Ultrasonic evaluation of dynamic strain, crack nucleation, and growth

Abstract

The method proposed is a further development of an earlier work described by Hazony et al. [‘‘Ultrasonic monitoring of tensile, fatigue, or creep specimens in situ,’’ 2279(A) (1993)]. Two transducers are imbedded at the front and back faces of the specimens along the principal axis. These transmit and receive arbitrarily sharp stress pulses that probe both the volume and the surface of the specimen. The respective times of flight are sufficient for the monitoring of longitudinal and transversal strains. Moreover, intensity tracking of the various received acoustic signals also serves well for monitoring onset and growth of cracks. Sensitivity and calibration issues will be discussed and experimental data on high-strength low-alloy steel and other alloy specimens will be presented. The method lends itself to high precision measurements of material deformation and damage and may be used at high temperatures and in aggressive environments. [Work supported by ONR and TecSonics, Inc. of Twinsburg, Ohio.]