Stress Optical Coefficient

Stress optical coefficient is a value that characterizes the stress experienced from the results of measurement of stress birefringence.

Stress Optical Coefficient Measurement Procedure

The stress-optical coefficient of glass, which is utilized in photoelastic studies, can be found using the ASTM C770 test method. For a glass fiber subjected to uniaxial tension, Procedure A determines the optical retardation. Procedure B measures the optical retardation for a rectangular glass beam that has undergone four-point bending. In step C, a rectangular-cross-section glass beam is compressed uniaxially, and the optical retardation is measured.

Conditions for Stress Optical Coefficient Test:

The stress optical coefficient K for ASTM C770 is computed at a wavelength of 0.5893 m and a temperature of 21°C. The measurement precision is 0.0610-6 mm²/N, or 3%.

Data:

n = refractive index.

E = Young’s modulus.

µ = Poisson number.

Common Uses of Stress Optical Coefficient Test:

To estimate the size of residual thermal stresses for pre-stressing (tempering) or annealing glass, ASTM C770 is helpful. 

When a rectangular glass beam is subjected to uniaxial tension, four-point bending, and uniaxial compression, this standard test procedure can be used to determine optical retardation.