In scattered-light photoelasticity with unpolarized light, the secondary principal stress direction ψ and the relative phase retardation ρ in a three-dimensional stressed model with rotation of the principal stress axes can be obtained by use of Stokes parameters. For completely automated stress analysis, measurements of the total relative phase retardation and the secondary principal stress direction over the entire field are required, and it is necessary to unwrap ψ and ρ. A phase unwrapping method is thus proposed for the determination of these values based on scattered-light photoelasticity. The values are easily obtained via an arctangent function, overcoming the error associated with the quarter-wave plate by employing an incident light of different wavelengths. The proposed technique provides automated and nondestructive determination of the total relative phase retardation and the secondary principal stress direction in a model exhibiting rotation of the principal stress axes.
© 2006 Optical Society of America
Original Manuscript: April 12, 2006
Manuscript Accepted: August 9, 2006
Toshiki Kihara, "Phase unwrapping method for three-dimensional stress analysis by scattered-light photoelasticity with unpolarized light," Appl. Opt. 45, 8848-8854 (2006)