简介:Thispaperstudiesthree-dimensionaldiffractionofobliquelyincidentplaneSHwavesbytwininfinitelylongcylindricalcavitiesinlayeredporoelastichalf-spaceusingindirectboundaryelementmethod.Theapproachisvalidatedbycomparisonwiththeliterature,andtheeffectsofcavityinterval,incidentfrequency,andboundarydrainageconditiononthediffractionarestudiedthroughnumericalexamples.Itisshownthat,theinteractionbetweentwocavitiesissignificantandsurfacedisplacementpeaksbecomelargewhentwocavitiesareclose,andthesurfacedisplacementmaybesignificantlyamplifiedbytwincavities,andtheinfluencerangewithlargeamplificationcanbeaswideas40timesofthecavityradius.Surfacedisplacementsindryporoelasticcaseandsaturatedporoelasticcaseswithdrainedandundrainedboundariesareevidentlydifferentundercertaincircumstances,andthedifferencesmaybemuchlargerthanthoseinthefree-fieldresponse.
简介:ThedetailedmicrostructuresofNi80Fe20/Fe50Mn50superlatticeshavebeencharacterizedusingbothx-raydiffractiontechniquesandtransmissionelectronmicroscopy.Theobrivouslayeredstructure,typicalcolumnstructureandtwinswhichexistinNi80Fe20/Fe50Mn50superlatticeswereobservedthroughperformingtransmissionmicroscopy.Bycombiningthetechniqueoflowanglex-rayreflectivity(specularandoff-specularscans)withtheanomalousscatteringeffectandhigh-anglex-raydiffraction(usingconventionalx-ray),wequantitativelyanalysedthemicrostructuralvariationasafunctionofannealingtemperature.Itisfoundthatthelateralcorrelationlength,the(111)peakintensityofthesuperlatticesandtheaveragemultilayercoherencelengthallincreasewithariseinannealingtemperatureannealingcandecreasetherootmean-squareroughnessattheinterfacesofNi80Fe20/Fe50Mn50superlattices.theobtainedmicrostructuralknowledgewillbehelpfulinunderstandingthemagneticpropertiesoftheni80Fe20/Fe50Mn50exchangebiassystem.
简介:Inthepresentpaper,two-andthree-dimensionalvelocitypotentialsgeneratedbypulsatingpressuredistributionsofinfiniteextentonthefreesurfaceofinfinite-depthwatersarestrictlyderivedbasedonspecialcasesofconcentratedpulsatingpressure.Thefar-fieldasymptoticbehaviourofthepotentialsandtheradiationconditionstobesatisfiedbythemarediscussed.Itisprovedinageneralsensethatthepotentialsshouldbecomposedofaforcedwavecomponent,afreewavecomponentandalocaldisturbancecomponent.Theradiationconditionoftheforcedwavecomponentshouldcorrespondtothefar-fieldasymptoticbehaviourofthepressuredistribution,Hence,theformulationofradiationconditionsforthesecond-orderdiffractionpotentialshastheoreticallybecomeclear,Theradiationconditionsfortwo-andthree-dimensionalproblemsareexplicitlygiveninthepaper.
简介:Twinninganddetwinningaretheimportantdeformationmodesinmagnesiumalloysduringcyclicloadingatroomtemperature.Toanalyzethesetwodeformationmechanism,cycliccompression–tensionexperimentswereperformedonMg–3Al–1Znrolledsheetalongtherollingdirection.Inthesetests,themicrostructureevolutionsofaseriesofgrainsduringdeformationweretracedbyusingquasiinsituelectronbackscatterdiffraction(EBSD).ImportantquantitiesliketheSchmidfactorsoftwinningsystem,thefractionoftwinningduringcompression,andthefractionoftwinningafterreverseloadingwerecalculatedonthebasisofmeasuredquantities.TheinfluenceofSchmidfactoroftwinningvariantsondetwinninguponreverseloadingwasanalyzed.DetwinningwouldprefertoproceedduringreverseloadingiftheSchmidfactoroftwinninginthetwinningareabeforereverseloadingissufficientlylarge.