2012 Vol. 32, No. 4
Display Method:
2012, 32(4): 337-345.
doi: 10.11883/1001-1455(2012)04-0337-09
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Abstract:
Inordertoinvestigatetheanti-penetrationmechanismandtherelationshipbetweendynamic behaviorandanti-perforationperformanceoffiberreinforcedpolymercomposites(FRP),theexperimentwhichspherefragmentsimulatedprojectilespenetratecompositelaminateswasconductedto characterizetheanti-perforationabsorbingenergyproperty.Thecharacteristicofinstantaneousdeformationandfailurewasanalyzedbyhighspeedphotography, andtheanti-penetratingenergydissipationmodelofcompositelaminateswasinvestigatedbyCTandSEMscanningtechniquesandother methods.Theresultsshowthattheanti-perforationabsorbedenergyoflaminatesunderhighvelocity impactisproportionaltoimpactvelocity,theprocessofpenetratinglaminatesunderhighvelocityisa courseofdynamicdeformationunderhighstrainrateforcomposite,andthatdynamicmechanicalbehaviorunderhighstrainratehasaremarkableinfluenceontheanti- perforationabsorbedenergyof laminates.Atthesametime,thepropagatingcharacteristicofshockwavesinFRPdeterminedthe partitionofdifferentphaseoffailuremodel,anddeterminedthefailurezoneoflaminates.Basedon dynamicsinstantaneousanalysisofpenetratingprocessathighvelocity,thetwo-stagedynamicfailure modelofanti-perforatingabsorbedenergywasestablished,andthemodelagreedwellwiththeexperimentalresults. Itindicatedthatthestrainrateeffectandtheinertiaeffectshouldnotbeignoredinthe researchofantiimpactperformanceofFRP.
Inordertoinvestigatetheanti-penetrationmechanismandtherelationshipbetweendynamic behaviorandanti-perforationperformanceoffiberreinforcedpolymercomposites(FRP),theexperimentwhichspherefragmentsimulatedprojectilespenetratecompositelaminateswasconductedto characterizetheanti-perforationabsorbingenergyproperty.Thecharacteristicofinstantaneousdeformationandfailurewasanalyzedbyhighspeedphotography, andtheanti-penetratingenergydissipationmodelofcompositelaminateswasinvestigatedbyCTandSEMscanningtechniquesandother methods.Theresultsshowthattheanti-perforationabsorbedenergyoflaminatesunderhighvelocity impactisproportionaltoimpactvelocity,theprocessofpenetratinglaminatesunderhighvelocityisa courseofdynamicdeformationunderhighstrainrateforcomposite,andthatdynamicmechanicalbehaviorunderhighstrainratehasaremarkableinfluenceontheanti- perforationabsorbedenergyof laminates.Atthesametime,thepropagatingcharacteristicofshockwavesinFRPdeterminedthe partitionofdifferentphaseoffailuremodel,anddeterminedthefailurezoneoflaminates.Basedon dynamicsinstantaneousanalysisofpenetratingprocessathighvelocity,thetwo-stagedynamicfailure modelofanti-perforatingabsorbedenergywasestablished,andthemodelagreedwellwiththeexperimentalresults. Itindicatedthatthestrainrateeffectandtheinertiaeffectshouldnotbeignoredinthe researchofantiimpactperformanceofFRP.
2012, 32(4): 346-354.
doi: 10.11883/1001-1455(2012)04-0346-09
Abstract:
Forinvestigatingthe mechanicalbehaviorandself-sharpeningoftungsten-fiber/metallic glass-matrixcompositematerial,quasi-statisticanddynamictestsaswellaspenetrationexperiments ofcompositematerialpenetratorsintosteeltargetsareconducted.Thenthefailuremodesofcompositematerialwereidentifiedsystemicallybasedonmetallographicanalysisandcomparedwiththeresultsofquasi staticanddynamictests.Finally,themechanismofself-sharpeningbehaviorofmaterial wasdiscussed.Thequasi-statisticanddynamicbehaviorsandtheself-sharpeningphenomenaofmaterialwereobtained. Itisfoundthatthematerialhasnotablestrainrateeffect,moreover,themainfailuremodesofthecompositematerialinthepenetrationprocessislocalizedshearfailureandfracture. Therearefourshearfailuremodesforthecompositematerialandthreefailuremodesforthetungsten fiber.
