The role of nonlinear ultrasound in the diagnosis of early-stage damage in heterogeneous materials

Abstract

Predictable noninvasive evaluation of engineering materials requires a more reliable sensing technique capable of providing quantitative information of early stage damage. Nonlinear ultrasound (NLU) is a promising candidate because it provides a direct measure of the nonlinear elastic behavior of materials. NLU excels in the direction and quantification of damage that originates at or beneath the material’s microscale. This talk will present a procedure for the second harmonic generation (SHG) measurements using nonlinear Rayleigh surface waves. This technique quantifies material nonlinearity through the acoustic nonlinearity parameter, β. Specifically, microscale material characterization of physical/chemical phenomena in heterogeneous materials will be reviewed by means of the acoustic nonlinearity parameter, β. The results reveal how the SHG technique can provide the quantitative relationship between the acoustic nonlinearity parameter and the damage state of these materials. Last, new strategies for the application of the SHG technique will be discussed with an emphasis on bio-engineering materials and rocks.