Interactive control for an automatic polariscope

Abstract

The problems of interpreting and analysing photo‐elastic data have deterred non‐specialists from making use of this technique when undertaking detailed design studies. Practical difficulties in understanding complex fringe patterns and in making the necessary optical measurements with sufficient precision have implied that considerable experience is necessary to obtain reliable stress values at internal points or across critical sections.By interconnecting two minicomputers it has been possible to develop an interactive polariscope control system which will allow the design engineer, with minimal prior knowledge of photoelastic techniques, to employ relatively sophisticated methods for evaluating the stresses in both two and three dimensional models. The data acquisition sequence involves new procedures for determining both the isoclinic angle and the isochromatic fringe number, and the interactive nature of the control system allows the desired analysis to proceed in response to the replies to a series of simple questions posed by the machine.The application of the system will be illustrated by examples of its use to determine boundary stresses at critical locations, where the high stress gradient presents problems, and in evaluating the separate stress components across the critical section of a grooved cylindrical rod.