J. Gilgert

Some Insights into the Fatigue Crack Propagation in Tubes Under Internal Pressure — Proposition of Predicting Models

This study is a summary of works performed on fatigue crack propagation, that it is by carrying out experimental tests, or numerical simulations, or those using empirical models, relating principally to thick plates in three points bending, in tension and to thick tubes under internal pressure. The objective is to give the broadest possible comparison of various results allowing the follow-up of the shape evolution of semi-elliptic surface defect during its propagation in fatigue. This review work enabled us to conclude that the form variation of a semi-elliptic defect propagating by fatigue in a cylinder under internal pressure, can be obtained by tests on thick plate in tension, or by the use of model proposed by Mahmoud [36, 37] obtained on plate in tension, and model proposed by Boukharouba et al. [31] obtained and validated by the experimental results on tube under internal pressure.

Hydrogen Effect on Local Fracture Emanating from Notches in Pipeline Steels

The comparative assessment strength and fracture of three API grade pipeline steels: X52; X70 and X100 has been done for conditions of hydrogenating. The factors of cathodic hydrogen charging, time of exposition, hydrogen concentration in metal and applied load were taken into account. The relationship between hydrogen concentration and critical (failure) loading has been found. Also, the existence of some critical hydrogen concentration, which causes the significant loss of local fracture resistance of material, was shown.

Hydrogen Effect on Fatigue Life of a Pipe Steel

Transport by pipe is the means more used, at the pr esent time, to convey energies of their point of extraction until their field sites f inal. To limit any risk of explosion or of escape and thus to limit the geological problems of pollut ion and the human risks, it is necessary to be able to know the mechanical properties of the st e l used in the manufacture of these pipes. With the reduction in oil stocks, it is necessary t o find a new energy. Hydrogen is this new energy vector, it thus will also be necessary to be a l to transport it. This study makes it possible to emphasize the assignment of the lifespa n of hydrogen on a pipeline steel normally used in the transport of gas. The fatigue tests in 3 points bending are carried out on samples not standards because of dimensions of the tube of origin.