Theory of the photoelastic biaxial strain gauge

Abstract

An annular disk of photoelastic material, with a reflective backing, when bonded around its periphery to the surface of a body subsequently subjected to strain, forms a biaxial strain gauge when observed by a reflection polariscope. The birefringence demonstrated by the disk identifies major and minor principal strains both in magnitude and direction. Mathematical solutions for the calibration characteristics of such a gauge are described, for biaxial strains in tension. Close agreement exists between the theoretical sensitivity and that determined by experiment, previously reported.