On the Mechanics of Grey Cast Iron Under Pure Bending

This paper presents the results of experiments conducted on lamellar graphite grey cast iron of rectangular section subjected to pure bending. Strain measurements confirm the traditional speculation that plane sections remain plane under strain. Owing to the nonlinear relationship between stress and strain, however, the neutral axis of a loaded specimen is shown to shift away from the centroidal axis. This shift is evidently amplified with increased loading. A computer program is herein specially devised for calculating the shift in neutral axis through satisfaction of the conditions of equilibrium together with checking for possible crack initiation at the extension side. While the simple flexural formula holds very nearly true for the compression side, it fails, however, to predict stresses on the extension side, the situation being further aggravated by higher bending moments. The apparent high bending strength of grey cast iron is fully accounted for.