ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

4pEA14. Nonlinear combinational sound scattering by discontinuity-like defects in solids and its possible usage for crack diagnostics.

I. Yu. Belyaeva

V. Yu. Zaitsev

Inst. of Appl. Phys., 46 Uljanova str., Nizhny Novgorod, 603600, Russia

One of the important problems in structural control of solids is the problem of discontinuity-like defects diagnostics. The main drawback of conventional linear diagnostic methods is the complicated differentiation between a weak ``useful'' signal originated due to a crack and the waves scattered by other inhomogeneities of the material, which are not interesting from the viewpoint of flaw detection. In view of this problem, new acoustic diagnostic methods based on measuring nonlinear acoustic characteristics have recently begun to attract the attention of researchers. The effect of acoustic waves scattering nonlinearly from a thin discontinuity-like defect in a solid is analyzed. The defect is considered as the interface between two surfaces covered with bulges characterized by different initial deformation. It is shown that the nonlinear scattering into combinational-frequency waves is much more sensitive to the loading of the interface contacts compared with the scattering into the wave of fundamental frequency. The observation of nonlinear scattering by crack-type defects should allow one to distinguish cracks from other scatterers and can be used for creation of new methods of crack detection and positioning.