This standard specifies the principle, specimens, instruments, procedure, calculation method and report content, etc. of the stress examination of glassware.
This standard is applicable to the stress examination of glassware after annealing.
2 Principle
Generally, glass is isotropic homogeneous material, where there is stress, it will show anisotropy, and optical birefringence will be generated, and the relationship between the birefringence optical path difference ΔS and stress is:
ΔS=Kσ·d (1)
Where,
ΔS-the birefringence optical path difference;
σ-the difference between two principal stresses vertical to the optical propagation direction, N/mm2;
K-the stress optical constant of glass, 10-6mm2/N;
d-the optical path length (thickness) in glass specimen, cm.
The stress optical constant K of the same type of glass is the same, thus its stress may be represented by the optical path difference of unit thickness. This standard specifies the measurement method in which polarization stress gauge is used for measuring optical path difference and the product stress is represented by the value of optical path difference unit thickness.
3 Specimen
GB/T 15726-1995 The following standards are cited：
