EXPERIMENTAL VALIDATION OF A FINITE-ELEMENT MODEL TO SIMULATE AN IMPACT ON PIPELINE DUE TO VEHICLES OR HEAVY OBJECT FALL

摘要

This paper deals in a first part with an experimental program aimed at studying mechanical impacts on pipelines. Tests have been performed at CRIGEN-ENGIE-LAB, the Center of Research and Innovation for Gas and New Energies of ENGIE (previously GDF SUEZ) on pipes under pressure and pipes without internal pressure with an impact tool whom length is greater than the external diameter of the pipes and a tool similar to an excavator tooth. In a first part, the paper presents the tests which show a very good behavior of the pipelines. None have failed for the large impact-tool, which is equivalent in terms of impact energy to a 1000 kg-vehicle impacting a pipeline at ~32 km.h~(-1) (~20 miles.h~(-1)). In a second part, the paper deals with existing analytical solutions: the Det Norske Veritas model for dent assessment and the EPRG model for mechanical damage assessment due to an excavator tooth. Comparisons with the CRIGEN tests show that the DNV equation is not always conservative in terms of predicted rupture energy and that the third-party damage EPRG model predicts correctly the rupture for the tooth-like tool but does not seem adapted for the longer tool. In a third part, an explicit finite-element model (performed with the commercial software Abaqus) has then been used to simulate numerically the tests. Different material behavior laws have been tested: a classical elastic-plastic law and a law with a time-dependence (Cowper-Symonds). The comparison between the final geometry of the impacted pipeline and the computational solution is quite satisfactory. A numerical strain criterion is extrapolated and then applied to some real configurations. This paper presents the tests, the analytical comparisons, the computational models and some applications to the fall of heavy long objects as well as vehicle impact on pipelines.