GB/T 15726-1995 in English

《GB/T 15726-1995玻璃仪器内应力检验方法》由TC178（全国玻璃仪器标准化技术委员会）归口，主管部门为中国轻工业联合会。
本标准规定了玻璃仪器内应力检验的原理、试样、仪器、程序、计算方法、报告内容等。本标准适用于退火后的玻璃仪器内应力检验。

1 Subject Content and Application Scope

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

1 Subject Content and Application Scope
2 Principle
3 Specimen
4 Instruments
5 Examination Procedure
6 Representation Method of Examination Result
7 Examination Report