作者:标准资料网 时间:2024-04-30 10:23:59   浏览:9896   来源:标准资料网

【英文标准名称】:StandardTestMethodforTwistinYarnsbyDirect-Counting
【原文标准名称】:直接计数法测定纱线捻数的标准试验方法
【标准号】:ASTMD1423-2002(2008)
【标准状态】:现行
【国别】:美国
【发布日期】:2002
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:D13.58
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:
【英文主题词】:twist;twistfactor;twistmultiplier;twisttake-up;yarn;Direct-countingtechnique;Twist--textiles
【摘要】:TestMethodD1423fortestingtwistinyarnsbydirect-countingisconsideredsatisfactoryforacceptancetestingofcommercialshipmentsbecausecurrentestimatesofbetween-laboratoryprecisionareacceptableandthemethodhasbeenusedextensivelyinthetradeforacceptancetesting.Iftherearedifferencesofpracticalsignificancebetweenreportedtestresultsfortwolaboratories(ormore),comparativetestsshouldbeperformedtodetermineifthereisastatisticalbiasbetweenthem,usingcompetentstatisticalassistance.Asaminimumusethesamplesforsuchcomparativetestsashomogeneousaspossible,drawnfromthesamelotofmaterialthatresultedinthedisparatetestresultsandrandomlyinequalnumberstoeachlaboratory.Thetestresultsfromthelaboratoriesinvolvedshouldbecomparedusingastatisticaltestforunpaireddata,ataprobabilitylevelchosenpriortothetestingseries.Ifabiasisfound,eitheritscausemustbefoundandcorrected,orfuturetestresultsforthatmaterialmustbeadjustedinconsiderationoftheknownbias.Thedeterminationoftwistinastraightsectionofayarnisnotthesimplestraightforwardoperationitappearstobe,forthetestresultsmaybegreatlyinfluencedbyvariationsintestproceduresandtechniques.Inallmanipulations,extremecareisnecessarytopreventspecimenrotationalteringthetwistlevelbeforetestingbegins.Thetwistinayarnbeforeitispackagedmaybedifferentfromthatoftheyarnafterithasbeenwithdrawnfromthepackagebecauseofchangesintensionandtheeffectofthemethodofwithdrawal.Iftheyarniswithdrawnover-end,aslightincreaseordecreaseintwistwilltakeplace,dependinguponthedirectionofthetwistintheyarn,thedirectionofwindingonthepackage,andthelengthofthewraponthepackage.Whenayarnisincorporatedintoorremovedfromamorecomplexstructure,alterationsmayoccurasaresultoftheplying,untwisting,orravelingoperation.Forexample,whendeterminingthetwistinpliedyarnbytheprocedurefordeterminingoriginaltwist,asthepliedyarnisuntwisted,acomparableamountoftwistisreinsertedin,orremovedfrom,thesingle-yarncomponents.Asaconsequence,thesingleyarnshaveapproximatelytheoriginaltwistpriortotheplyingoperationbutnotthetwisttheyhavewhentheyarefunctioningascomponentsofthepliedyarn.Thelatterorfinaltwistmaybeestimatedbyaddingtheplytwistto(orsubtractingitfrom)thesingle-yarntwistdependingonthedirectionsoftheplyandsinglestwist.Foramoreprecisedetermination,thetestproceduremustbemodified.Therearethustwodifferentproceduresforpreparingspecimensofthecomponentelementsofapliedorcabledyarnfortwistdetermination.Theprocedurefortheoriginaltwistmeasuresthetwistinacomponentofacomplexstrandafterthecomponentshavebeenuntwisted.Theprocedureforfinaltwistmeasuresthetwistinacomponentasitliesinthecomplexstrand.Althoughtheoriginaltwistprocedureismostoftenused,selectionofaparticularprocedurewilldependonthetypeofinformationneeded.Note38212;Thedifferenceintwistbetweenunwindingfromthesideandover-endis1/x03C0;d,wheredisthediameterofthepackage.Thus,fora25-mm(1-in.)diameterpackage,thedifferencewouldbeabout13tpmorabout1/3tpi.Whenayarnistakenfromamorecomplexyarnstructureorfromafabric,theresultanttwistshouldbeconsideredonlyanapproximationoftheoriginalvaluebecauseofalterationsthatmayhaveoccurredasaresultoftheeffectsofunwinding,handling,andmechanicalstrainsmetinprocessing.Theoptimumamountoftwistdependsupon........
【中国标准分类号】:W58
【国际标准分类号】:59_080_20
【页数】:7P.;A4
【正文语种】:英语