Processing of glasses with engineered stress profiles

Abstract The introduction of a compressive residual stress with a maximum below the glass surface can promote the stable growth of surface flaws and result in high strength value with limited scatter. Such approach has been reduced to practice in recent years using a double ion-exchange process. Obtained glasses have been named as engineered stress profile (ESP) glasses to emphasize the engineering design approach. In the present work, an alternative production technique, based on physical processes to obtain the specific residual stress profile in soda-lime silicate glass is presented. The proposed technique consists of a conventional physical tempering followed by a fast heating treatment necessary to relax the compressive stress on the surface only. Such relaxation is produced by rapid treatment in a fused tin bath. ESP glasses produced in this manner are compared in terms of residual stress profile, mechanical strength and failure behaviour.