Studies On The Dynamic Response And The Perforation Failure Of The Water-filled Pre-pressurized Pipeline Impacted Laterally By Missile

Pipelines under high pressure are widely used in the nuclear, gas and petroleum industries to convey gases and liquids over long distance. These pipes are often subjected to impact damage that results in mass devastation. It is usually not the initial explosion but the secondary damage to pipelines and container system by flying missiles that results in the escape of flammable or even explosive fluids that leads to disastrous results. So the importance of studying the dynamic response and failure of circular pipes under local impact loads, which can provide the safety calculations and designs, are obvious. Many researchers studied the response of the empty pipes under the local static and impact loads and have achieved some results, which can be used in the design of pipelines. However, only a few scholars studied the effect of the media and pressure filled in the pipelines, although most of the tubes were working under pressure and with filled media. In the previous literatures there are some conflicting conclusion for the presence of essentially incompressible contents. The influence of internal pressure is also different in different tests. So more experimental data and theoretical analyses are needed to provide a clear physical picture of perforation failure.In our research two groups of tests were carried out and 185 specimens of three-span continuous pipe beam were used in a series of tests. Three kinds of indenter nose shapes were used: blunt-nose, hemisphere-nose and 90?conical-nose. In the experiments the time histories of impact forces and those of pressure changes were recorded and the different failure modes of dishing, plugging and petalling were found in the tests. The results of the experiments showed that the ballistic perforation energy would decrease when the pipelines were filled by media. When the pipe was filled water and not pressurized, the perforation energy was 20-30% less than that of empty ones in the case of thin pipes and 2-3% less for thick pipes. It also decreases when the internal pressure increases. To penetrate the tube, the highest perforation energy was needed by the hemispherical missile, less energy by the conical missile and the least energy by the blunt missile under the same condition. It shows that the tube wall is most likely to be penetrated by the blunt missile. When the missile impacts the tube the internal pressure will increase and the dishing deformation of the tube wall was the main reason for the increase of internal pressure.The computer code LS-DYNA was used to simulate the whole perforation process of the pipeline impacted by missiles. The mechanism of coupling interaction between a (slave) Lagrangian geometric entity and a (master) ALE or Eulerian geometric entity was used to simulate the coupling interaction between the response of water filled in the tube and the response of the tube wall. The computer active movie showed that the perforation process included three steps: Firstly, the missile nose contacted the pipe wall and the force increasedquickly. (This step is very short.) Secondly, the contact region enlarged and the pipe wall started deforming dishingly and this process was a little longer. Finally, the perforation occurred. The simulation results show that the ballistic velocity decreases with the increase of the internal medium's density. The ballistic velocity also decreases with the increase of the missile's mass and the correlation between the ballistic velocity and missile mass is a linear decrease in the logarithm coordinate. The simulation results match fairly well with the test values and analytical results.On the basis of the experimental and computer simulation results we have improved the model of the beam-on-foundation by introducing the concept of added-mass and added-damping to analyze the perforation of the pipelines pre-pressurized by water. The effect of the internal pressure was reflected by added foundation reaction or membrane factor. The results show that the improved mode can reflect the effect of the water and pressu...