Nondestructive flaw detection in a solid medium using nonlinear acoustic effects

Abstract

In a solid material it is very difficult to find tiny defects or cracks with the conventional linear acoustic techniques as nondestructive evaluation methods. When defects exist in a material, nonlinear acoustic responses become dominant in a propagating medium and can make it possible to detect such defects. As an application of such nonlinear acoustics, a nonlinear acoustic modulation technique for nondestructive flaw detection described in previous work [Kim et al., J. Acoust. Soc. Am. 101, 3029 (1997)] was applied to several different sample materials to confirm its feasibility. The second harmonic measurements can easily indicate existence of tiny defects or cracks in the samples. The time-delay measurements of the modulated sum and difference frequency signals can accurately locate defects in aluminum, steel, and brass solid rods, respectively.