Effect of lateral impact loads on failure of pressurized pip(2)

194CSNgandWQShen

reference[6].Atotalof226impacttestswereconductedonthedifferentgeometriesandinternalpressurelevelpipespecimens,whichwerefullyclampedatbothendsandimpactedtransverselybywedge-shapedindentersatdifferentpositions.

Athree-dimensionaldynamicnon-linear niteelementanalysis(FEA)waspresentedinreference[7]inordertosimulatetheactualdynamicinelasticresponseofallthepipesthatweresubjectedtoimpactloading,asreportedinreference[6].Agoodagreementwasobtainedbetweenthenumericalpre-dictionsandthecorrespondingexperimentalresultsforboththecriticalinitialimpactenergyandthemaximumpermanenttransversedisplacementswhenfailureoccurred.

Thetheoreticalanalysisinreference[4]hasbeenfurtherdevelopedtopredictthequasi-staticresponseandtheonsetoffailureforboththepress-urizedandunpressurizedpipelines[8].Themaxi-mumstrainfailurecriterion,theeffectofmaterialstrainratesensitivity,andanempiricalformulaforestimatingtheplastichingelengthwereusedintheanalysis.Goodagreementswereachievedbetweenthetheoreticalpredictionsandthecorrespondingexperimentalresultsinreference[6]forboththecriticalinitialimpactenergyandthemaximumpermanenttransversedeformationofthepipe.

Somefoundationspossiblysupportthepipelinesinthepracticalworkingenvironment,e.g.oil-trans-portationpipelineslyingonseabed.Theeffectof

thefoundationonthedynamicresponsesandfailureofpipelineswhensubjectedtoanaccidentimpactmaybesigni cantandhasnotbeeninvestigatedinthepreviouspublishedarticles.Therefore,aseriesofcarefullyinstrumentedtestsandnumericalsimu-lationsonpressurizedandunpressurizedpipessup-portedbydifferentfoundationswereconductedintheDepartmentofMechanicalandDesignEngineer-ingattheUniversityofPortsmouthforpredictingthefailureofpipelinesundersevereimpactloading.

22.1

EXPERIMENTALDETAILS

Testfacilitiesandinstrumentation

Aschematicdiagramoftheconnectionofinstru-mentsandequipmentsforcarryingouttheexper-imentalworkisshowninFig.1.Apairoftimesensorswas xedatthedrophammerrig,wheretheinitialvelocityoftheindenteratthetimeofimpactingonthetopsurfaceofthepipespecimencouldbepredictedandrecordedusingadigitaltimerandaspeciallydesignedelectroniccircuit.ThearrangementfortheunpressurizedtestisshowninFig.2(a).Steelplatessurroundingthepressurizedpipespecimenswereusedinthepress-urizedtest,asshowninFig.2(b),inordertostoppossibledebrisbeingprojectedduringtheimpact

test.

Fig.1Aschematicdiagramshowingtheconnectionofthetestinstrumentsandequipments

JPME97#IMechE2006

Proc.IMechEVol.220PartE:J.ProcessMechanicalEngineering