Studies in Dynamic Photoelasticity

Equipment and techniques are described for obtaining dynamic photoelastic stress patterns from arbitrary lines in plane-stress systems by means of streak photography. Streak-type stress patterns of such lines were obtained which provide continuous records throughout the entire period of impact (of the order of milliseconds) at times of exposure of 2/3 microsec. This is thirty times faster than the time of exposure (20 microseconds) obtained by Tuzi and Nisida in 1935. Dynamic photoelastic stress patterns showing stress-wave propagation are given for a bar struck axially by a rigid mass, and these patterns show that a uniform state of stress was obtained. Theoretical stress patterns based on the Boussinesq solution are in essential agreement with the experimental results.