Evaluation of residual stress distribution inside a tempered thick glass plate using photo-elastic modulator

摘要

Glass is well-known example a brittle material. In many products made i)f glass. such automobile windshields and glass panels for flat-screen TV-tubes, high compressive residual stresses are often induced artificially at the surface in an attemptto avoid incidental fracture. Residual stress in a glass sheet arises due to the temperature gradient during rapid cooling across the transition range. When those products are subjected to large external forces, the superposition of the induced residualstress can sometimes result in a dangerous situation. Although very high compressive residual stresses are induced into the latest flat-screen TV-tubes to confer a high withstand strength in the face of external pressure caused by the vacuum inside, it is sometimes difficult to measure and estimate the safety limits of the residual stresses. It is, therefore, very important to he able to accurately and quantitatively measure such residual stresses inside glass products. The current non-contact method for measuring residual stresses uses transmitted or scattered photoelasticity and total reflection for this purpose. In this study, the authors adopt a system based on a Photo-Elastic Modulator (PEM) to evaluate the distribution (if redidual stresses at thesurface and inside a tempered thick glass plate.