Abdelwaheb Amrouche

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.

J Integral Computation for Cracks in Polypropylene Pipes under Internal Pressure

In the present work, the three-dimensional finite element method is used to analyze the propagation criteria for a semi-elliptical crack in a polypropylene pipe under internal pressure. The crack propagation behavior is analyzed by J-integral calculation. The effects of the crack position in the pipe and the loading, as well as the size and configuration of the crack, are examined. The results obtained enable us to deduce that the propagation of a crack depends on several factors.

Study of Fretting Fatigue Crack Initiation For Riveted Al 6xxx Components

Riveting is a procedure widely used for fitting together two or more elements of a structure, that could be of the same or different material. In these assemblies the stress field is complex and a number of parameters, including effect of the geometrical discontinuities, contact between elements, tightening, material properties and applied load must be considered. The current work focuses on the study of fretting fatigue crack formation in common 6XXX aluminum alloys, used in land transportation equipments, and the determination of the characteristic crack initiation sites by means of both experimental and numerical methods. 3D finite element models were validated by the experimental results obtained with strain gauges. The influence of the contact friction coefficient at the fretting surface and fastening forces on the initiation of cracks, are discussed by the comparison of the different numerical results.