Residual Stress Measurement in Ion-Exchanged Glass by Iterated Birefringence and Etching

Abstract

Residual stresses play an important role in controlling fracture behavior in ion-exchanged glass. In this work, the internal tensile stress resulting from ion exchange is measured using conventional birefringence methods. By progressively etching thin layers from the glass surface, the compressive stress in the removed layer can then be determined from the change in the compensating internal tensile stress, producing a stress profile as a function of depth. Specimen geometry, surface roughness, and configuration of the optical system are examined in order to improve the accuracy of the method.

Gradient scattered light method for non-destructive stress profile determination in chemically strengthened glass

“…Equation (24) was formulated in such a way by Brodland and Dolovich [34] in order to produce symmetric, self-equilibrating stress distributions, like those that typically arise in a uniformly strengthened glass plate, for specimens that extend from y = 0 to y = 2D. Stress equilibrium through the thickness is granted:…”

“…We suggest replacing the measurement of central core tensile stresses with gradient scattered light method instead of currently used transmission photoelasticity [24] or originally used scattered light method [11]. Each time when a layer with thickness of 1-2 lm is etched away using HF acid the alternation of full stress profile is induced.…”

“…In order to achieve increased accuracy, Abrams et al [24] replaced the scattered light measurement with transmission photoelasticity for central tension measurement in the Bradshaw's method. Sglavo et al [12] introduced curvature measurements for determining the stress profile in chemically strengthened glass.…”

“…Two separate fringe patterns are recorded-one for the extraordinary ray (also referred to as TM-wave) and other for the ordinary ray (TE-wave). The DSR method presented by Kishii [13] assumes that the stress profile is linear, which makes it unsuitable for measuring stress profiles with complex shape encountered in chemically strengthened lithium aluminosilicate glass or double ion-exchanged [24][25][26][27] glass. The method of surface refractometry can be considered as indirect measurement because no info is gathered from specific depth, but it relies on analysis of fringe pattern produced by resurgent light.…”

Prediction of crack propagation and fracture in residually stressed glass as a function of the stress profile and flaw size distribution

“…17 As-received plates were cut to dimensions of 100 mm × 50 mm, and polished to improve optical transmission, then processed in the ion exchange salt baths, producing a compressive surface stress and a compensating internal tensile stress. The tensile stresses in the interior of each specimen were measured using conventional optical retardation techniques.…”