Abstract (Invited)

Ultrasonic Characterization of the Nonlinear Elastic Properties of Materials

R.E.Green Jr. (Center for Nondestructive Evaluation, Johns Hopkins University, Baltimore, MD, USA)

e-mail: robert.green@jhu.edu

Even though many of the characteristics of elastic wave propagation in materials have been known for years, others have still not been determined. This is complicated by the fact that over the past several decades many new materials and combinations of materials, e.g. composites, have been developed. The characteristics of low-amplitude linear elastic waves are understood much better than those associated with nonlinear elastic waves. Moreover wave propagation in materials which are assumed to be homogeneous and isotropic is also better understood than in more realistic inhomogeneous, anisotropic materials. This paper will summarize the nonlinear effects associated with elastic wave propagation in these more realistic materials. Examples will be given of materials, which in their undeformed state behave in a linear elastic fashion, but behave in a nonlinear elastic fashion when infinitesimal elastic waves are propagated provided that an external stress is superimposed or has been previously applied, materials where the amplitude of the wave is sufficiently large that finite nonlinear elastic strains arise and materials which are inherently nonlinear or contain inhomogenieties such that they are locally nonlinear.

Section : 3