Cold expansion effect on the initiation and the propagation of the fatigue crack

In this study, an experimental and numerical investigation was carried out to quantify the effect of the cold expansion on the initiation and the propagation of the fatigue crack. The fatigue life improvement of the damaged structures after the cold expansion process was investigated with the single edge pre-cracked specimens of aluminium alloy which are used in land transport components. Three radii and three degrees of cold expansion were performed at the crack tip. The number of cycles to obtain a new crack initiation (life time), are analysed from the different cases. A numerical investigation with a numerical code (FEM ANSYS code) is conducted to determine the residual stress field and the size of the plastic zone generated by the cold expansion and to establish the influence of the degree of cold expansion (DCE) on the different parameters. Three radii and six degrees of cold expansion were performed in this numerical investigation. It has been shown that the DCE has an influence on the size of the zone of compressive residual stresses (ZCRS) and on the size of the zone of plastic deformation (ZPD), but it appears that the DCE has no influence on the level of the maximum residual stresses in our case. (C) 2003 Elsevier Ltd. All rights reserved.