Strength tests of flat glass by means of four-point bending

Abstract

The strength of flat glass, especially of tempered or heat-strengthened flat glass, can be determined by means o f the four-point bending method according to a German standard. The strength of a specimen is defined as the tensile stress in its central part at failure, and this failure stress is calculated using the Bernoulli beam bending theory. However, the basic conditions o f this theory are not fulfilled in the experiments. Deviations from the method o f evaluation, as specified in the standard, are pointed out in this paper using a nonlinear theory of shells; the numerical calculations were confirmed by experiments.