Forinvestigatingthe mechanicalbehaviorandself-sharpeningoftungsten-fiber/metallic glass-matrixcompositematerial,quasi-statisticanddynamictestsaswellaspenetrationexperiments ofcompositematerialpenetratorsintosteeltargetsareconducted.Thenthefailuremodesofcompositematerialwereidentifiedsystemicallybasedonmetallographicanalysisandcomparedwiththeresultsofquasi staticanddynamictests.Finally,themechanismofself-sharpeningbehaviorofmaterial wasdiscussed.Thequasi-statisticanddynamicbehaviorsandtheself-sharpeningphenomenaofmaterialwereobtained. Itisfoundthatthematerialhasnotablestrainrateeffect,moreover,themainfailuremodesofthecompositematerialinthepenetrationprocessislocalizedshearfailureandfracture. Therearefourshearfailuremodesforthecompositematerialandthreefailuremodesforthetungsten fiber.
2012, 32(4): 355-361.
doi: 10.11883/1001-1455(2012)04-0355-07
Abstract:
Liquidjetsformedwhenbubblescausedbyunderwaterexplosioncollapsecouldseriously threatenthelocalstrengthofwarships.Inordertostudythedamageeffectofvesselstructuresubjectedtobubblejet, aseriesofunderwaterexplosiontrialswereperformedbyusingatypicalcabinmodel. Waterpressure,bubblepulsatingcycle,thedynamicstrainandplasticdeformationofoutplates wereobtained.Dynamicalresponsesofcabinstructurewithvariousimpulsivefactorswereanalyzed, waterpressurewasmeasured,theoccurrenceofbubblejetwasthendiscussed.Damageeffectandinfluencerangeofoutplatescausedbybubblejetwereinvestigated. Theresultsshowedthatcompared withshockwaveload,thejetimpactcouldconcentratebubbleenergyandcauseseriousdamagetolocalstructureofwarships. Undercertaincircumstance,thedamageeffectcausedbybubblejetwould bemoreseriousthanthatcausedbyshockwaveloading.Therefore,intheresearchonproximityunderwaterexplosion, inadditiontotheshockwaveloading,thebubbleloadingcouldnotbeneglected.
Liquidjetsformedwhenbubblescausedbyunderwaterexplosioncollapsecouldseriously threatenthelocalstrengthofwarships.Inordertostudythedamageeffectofvesselstructuresubjectedtobubblejet, aseriesofunderwaterexplosiontrialswereperformedbyusingatypicalcabinmodel. Waterpressure,bubblepulsatingcycle,thedynamicstrainandplasticdeformationofoutplates wereobtained.Dynamicalresponsesofcabinstructurewithvariousimpulsivefactorswereanalyzed, waterpressurewasmeasured,theoccurrenceofbubblejetwasthendiscussed.Damageeffectandinfluencerangeofoutplatescausedbybubblejetwereinvestigated. Theresultsshowedthatcompared withshockwaveload,thejetimpactcouldconcentratebubbleenergyandcauseseriousdamagetolocalstructureofwarships. Undercertaincircumstance,thedamageeffectcausedbybubblejetwould bemoreseriousthanthatcausedbyshockwaveloading.Therefore,intheresearchonproximityunderwaterexplosion, inadditiontotheshockwaveloading,thebubbleloadingcouldnotbeneglected.
2012, 32(4): 362-367.
doi: 10.11883/1001-1455(2012)04-0362-06
Abstract:
Thispaperstudiesthedynamicbucklingproblemoftheflexibleelectroniccomponents,a stifffilmboundtoacompliantsubstrate.ThesubstrateandthefilmaredescribedbythesmalldeformationtheoryandtheKirchhoffplaneplatetheory, respectively.ALagrangefunctionofthefilm isobtained,includingitsstrainenergy,kineticenergyandtheworkfromthesubstrate.Dynamic bucklinggoverningequationofthefilmisdeducedaccordingtotheEuler-Lagrangeequation.Thedynamicresponsesofthefilmunderlinearloadaresolved. Andthecriticalloadisdeterminedbythe B-Rcriterion.Thecriticalloadindynamicbucklingislargerthanthatinstaticbuckling.Theamplituderesponseindynamicbucklingvibratesaroundthatinstaticbuckling.
Thispaperstudiesthedynamicbucklingproblemoftheflexibleelectroniccomponents,a stifffilmboundtoacompliantsubstrate.ThesubstrateandthefilmaredescribedbythesmalldeformationtheoryandtheKirchhoffplaneplatetheory, respectively.ALagrangefunctionofthefilm isobtained,includingitsstrainenergy,kineticenergyandtheworkfromthesubstrate.Dynamic bucklinggoverningequationofthefilmisdeducedaccordingtotheEuler-Lagrangeequation.Thedynamicresponsesofthefilmunderlinearloadaresolved. Andthecriticalloadisdeterminedbythe B-Rcriterion.Thecriticalloadindynamicbucklingislargerthanthatinstaticbuckling.Theamplituderesponseindynamicbucklingvibratesaroundthatinstaticbuckling.
