Three dimensional elastic-plastic finite element modelling of small fatigue crack growth under a single tensile overload

Abstract

The effects of a single tensile overload on the stress, strain and displacement fields for a three dimensional semi-circular extending crack have been studied using an elastic-plastic finite element model. The results show that the application of a single tensile overload caused an immediate drop in the crack opening stress levels, but with further crack extension the opening stress levels rapidly rose to values higher than those before the application of the overload. It is found that the introduction of a single tensile overload increases the local residual compressive stress ahead of the crack front and, with the growth of the crack, the magnitude of this local compressive stress decreases. The results also show that the introduction of a single tensile overload increases the crack opening displacement, and that with further crack extension the crack opening displacement decreases rapidly to a value less than that before the application of the overload. The predicted crack opening displacements from finite element analysis were compared with those measured from direct in-situ SEM observations, and good agreement was obtained.