Parallax error correction of a multilens camera for precise determination of dynamic stress intensity factor

To improve the accuracy in caustic measurement, the effect of parallax with 30 lenses of a Cranz-Schardin-type camera on the determination of caustic diameter D was experimentally evaluated using a single-edge-notch-type model specimen. Correction factors for the transverse diameter of caustics on an image plane were obtained. These factors were taken into account in the determination of the velocity effect on the dynamic stress intensity factor K ID of PMMA during fast crack propagation. It is shown that the hysteresis in the K ID -\dot a curves was similar for larger and smaller initial curves except at velocities higher than 400 m/s.