ABSTRACT REFERENCE NUMBER: ICF100277PR EFFECT OF NOTCH SHARPNESS AND COLD EXPANSION ON THE FATIGUE CRACK ARREST

A fatigue crack can be stopped by a decrease of the notch sharpness and by residual compressive stresses at the crack tip [1]. The decrease of the notch sharpness is generated by a drilling at the crack tip and the residual compressive stresses by a cold expansion. This work is about two aluminium alloys which are used in land transport components. Three drilling radius and five expansion rate were performed at the crack tip. The required number of cycles to obtain a new crack initiation, the crack propagation rate and the crack tip opening displacement are studied and analysed from the different cases. The necessary number of cycles to obtain a new crack initiation is called Time Life. The curves time life versus the applied stress are similar to the Wöhler curve and the same use can be done. The residual compressive stresses and the plastic zone size are determined from a numerical calculation code. Without any cold expansion the fatigue life is controlled by the local stress concentration factor. In this case the fatigue life can be explained from a power law of the hole radius[2]. The crack propagation rate is minimum at the crack initiation and is depending on the hole radiu