2012, 32(4): 368-373.
doi: 10.11883/1001-1455(2012)04-0368-08
Abstract:
Toexplorethedeformationmodesofwarshipstructuressubjectedtoclose-rangeexplosionofwarheadandfurnishexperimentaldata,thedeformationanddamagemodesofclampedlargescalesquareplatesunderclose-rangeblastloadingwereanalyzedthroughmodelexperiments.Onthebasisoftheanalysis,thefailurestrainofQ235steelwasobtainedutilizingbiaxialstrainhypothesisandbulkequivalenttheoryviameasuringthethinningrateofcrackedpetals.Basedontheexperimentalresults,arupturecriterionofstructuressubjectedtolocalisedblastloadingwaspresentedafteremployingrigid-plasticassumptionandenergydensityrule.Moreover,predictionsforexperimentsweremade.Theresultsshowthattheclampedplatesexhibitthreedifferentdeformationanddamagemodeswiththeincreasingoftheloadintensity.Thepredictionsbymakinguseoftherupturecriterionfortestconditionscorrelatewellwiththeexperimentalresults.
Toexplorethedeformationmodesofwarshipstructuressubjectedtoclose-rangeexplosionofwarheadandfurnishexperimentaldata,thedeformationanddamagemodesofclampedlargescalesquareplatesunderclose-rangeblastloadingwereanalyzedthroughmodelexperiments.Onthebasisoftheanalysis,thefailurestrainofQ235steelwasobtainedutilizingbiaxialstrainhypothesisandbulkequivalenttheoryviameasuringthethinningrateofcrackedpetals.Basedontheexperimentalresults,arupturecriterionofstructuressubjectedtolocalisedblastloadingwaspresentedafteremployingrigid-plasticassumptionandenergydensityrule.Moreover,predictionsforexperimentsweremade.Theresultsshowthattheclampedplatesexhibitthreedifferentdeformationanddamagemodeswiththeincreasingoftheloadintensity.Thepredictionsbymakinguseoftherupturecriterionfortestconditionscorrelatewellwiththeexperimentalresults.
2012, 32(4): 376-383.
doi: 10.11883/1001-1455(2012)04-0376-08
Abstract:
Theprocessofrubbercompositearmorantishapedchargejetpenetratedwasdividedfour partsbasedonthejetdeformationwhentheshapedchargejetpenetratedtherubbercompositearmor. Theresultswereacquiredthattheinterferencespeedinterval,interferencefrequencyandsurpluspenetrationabilityoftheshapedchargejetwiththerubbercompositearmorbasedonthestresswaveand Kelvin-Helmholzinstabilitytheory.Theeffectsoftherubberlayerthicknessanddipangleofthearmorforthecompositearmorantijetpenetratedwerestudiedbytheoreticalandexperi entalstudy. Theresultsshowedthatwhenthedipangleat60andtherubberlayerthicknessattherangefrom 3mmto3.5mmtherubbercompositearmorhasthebestprotectionability.
Theprocessofrubbercompositearmorantishapedchargejetpenetratedwasdividedfour partsbasedonthejetdeformationwhentheshapedchargejetpenetratedtherubbercompositearmor. Theresultswereacquiredthattheinterferencespeedinterval,interferencefrequencyandsurpluspenetrationabilityoftheshapedchargejetwiththerubbercompositearmorbasedonthestresswaveand Kelvin-Helmholzinstabilitytheory.Theeffectsoftherubberlayerthicknessanddipangleofthearmorforthecompositearmorantijetpenetratedwerestudiedbytheoreticalandexperi entalstudy. Theresultsshowedthatwhenthedipangleat60andtherubberlayerthicknessattherangefrom 3mmto3.5mmtherubbercompositearmorhasthebestprotectionability.
