Theoretical Studies in Nondestructive Evaluation (NDE)
Abstract
A previously developed technique has been use to describe the discrete scattering of scalar waves from defects on a regular simple cubic lattice. The method makes no assumption about the symmetry of the scatterers and therefore can be applied to inhomogeneities of arbitrary shape. The only limitation of the technique is the maximum number of defects one can use to specify the scatter, which in turn is determined by limitations in computation time. The multiple scattering model proposed by Foldy and later extended by Lax was implemented by West and Shlesinger as a means of evaluating the distribution of grains in polycrystalline materials. If the material consists of grains such that the wavelength is much larger than the grain size then the density of scatterers probed by the acoustic wave is unchanged as the frequency is increased, provided that one remains in the Rayleigh scattering domain. If one is in the scattering domain where the wavelength is less than or equal to the grain size, then the density of scatterers increases no more rapidly than the square of the linear scale (a-squared) rather than as its cube as it would in the usual situation. This implies that the density of scatterers is a fractal in the stochastic scattering domain. Note also that the surface of a grain can have many scales and may in part be responsible for the fractal behavior observed in the phenomenological expression. Keywords: Scattering theory, The Fractal Dimension of Ultrasonic Scatters.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1985
- Accession Number
- ADA159155
Entities
People
- Bruce J. West