title: Simulation of incoherent and coherent backscattered wave fields from cavities in a solid matrix.
abstract: This paper reports a study of the backscattered ultrasonic signal from a solid layer containing spherical cavities, to determine the conditions in which an effective medium model is a valid description of the response. The work is motivated by the need to model the response of porous composite materials for ultrasonic non-destructive evaluation (NDE) techniques. The numerical simulation predicts the response of a layer containing cavities at a single set of random locations, and compares it to the predicted response from a homogeneous layer with ensemble-averaged material properties (effective medium model). The study investigates the conditions in which the coherent (ensemble-averaged) response is obtained even from a single configuration of scatterers. Simulations are carried out for a range of cavity sizes and volume fractions. The deviation of the response from effective medium behavior is modeled, along with the trends as a function of cavity radius, volume fraction, and frequency, in order to establish an acceptability criterion for application of an effective medium model.
authors.affiliation: Electrical Systems and Optics Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom. v.pinfield@lboro.ac.uk
authors.forename: Valerie J
authors.initials: VJ
authors.lastname: Pinfield
authors.forename: Richard E
authors.initials: RE
authors.lastname: Challis
mesh_terms: D003198:Computer Simulation; D008962:Models, Theoretical; D009038:Motion; D009716:Numerical Analysis, Computer-Assisted; D016062:Porosity; D012542:Scattering, Radiation; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013997:Time Factors; D014465:Ultrasonics / Q000379:methods*