2012, 32(4): 384-392.
doi: 10.11883/1001-1455(2012)04-0384-09
Abstract:
Anadaptiveaxisymmetricfiniteelementmethod(FEM)-smoothedparticlehydrodynamics (SPH)couplingalgorithmisproposedtoaccuratelyandefficientlysimulatehighvelocityimpactproblems. ItusesFEMtocalculateatthebeginning.Duringthedeformationprocess,itautomatically convertsdistortedelementstoparticlesandusesSPHforcalculationattheseregionswheredistorted elementsappear.Intheadaptivecouplingalgorithm,anewcouplingalgorithmisappliedtolinkelementsandparticlesaccurately, andaminimuminterioranglecriterioncombinedwithagroup-based conversionmannerisadoptedtoconvertelementstoparticles.Severaltypicalhighvelocityimpact problemsarecalculated.Firstly,thestresswavepropagationiscalculatedtotesttheaccuracyofthe newelement-particlecouplingalgorithm.Then,theTaylortestiscalculatedtovalidatetheadaptive couplingalgorithmandthecorrespondingcode.Finally,thesimulationofprojectilespenetratingaluminumandconcreteplatesispresented. Theresultsshowthattheadaptivecouplingalgorithmisaccurateandefficientanditisverysuitableforthesimulationofhighvelocityimpact.
Anadaptiveaxisymmetricfiniteelementmethod(FEM)-smoothedparticlehydrodynamics (SPH)couplingalgorithmisproposedtoaccuratelyandefficientlysimulatehighvelocityimpactproblems. ItusesFEMtocalculateatthebeginning.Duringthedeformationprocess,itautomatically convertsdistortedelementstoparticlesandusesSPHforcalculationattheseregionswheredistorted elementsappear.Intheadaptivecouplingalgorithm,anewcouplingalgorithmisappliedtolinkelementsandparticlesaccurately, andaminimuminterioranglecriterioncombinedwithagroup-based conversionmannerisadoptedtoconvertelementstoparticles.Severaltypicalhighvelocityimpact problemsarecalculated.Firstly,thestresswavepropagationiscalculatedtotesttheaccuracyofthe newelement-particlecouplingalgorithm.Then,theTaylortestiscalculatedtovalidatetheadaptive couplingalgorithmandthecorrespondingcode.Finally,thesimulationofprojectilespenetratingaluminumandconcreteplatesispresented. Theresultsshowthattheadaptivecouplingalgorithmisaccurateandefficientanditisverysuitableforthesimulationofhighvelocityimpact.
2012, 32(4): 393-398.
doi: 10.11883/1001-1455(2012)04-0393-06
Abstract:
Thedensityuniformityandthecorrespondingsizeeffectwereanalyzedfortwodifferent foamaluminum materials.Analyzedresultsshowthatthemorenon-uniformthedensitydistribution ofthefoamaluminum,themoresignificantthesizeeffect.Butifthedensitydistributionintervalis smallerandinlinewithnormaldistribution,thesizeeffectisweaker.Basedontheassumptionofthe stressuniformityinthesplitHopkinsonpressurebartests,thequartzpieceswereusedtomeasurethe timerequiredbythestressuniformityprocessatthetwoendsofthespecimens.Itisfoundthatthe largertheaxialsizeofthefoamspecimen,themoreevidenttheinfluenceoftheinertialeffect.And therightaxialsizeswerechosentodecoupletheinertialeffectofthespecimen(waveeffect)fromthe strainrateeffect.Theexperimentalresultsdisplaythatthefoam materialshaveobviousstrainrate effects.
Thedensityuniformityandthecorrespondingsizeeffectwereanalyzedfortwodifferent foamaluminum materials.Analyzedresultsshowthatthemorenon-uniformthedensitydistribution ofthefoamaluminum,themoresignificantthesizeeffect.Butifthedensitydistributionintervalis smallerandinlinewithnormaldistribution,thesizeeffectisweaker.Basedontheassumptionofthe stressuniformityinthesplitHopkinsonpressurebartests,thequartzpieceswereusedtomeasurethe timerequiredbythestressuniformityprocessatthetwoendsofthespecimens.Itisfoundthatthe largertheaxialsizeofthefoamspecimen,themoreevidenttheinfluenceoftheinertialeffect.And therightaxialsizeswerechosentodecoupletheinertialeffectofthespecimen(waveeffect)fromthe strainrateeffect.Theexperimentalresultsdisplaythatthefoam materialshaveobviousstrainrate effects.
2012, 32(4): 399-403.
doi: 10.11883/1001-1455(2012)04-0399-05
Abstract:
ThemesodeformationofthealuminumfoamspecimensimpactedbySHPBwassynchronouslycapturedbyusingahigh- speedcamera.Andthestraindistributionandfailuremodesofthe specimenswereanalyzed.Theinvestigationshowsthatthestraindistributioninthealuminumfoam specimensisnotuniform,thestrainsandstrainratesnearthetwoendsofthespecimensaremuch greaterthanthoseinthemiddleportionofthespecimens,whichmeansthattheassumptionofuniformdeformationofspecimensinSHPBtestcannotbestrictlysatisfiedforaluminumfoam. Therefore, somemodificationindataprocessingshouldbedoneintheSHPBtestsonaluminumfoam.
