastic constants in the welds. The grain orientation was extracted from a macrograph obtained from a dissimilar metal weld specimen, after which the elastic constants were optimized using FEA with grain orientation information. FEA was performed to calculate a full matrix of time-domain signals for all combinations of the transmitting and receiving elements in the phased array system. The proposed approach was assessed for an FEA-based simulated model embedded in a defect. The simulation results proved that the newly proposed ultrasonic imaging method can be used for defect localization in austenitic welds.

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Finsler metric and elastic constants for weak anisotropic media

Nonlinear Analysis Real World Applications ◽

10.1016/j.nonrwa.2011.05.018 ◽

2011 ◽

Vol 12 (6) ◽

pp. 3177-3184 ◽

Cited By ~ 5

Author(s):

Takahiro Yajima ◽

Kazuhito Yamasaki ◽

Hiroyuki Nagahama

Keyword(s):

Elastic Constants ◽

Anisotropic Media ◽

Finsler Metric

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Estimation of elastic constants for HTI media using Gauss-Newton and full-Newton multiparameter full-waveform inversion

Geophysics ◽

10.1190/geo2015-0594.1 ◽

2016 ◽

Vol 81 (5) ◽

pp. R275-R291 ◽

Cited By ~ 56

Author(s):

Wenyong Pan ◽

Kristopher A. Innanen ◽

Gary F. Margrave ◽

Michael C. Fehler ◽

Xinding Fang ◽

...

Keyword(s):

Elastic Constants ◽

Order Term ◽

Fractured Reservoirs ◽

Waveform Inversion ◽

Anisotropic Media ◽

Second Order ◽

Full Waveform Inversion ◽

Full Waveform ◽

Fractured Medium ◽

Hti Media

In seismic full-waveform inversion (FWI), subsurface parameters are estimated by iteratively minimizing the difference between the modeled and the observed data. We have considered the problem of estimating the elastic constants of a fractured medium using multiparameter FWI and modeling naturally fractured reservoirs as equivalent anisotropic media. Multiparameter FWI, although promising, remains exposed to a range of challenges, one being the parameter crosstalk problem resulting from the overlap of Fréchet derivative wavefields. Parameter crosstalk is strongly influenced by the form of the scattering pattern for each parameter. We have derived 3D radiation patterns associated with scattering from a range of elastic constants in general anisotropic media. Then, we developed scattering patterns specific to a horizontal transverse isotropic (HTI) medium to draw conclusions about parameter crosstalk in FWI. Bare gradients exhibit crosstalk, as well as artifacts caused by doubly scattered energy in the data residuals. The role of the multiparameter Gauss-Newton (GN) Hessian in suppressing parameter crosstalk is revealed. We have found that the second-order term in the multiparameter Hessian, which is associated with multiparameter second-order scattering effects, can be constructed with the adjoint-state technique. We have examined the analytic scattering patterns for HTI media with a 2D numerical example. We have examined the roles played by the first- and second-order terms in multiparameter Hessian to suppress parameter crosstalk and second-order scattering artifacts numerically. We have also compared the multiparameter GN and full-Newton methods as methods for determining the elastic constants in HTI media with a two-block-layer model.

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