Computational Study of Grain Scattering Effects in Ultrasonic Measurements

Abstract

A two-dimensional scalar model has been established to study the scattering caused by an inhomogeneous medium with granular microstructure. Time domain signals are calculated using a 64-node PC cluster. Special test problems are set up to compare the effects of single and multiple scattering and to quantify errors introduced by the Born approximation. Computed results for backscattered RMS grain noise results are compatible with recent experimental measurements.

Ultrasonic attenuation in polycrystals using a self-consistent approach

“…In this scope, the SC model is expected to be a more suitable foundation from which more complicated models could be based, e.g., models accounting for grain elongation, macrotexture, grain size gradients, multiphases, defects, etc. Many of these more complicated microstructures have already been theoretically addressed using Voigt averages [38][39][40][41][42][43]. The present SC theory can be easily implemented by simply including the anisotropy coefficient γ and self-consistent elastic moduli C SC .…”

Ultrasound scatter in heterogeneous 3D microstructures: Parameters affecting multiple scattering

“…This algorithm allows for the prediction of backscattered grain noise responses by solving for the displacement field in an explicitly defined heterogeneous medium. This algorithm has been used to study twodimensional scalar problems [3], two-dimensional elastic problems [4], and most recently three-dimensional elastic problems [5]. The three-dimensional work considered only single realizations of microstructure, which is inconsistent with the approach typically taken in the laboratory where hundreds of realizations are sampled by scanning the transducer over the sample [1].…”

A Study of Effects of Tissue Inhomogeneity on HIFU Beam

“…We used approach described in [3,4] For small c(x) inhomogeneity (< 5% variation), this can be solved as Neumann series and can be efficiently computed using FFT. For simulation of tissue layers (muscle and liver), each pixel c ij has random velocity value of magnitude ε where c ij = c 0 (1 + ε r), -1 < r < 1 , ε = 0, .01, .03; r is random number with uniform probability.…”

“…Researchers including Thompson and Roberts (co-authors) recently studied the effects of phase aberration on ultrasound focusing in aerospace engine materials such as titanium alloy, and have developed a computational model to examine these effects [3,4]. The ultrasound beam observed after transmission through the fused quartz (homogeneous) and that observed after transmission through the titanium (inhomogeneous) demonstrate the severe beam wavefield amplitude distortion introduced by the velocity inhomogeneity-induced phase aberration (Fig.…”