ThemesodeformationofthealuminumfoamspecimensimpactedbySHPBwassynchronouslycapturedbyusingahigh- speedcamera.Andthestraindistributionandfailuremodesofthe specimenswereanalyzed.Theinvestigationshowsthatthestraindistributioninthealuminumfoam specimensisnotuniform,thestrainsandstrainratesnearthetwoendsofthespecimensaremuch greaterthanthoseinthemiddleportionofthespecimens,whichmeansthattheassumptionofuniformdeformationofspecimensinSHPBtestcannotbestrictlysatisfiedforaluminumfoam. Therefore, somemodificationindataprocessingshouldbedoneintheSHPBtestsonaluminumfoam.
2012, 32(4): 404-410.
doi: 10.11883/1001-1455(2012)04-0404-07
Abstract:
DynamicfiniteelementsoftwareANSYS/LS-DYNA wasusedtosetupthefinefiniteelementmodelforKiewitt8single- layerreticulatedshellwithaspanof40msubjectedtoblastloading locatedatcentralpoint.Theselectionanddeterminationofmaterialparametersandconstitutivemodels, elementtypes,meshdimensionandgenerationandtheapplicationofsymmetricstructurewere furthervalidatedtoguaranteetheprecisionandfeasibilityofdynamicanalysisforfiniteelementanalysis. Theresponserulesofthestructureunderblastloadingwithdifferentrise-spanrates,standoff distancesandthicknessesofroofboardingwereobtainedthroughthecomparisonoftheplasticstrain, theplasticdevelopmentdegreeanddisplacementofmembers.Inaddition,theeffectofdifferentopeningrates, openingnumbers,openingdistributionsandopeningpositionsonroofboardingontheresponseofstructurewerealsostudiedbasedontheexplosionreliefofroofboa ding.Theresponseresultsoflong- spansingle-layerreticulatedshellstructureundercentralblastloadingweresummarized andtheoptimallayoutschemeofopeningsonroofboardingwasputforward,whichoffersthetheoreticalbasisforreasonabledefensedesignofreticulatedshellstructureforresistingblast.
DynamicfiniteelementsoftwareANSYS/LS-DYNA wasusedtosetupthefinefiniteelementmodelforKiewitt8single- layerreticulatedshellwithaspanof40msubjectedtoblastloading locatedatcentralpoint.Theselectionanddeterminationofmaterialparametersandconstitutivemodels, elementtypes,meshdimensionandgenerationandtheapplicationofsymmetricstructurewere furthervalidatedtoguaranteetheprecisionandfeasibilityofdynamicanalysisforfiniteelementanalysis. Theresponserulesofthestructureunderblastloadingwithdifferentrise-spanrates,standoff distancesandthicknessesofroofboardingwereobtainedthroughthecomparisonoftheplasticstrain, theplasticdevelopmentdegreeanddisplacementofmembers.Inaddition,theeffectofdifferentopeningrates, openingnumbers,openingdistributionsandopeningpositionsonroofboardingontheresponseofstructurewerealsostudiedbasedontheexplosionreliefofroofboa ding.Theresponseresultsoflong- spansingle-layerreticulatedshellstructureundercentralblastloadingweresummarized andtheoptimallayoutschemeofopeningsonroofboardingwasputforward,whichoffersthetheoreticalbasisforreasonabledefensedesignofreticulatedshellstructureforresistingblast.
2012, 32(4): 411-417.
