An arctangent unwrapping technique of photoelasticity using linearly polarized light at three wavelengths

摘要

In the automatic measurements of the principal stress directions Ψ and the total relative phase retardation ρ{sub}(tol) Ψ andρ{sub}(tol) can be easily obtained by the phase unwrapping method using the arctangent function. However, only some published works exist on the measurements of Ψ andρ{sub}(tol) by photoelastic techniques using a linearly polarised incident light source. This paper presents the technique of applying an unwrapping by means of the arctangent function to photo elasticity. The technique overcomes the error associated with the quarter wave plate by using an incident light of different wavelength and does not need an interpolation for the determination of Ψ. The technique is validated by determining Ψ andρ{sub}(tol) for the well-known circular disk subjected to a diametral compressive load model.