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

The effects of a single tensile overload on the stress, strain and displace ment fields for a three dimensional semi-circular extending crack have been studied using an elastic-plastic finite element model. The results show th at the application of a single tensile overload caused an immediate drop in the crack opening stress levels, but with further crack extension the open ing stress levels rapidly rose to values higher than those before the appli cation of the overload. It is found that the introduction of a single tensi le overload increases the local residual compressive stress ahead of the cr ack front and, with the growth of the crack, the magnitude of this local co mpressive stress decreases. The results also show that the introduction of a single tensile overload increases the crack opening displacement, and tha t with further crack extension the crack opening displacement decreases rap idly to a value less than that before the application of the overload. The predicted crack opening displacements from finite element analysis were com pared with those measured from direct in-situ SEM observations, and good ag reement was obtained. (C) 1999 Elsevier Science Ltd. All rights reserved.