Effects of yielding on stress maxima in semi-brittle bending specimens

The current investigation presents a method for estimating the actual stress maximum in flexure specimens following the onset of plastic deformation based on the elastically calculated stress maximum and the uniaxial elastic-plastic behavior. It is shown that for materials exhibiting an approximately bilinear uniaxial deformation relation this difference is a function of the ratio of the hardening rate to Youngʹs modulus while yield stress plays no decisive role. Results further indicate that this method applies equally well to three or four point flexure specimens that either are unnotched or contain a round, straight-through notch. Values calculated by this method are in good agreement with values determined using an extensive finite element analysis and with data calculated using plasticity theory. Good correlation is also seen between stress and strain maxima as calculated here compared with data measured experimentally.