doi: 10.11883/1001-1455(2012)04-0411-07
Abstract:
Aseriesofsingle-shotdetonationexperimentswereperformedtounderstandthematching characteristicsofwaveandflameinDDTforH2/airmixuresina60mmsquaretubethatwas2min length.Theion-probesandpressuretransducerswererespectivelyutilizedtogetthesignalofflame andwave,andhigh-speeddigitalimagingwasusedtotrackflamepropagationofDDTarea.The matchingruleofshock-flamewasachievedbyanalyzingtheintensity、velocityandpositioncharacteristicsofwaveandflameindifferenttimealongthetube. Theresultsindicatethatintensityofwaveand flameispositivefeedbackcharacteristicandthevelocityof waveandflameisalternantchange process.Thespeedamplitudeofflameisrapidthanthatofwaveindeflagrationphase.Thisresultin theoverdriverndetonationwaveformandflameistemporarilyinfrontofflamewhenflamecatchup wave.Shockisinfrontofflameinphasewhichtheoverdriverndetonationevolveintosteadydetonationwave
Aseriesofsingle-shotdetonationexperimentswereperformedtounderstandthematching characteristicsofwaveandflameinDDTforH2/airmixuresina60mmsquaretubethatwas2min length.Theion-probesandpressuretransducerswererespectivelyutilizedtogetthesignalofflame andwave,andhigh-speeddigitalimagingwasusedtotrackflamepropagationofDDTarea.The matchingruleofshock-flamewasachievedbyanalyzingtheintensity、velocityandpositioncharacteristicsofwaveandflameindifferenttimealongthetube. Theresultsindicatethatintensityofwaveand flameispositivefeedbackcharacteristicandthevelocityof waveandflameisalternantchange process.Thespeedamplitudeofflameisrapidthanthatofwaveindeflagrationphase.Thisresultin theoverdriverndetonationwaveformandflameistemporarilyinfrontofflamewhenflamecatchup wave.Shockisinfrontofflameinphasewhichtheoverdriverndetonationevolveintosteadydetonationwave
2012, 32(4): 418-422.
doi: 10.11883/1001-1455(2012)04-0418-05
Abstract:
Basedonnumericalsimulation,thedynamicresponseofhumanchestencounteringshockin freeblastfieldisinvestigated.CTImagesaretreatedusingthesoftwareofMimics,andthe3-Dmodelofhumanchestisestablished. Accordingtothecharacteristicsofeachbiologictissueinhuman chest,themodelandparametersofthematerialisrightlyselected.Usingfluid-structurecouplingfiniteelementsolverofLS- DYNAsoftware,thedynamicresponseofthelungsunderablastwaveis calculatedandanalyzed.Bythecalculatedpeakoverpressureandpositivephasedurationofincident shockwave,betweenDcandD1injurylevelofthelungsisevaluatedreferringtoBowenscurve.Observingchangesofpressureinsidethelungs, thestressvariationonthelungsurfaceandthemostseverelydamagedareaareobtained. Theshearstressisanalyzed,andpossibilityofdamagecausedby shearstressisunderstood.
Basedonnumericalsimulation,thedynamicresponseofhumanchestencounteringshockin freeblastfieldisinvestigated.CTImagesaretreatedusingthesoftwareofMimics,andthe3-Dmodelofhumanchestisestablished. Accordingtothecharacteristicsofeachbiologictissueinhuman chest,themodelandparametersofthematerialisrightlyselected.Usingfluid-structurecouplingfiniteelementsolverofLS- DYNAsoftware,thedynamicresponseofthelungsunderablastwaveis calculatedandanalyzed.Bythecalculatedpeakoverpressureandpositivephasedurationofincident shockwave,betweenDcandD1injurylevelofthelungsisevaluatedreferringtoBowenscurve.Observingchangesofpressureinsidethelungs, thestressvariationonthelungsurfaceandthemostseverelydamagedareaareobtained. Theshearstressisanalyzed,andpossibilityofdamagecausedby shearstressisunderstood.
2012, 32(4): 423-431.
doi: 10.11883/1001-1455(2012)04-0423-09
Abstract:
Dynamicmechanicalpropertiesofwater-saturatedrockunderuniaxialloadarehighlydifferentfromitsstaticmechanicalproperties, thereasonsofwhichcannotbeexplainedwellbasedon macro-mechanics.Accordingtomeso-mechanismofrockcompletestress-straincurveunderuniaxial compression,crackpropagationofwater-saturatedrockinfluencedbyporewaterunderdynamicload isanalyzedaswellasunderstaticload.Wheninitialfracturesaresubjectedtostaticuniaxialcompressionload, itcancausefreewatertoappearporewaterpressure,whichcanpromotetheexpansionof wingedcrackduetoitsextrudingwingedcrackoutwards.Intheconditionofdynamicuniaxialcompressionloads, freewaterappearcohesiveforcetohinderthepropagationofwingedcrack.Basedon compressivewingcrackpropagationmechanism,calculationformulasofstaticcompressivestrength anddynamiccompressivestrengthwithwaterunderuniaxialloadareobtained.Withthesamefracturetoughness, staticcompressivestrengthofwater-saturatedrockisevenlowerthanthatofdry rock.Bothofthemarelowerthandynamiccompressivestrengthofwater-saturatedrock.Staticand impactcompressiveexperimentsonair-driedandwater-saturatedsandstoneareconducted,theexperimentresultsareinagreementwiththeonesfromtheoreticalmodels.
