Evaluation of the IRAD Flexible Probe Sonic Extensometer

Abstract

Evaluation of the IRAD sonic extensometer was initiated with an electronic-circuit analysis which indicated an accuracy of +/- 0.001 in. (0.025 mm). Readings from two sonic probes consistently were low by 2% for distances between magnetic anchors, but were accurate to +/- 0.002 and +/- 0.003 in. (0.051 and 0.076 mm) for small displacements. Although a series of high explosive tests subjected magnetic anchors to peak accelerations of from 2,100 g to 32,000 g the anchors generally did not experience detectable damage. Sonic probe readings exhibited a sensitivity to temperature changes with two of the four segments monitored exceeding the correction factor cited by the manufacturer.