The study of the nocivity of a plain dent on the burst pressure of a pipeline is presented in this paper. According to our results, it seems that the empirical rule of tolerance of a dent with a depth less than 10% of the pipe diameter is very conservative. It is then preferable to use a failure criterion based on ductility. In this study, we have not chosen a local strain energy criterion because the coefficients are very difficult to identify. The authors have used Oyane's criterion which is a local strain criterion. The increase of fracture resistance due to strain hardening during dent formation has been taken into account. The microhardness measurements at the base and outside the dent show the effect of hardening in the dented zone: it increases ultimate strength by strain hardening to about 30%. Finite element method computation confirms that the critical value of the Oyane's criterion is not reached due to the stress relaxation phenomenon under internal pressure effect. This phenomenon eventually coupled with pipe thickness heterogeneity can explain why failure does not occur at dent location but outside. One can say that a A37 steel dented vessel has the same burst pressure than a vessel without defect. Consequently, it is not necessary to repair or to change a dented pipe.
Study of the influence of dent depth on the critical pressure of pipeline
Untersuchung des Einflusses der Einbeulungstiefe auf den kritischen Druck einer Pipeline
Engineering Failure Analysis ; 21 ; 40-51
2012
12 Seiten, 13 Bilder, 8 Tabellen, 19 Quellen
Article (Journal)
English
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