Designation:C770−16StandardTestMethodforMeasurementofGlassStress—OpticalCoefficient1ThisstandardisissuedunderthefixeddesignationC770;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodcoversproceduresfordeterminingthestress-opticalcoefficientofglass,whichisusedinphotoelasticanalyses.InProcedureAtheopticalretardationisdeterminedforaglassfibersubjectedtouniaxialtension.InProcedureBtheopticalretardationisdeterminedforabeamofglassofrectangularcrosssectionwhensubjectedtofour-pointbending.InProcedureC,theopticalretardationismeasuredforabeamofglassofrectangularcross-sectionwhensubjectedtouniaxialcompression.1.2Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2C336TestMethodforAnnealingPointandStrainPointofGlassbyFiberElongationC598TestMethodforAnnealingPointandStrainPointofGlassbyBeamBendingC1426PracticesforVerificationandCalibrationofPolarim-etersF218TestMethodforMeasuringOpticalRetardationandAnalyzingStressinGlass2.2NIST,RecommendedPracticeGuide“FractographyofCe-ramicsandGlasses”(Section4.6.2—FlexuralStrength)3.SignificanceandUse3.1Stress-opticalcoefficientsareusedinthedeterminationofstressinglass.Theyareparticularlyusefulindeterminingthemagnitudeofthermalresidualstressesforannealingorpre-stressing(tempering)glass.Assuch,theycanbeimportantinspecificationacceptance.4.Apparatus4.1StressingEquipmentandPolarimeter:4.1.1ProcedureA—Figs.1and2illustrateapolarimeteremployingaquarter-waveplateandrotatableanalyzer,3de-scribedinTestMethodF218.Thequarter-waveplateshallbedesignedforthewavelengthofthelightbeingused.Thepolarizi...
