Abstract
An achromatic quarter-wave plate was used to determine the principal-stress directions from color photoelastic fringes obtained in a diffuse light semicircular polariscope, which was composed of a plane polariscope with a quarter-wave plate. Four phase-shifted photoelastic fringe images were acquired using the polariscope, and used to obtain the wrapped principal-stress direction using a phase-shifting technique. To investigate the effectiveness of the quarter-wave plate in the polariscope, the principal-stress directions from color photoelastic fringes of a circular disk subjected to a concentrated load were determined, and compared with those obtained in a parallel light semicircular polariscope. Results showed that the achromatic quarter-wave plate in the diffuse light semicircular polariscope was effective.
