Model of the failure of steel under conditions of stress concentration

Abstract

The article explains notions concerning the nature of the brittleness of steel connected with the action of stress raisers. It shows that the embrittling effect of stress raisers is connected with their bringing about a three-dimensional state of stress and strain concentration. It substantiates the advantage of using as measure of ductility of metal the coefficient of ductility K_d determined as the ratio of the “brittle” strength of the metal (resistance to microcleavage R_mc) to the yield strength σ_y. This approach is applied to the cold brittleness of a product containing constructional stress raisers. It was established that this phenomenon takes place when the ductility of the metal lies below some limiting K_dc whose magnitude is determined by the parameters of the state of stress and strain and by the proneness of the metal to strain-hardening. On the example of α- iron of carbon steels it is shown that the suggested approach can be used for predicting the temperature of cold brittleness under conditions of stress concentration.