Dynamicmechanicalpropertiesofwater-saturatedrockunderuniaxialloadarehighlydifferentfromitsstaticmechanicalproperties, thereasonsofwhichcannotbeexplainedwellbasedon macro-mechanics.Accordingtomeso-mechanismofrockcompletestress-straincurveunderuniaxial compression,crackpropagationofwater-saturatedrockinfluencedbyporewaterunderdynamicload isanalyzedaswellasunderstaticload.Wheninitialfracturesaresubjectedtostaticuniaxialcompressionload, itcancausefreewatertoappearporewaterpressure,whichcanpromotetheexpansionof wingedcrackduetoitsextrudingwingedcrackoutwards.Intheconditionofdynamicuniaxialcompressionloads, freewaterappearcohesiveforcetohinderthepropagationofwingedcrack.Basedon compressivewingcrackpropagationmechanism,calculationformulasofstaticcompressivestrength anddynamiccompressivestrengthwithwaterunderuniaxialloadareobtained.Withthesamefracturetoughness, staticcompressivestrengthofwater-saturatedrockisevenlowerthanthatofdry rock.Bothofthemarelowerthandynamiccompressivestrengthofwater-saturatedrock.Staticand impactcompressiveexperimentsonair-driedandwater-saturatedsandstoneareconducted,theexperimentresultsareinagreementwiththeonesfromtheoreticalmodels.
2012, 32(4): 432-438.
doi: 10.11883/1001-1455(2012)04-0432-07
Abstract:
Inordertopreventandcontrolindustrialdustexplosionandimprovetheaccuracyofdust explosiontests,anexperimentalresearchwascarriedouttohaveaninsightintotheexplosionbehaviorofhigh- andlow-volatiledustsinducedbydifferentignitionenergiesbyusingaSiwek20Lsphericalexplosiontestsystem. Ignitionenergyeffectondustexplosionbrisance(max.explosionpressure, max.pressurerisingrateandcombustionduration)andsensitivity (lowerexplosionlimit)andthe variationofexplosionsuppressioneffectivenessofinertsubstancealongwiththeignitionenergywere explored.Resultsshowthathigherignitionenergyimprovestheexplosionenergyreleaseandcombustionrateofdustcloud; theeffectofignitionenergyonexplosionbehaviorismoresignificantforless volatiledust.Incompletedeflagrationoflow-volatiledustundertheconditionoflowignitionenergy resultsintheadverseeffectofexplosion.Theadverseeffectofexplosionbecomesinconspicuousas thedustconcentrationincreases.Thelowerexplosionlimitdecreasessharplywiththeriseofignition energyforlow-volatiledust,whilethelowerexplosionlimitofhigh-volatiledustisnotsosensitiveto ignitionenergy.Moreover,explosionsuppressioneffectivenessofinertsubstancedecreaseswiththe riseofignitionenergy.Theignitionenergyof5~10kJisthemostappropriateforunderstandingthe lowerexplosionlimitoflow-volatiledustandtheexplosionsuppressioneffectivenessofinertsubstance. Theaboveresultsmaybevaluableforunderstandingthedustexplosioncharacteristicsand completingthecurrentdustexplosioncharacteristicstestandsafetydesign.
Inordertopreventandcontrolindustrialdustexplosionandimprovetheaccuracyofdust explosiontests,anexperimentalresearchwascarriedouttohaveaninsightintotheexplosionbehaviorofhigh- andlow-volatiledustsinducedbydifferentignitionenergiesbyusingaSiwek20Lsphericalexplosiontestsystem. Ignitionenergyeffectondustexplosionbrisance(max.explosionpressure, max.pressurerisingrateandcombustionduration)andsensitivity (lowerexplosionlimit)andthe variationofexplosionsuppressioneffectivenessofinertsubstancealongwiththeignitionenergywere explored.Resultsshowthathigherignitionenergyimprovestheexplosionenergyreleaseandcombustionrateofdustcloud; theeffectofignitionenergyonexplosionbehaviorismoresignificantforless volatiledust.Incompletedeflagrationoflow-volatiledustundertheconditionoflowignitionenergy resultsintheadverseeffectofexplosion.Theadverseeffectofexplosionbecomesinconspicuousas thedustconcentrationincreases.Thelowerexplosionlimitdecreasessharplywiththeriseofignition energyforlow-volatiledust,whilethelowerexplosionlimitofhigh-volatiledustisnotsosensitiveto ignitionenergy.Moreover,explosionsuppressioneffectivenessofinertsubstancedecreaseswiththe riseofignitionenergy.Theignitionenergyof5~10kJisthemostappropriateforunderstandingthe lowerexplosionlimitoflow-volatiledustandtheexplosionsuppressioneffectivenessofinertsubstance. Theaboveresultsmaybevaluableforunderstandingthedustexplosioncharacteristicsand completingthecurrentdustexplosioncharacteristicstestandsafetydesign.
