Effect of lateral impact loads on failure of pressurized pip(10)

202CSNgandWQShen

Fig.6

Wf=Hversusl:(a)specimenssupportedbyasandfoundation;(b)specimenssupportedbyakaolinfoundation;and(c)specimenswithoutafoundation

support

AHP.Thereasonforthisinstabilityandanomalousphenomenonwaspossiblyduetotheexistenceoftheinternalpressure.Thisphenomenonhasnotbeenreportedfortheunpressurizedpipelines.Thecauseisstillunclear.Furtherexplorationintothisproblemisveryimportant,becausemostoftheprac-ticaloilandgaspipelinesintheindustrieshavehighinternalpressuresandareverylongfortransportingoilorgas,especiallywhenlyingontheseabed.

Theamountofenergyabsorbedbythefoundationwasestimatedanditwasfoundthatitwasverysmallwhencomparedwiththeinitialimpactenergy.Forexample,theenergiesabsorbedbythesandfoun-dationwere4.53,4.88,3.91,and7.08JinthetestsA3,ALP4,AMP2,andAHP5,respectively.

Figure7showsthecomparisonsofthevariationoffversuslforthepresentpipespecimensA,B,andCwithspecimensEinreference[3],specimensC12andC13inreference[6],andthosespecimenswith-outinternalpressureinreference[5].Thecommonfeaturesofallthespecimensaretheimpactlocation,e.g.mid-spanimpacts,andasimilarratioof2L/D,e.g.10forspecimensA,B,C,andEandthoseunpres-surizedpipespecimensand9.5and10.6forspeci-mensC12andC13.Moreover,nofractureoccurredforthespecimensshowninFig.7.ThedifferenceofratioD/Hforallthespecimenswassmall,e.g.35.6forspecimensA,B,C,C12,andC13;30forspecimenE;and35.3fortheunpressurizedspecimens.Allplotsexceptthosethatcorrespondingtothecurrentspeci-mensA,B,andCgatheredaroundastraightline.TherestraintatsupportwasdifferentforthecurrentspecimensA,B,andCfromtheremainingspecimensinFig.7.AlthoughafullyclampedsupportwasemployedforallspecimensinFig.7,themovementintheaxialdirectionforthepresentspecimensA,B,andCwasallowed.Thiswasthemainreasonforthesigni cantincreaseoffforspecimensA,

B,

Onewouldexpectthatthehigh-pressurizedspeci-menAHP5wouldhavealowerde ectionthanthelow-pressurizedspecimenALP2becauseofthelessimpactenergyandhigherinternalpressurerecordedinTable1.However,specimenALP2hadaWf1¼26.67mmwithanimpactenergyEk¼1022J,whereasAHP5hadaWf1¼31.88mmandEk¼984J.Thisindividualresultwasnottheonlyonethatshowedanobviousanomalousbehaviour.Therewasatendencyexistingbetweenthetwogroups,forexample,fromTable1,whereanaveragevalueofWf1¼31.64mmwithanaverageimpactenergyEk¼1086Jforthelowerpressurizedspeci-menALPcomparedwithWf1¼33.18mmandEk¼1035Jforthehigherpressurizedspecimen

Proc.IMechEVol.220PartE:J.ProcessMechanicalEngineering

Fig.7

Wf=Hversusl:(S,A,W),presentspecimensA,B,andC,respectively;(Â,4),specimensC12andC13[6];(Ã),unpressurizedpipespecimens[5];and(þ),specimenE[3]

JPME97#IMechE2006