Conventional mentality and new findings in plate glass (Part 1) — Stress relaxation phenomena and fracture —

Glass strength in plate glass was measured using the Quasi-static method to investigate its mechanical properties. New findings concerned with stress relaxation phenomena being generated at once after loading and time dependent fracture were seen even at room temperature. Load reduction phenomenon at room temperature has gone unnoticed for many years, because its value was 2–4.5 N in Caustics method, although measurement error approximately was 5 N in ordinary 4-point bending test method. Fracture in plate glass was inferred to be caused not only by applied stress to glass but also through complex behavior involving several factors. The concept of stress relaxation phenomenon under strain points that do not occur or occur over a lengthy period of several decades at least will be necessary to reconsider. Almina ceramics showed fracture characteristics closer to plate glass than silicon carbide which also called a ceramics.