2012, 32(4): 439-444.
doi: 10.11883/1001-1455(2012)04-0439-06
Abstract:
Aexperimentsofdownholeperforationandfracturingpressurelivetestbasedoncoppercylinderandcorrespondingp- tcurvesatthesametimewereperformed.A mathematicalmodelforcoppercylindergaugeswasdevelopedandobtainedtheanalyticalsolutionofitsworkingprocesswasobtainedbyusinganin eractivecalculationmethod.Theresultsshowthatthetestvalue,whichcopper cylindergotindownholeperforationandfracturing,maybelargerthanthetruevalueorbesmaller, mainlydependingonthepressurerisetime,pulse width,peakpressureandotherfactors.The processofdownholeperforationandfracturingisdifferentfromartillerychamberpressure,thepressurerisetimeisshort. Velocityofthepistonisstilllargewhenexternalpressurepassedthepeakand thepistonwillcontinuecompressthecylinderuntilitsvelocityreducedtozero.Inthisprocess,the pistoncanbedividedintotwoparts:Rapidaccelerationanddecelerationduringimpact.Themaximumvalueofpistonvelocityisdeterminantsforthefinaltest, thegreaterthespeedthegreaterthe testvalue,Itisproposedthatcoppercylinderpressure-measuringgaugewithlightqualitypistonbe developedtoreducecoppercylindertesterrorinthiscase.
Aexperimentsofdownholeperforationandfracturingpressurelivetestbasedoncoppercylinderandcorrespondingp- tcurvesatthesametimewereperformed.A mathematicalmodelforcoppercylindergaugeswasdevelopedandobtainedtheanalyticalsolutionofitsworkingprocesswasobtainedbyusinganin eractivecalculationmethod.Theresultsshowthatthetestvalue,whichcopper cylindergotindownholeperforationandfracturing,maybelargerthanthetruevalueorbesmaller, mainlydependingonthepressurerisetime,pulse width,peakpressureandotherfactors.The processofdownholeperforationandfracturingisdifferentfromartillerychamberpressure,thepressurerisetimeisshort. Velocityofthepistonisstilllargewhenexternalpressurepassedthepeakand thepistonwillcontinuecompressthecylinderuntilitsvelocityreducedtozero.Inthisprocess,the pistoncanbedividedintotwoparts:Rapidaccelerationanddecelerationduringimpact.Themaximumvalueofpistonvelocityisdeterminantsforthefinaltest, thegreaterthespeedthegreaterthe testvalue,Itisproposedthatcoppercylinderpressure-measuringgaugewithlightqualitypistonbe developedtoreducecoppercylindertesterrorinthiscase.
2012, 32(4): 445-448.
doi: 10.11883/1001-1455(2012)04-0445-04
Abstract:
Experimentalinvestigationonthelimitoxygenvolumefraction,explosionlimitandexplosionsuppressioneffectofmethanewascarriedoutbyaddingN2/ CO2 mixtureintomethane-airmixture. ResultsshowthatthelimitoxygenvolumefractiondecreaseslinearlywiththeincrementofN2 inN2/CO2 mixture.Theinfluenceofvariouscompositionsofinertgasesonexplosionlimitofmethanemixturecanbeconsideredtobelinear. ThehigherthecompositionratiosofCO2inN2/CO2 mixture, thebettertheexplosionsuppressionformethane.Besides,theobtainedfittedequationcanpredictmethaneexplosionlimitsinanycompositionratiosofN2/ CO2 mixture.Theaboveresultscanbe usedasareferenceforexplosionprotectiondesigninengineering.
Experimentalinvestigationonthelimitoxygenvolumefraction,explosionlimitandexplosionsuppressioneffectofmethanewascarriedoutbyaddingN2/ CO2 mixtureintomethane-airmixture. ResultsshowthatthelimitoxygenvolumefractiondecreaseslinearlywiththeincrementofN2 inN2/CO2 mixture.Theinfluenceofvariouscompositionsofinertgasesonexplosionlimitofmethanemixturecanbeconsideredtobelinear. ThehigherthecompositionratiosofCO2inN2/CO2 mixture, thebettertheexplosionsuppressionformethane.Besides,theobtainedfittedequationcanpredictmethaneexplosionlimitsinanycompositionratiosofN2/ CO2 mixture.Theaboveresultscanbe usedasareferenceforexplosionprotectiondesigninengineering.
