Strength Tests Of Flat Glass By Means Of Four-Point Bending

The strength of flat glass, especially of tempered or heat-strengthened flat glass, can be determined by means of the four-point bending method according to a German standard. The strength of a specimen is defined as the tensile stress in ints central part at failure, and this failure stress is calculated using the Bernoulli beam bending theory. However, the basic conditions of this theory are not fulfilled in the experiments. Deviations from the method of 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.