A novel instrument for transient photoelasticity

A new instrument has been developed for the photoelastic analysis of transient events. The instrument is based on the Phase-Stepped Images Obtained Simultaneously (PSIOS) system developed by Patterson and Wang, which enables four phase-stepped photoelastic images to be collected simultaneously. Where the new instrument differs is that the original instrument requires four cameras to collect the four images, whereas the new instrument requires only one camera. This makes the use of phase-stepping viable for events, in which the fringe order varies with time. Three examples are given of the use of the instrument in static and dynamic photoelasticity to generate full field maps of isochromatic fringes. The instrument has been found to work well and significantly increases the potential for the use of photoelasticity to study transient and possibly dynamic events.