Volume 18, Issue 1 (January 1990)
Dynamic K Measurements in Three-Point-Bend Specimens
The displacement across the tip of a crack in a three-point-bend specimen loaded in a drop tower was measured with inplane laser interferometry. The equivalent displacement was measured in a statically loaded specimen; the two measurements were combined to produce a dynamic load-time plot. This result is used to compute the stress intensiy factor, K, under dynamic loading. It is compared with an equivalent plot obtained from foil gages at the quarter-points of the specimen. The K based on near-tip measurements is initially higher than the one based on the far-field loads, but the two records agree after approximately 0.5 ms. This transition time, before which inertial and wave propagation effects are important, is in close agreement with recent predictions by others.