Advanced ultrasonic for remaining life assessment of industrial components

Abstract

Nonlinear ultrasonic is the new approach for the effective evaluation of material degradation in the area of nondestructive evaluation (NDE). Fatigue damage of a material produces a substantial distortion ofultrasonic waves propagating through the degraded material. The wave distortion is quantified by means of a material nonlinearity parameter f3 that is defused as the ratio ofthe amplitude of the 2nd harmonic to the square of the amplitude of the fundamental. This nonlinear parameter changes when, for instance, a distribution ofmicrocracks appears inside the material. This feature has recently been found as a new potential application in the characterization of fatigued and degraded materials. In this present paper, the potential of NLU technique to evaluate fatigue damage in structural steel and to assess the localized plastic deformation during high cycle fatigue to locate the position of crack initiation much before the failure along the gage length of hourglass type specimen in polycrystalline copper has been highlighted.