The Effect of Sustained Loading on the Breaking Strength of Sheet Glass

JSGT 1940 V24 T046-T057

 The effect of sustained loading on the modulus of rupture of specimens of sheet glass having ground and well-polished edges and of dimensions 10 X 0.8 X 0.275 cm has been determined by loading the specimens to the extent of 100, 90, 80, 70, 60, 50, 40 and 30 per cent of the previously determined mean breaking load and measuring the time interval between loading and fracture. For loads equal to or greater than 70 per cent a number of specimens fractured before the full load was reached. For loads less than 70 per cent some of the specimens remained unbroken after 1000 hours, the number unbroken increasing as the load decreased until all the specimens remained unbroken after 1000 hours at the 30 per cent load. For those specimens fracturing it was found that a straight-line relationship held between the logarithm of the mean breaking time and the logarithm of the applied stress. A factor of safety of not less than four was suggested for sheet glass of the type described.

A. J. Holland, M.Sc., Ph.D., A.R.C.S., D.I.C., and Professor W. E. S. Turner