Designation:C978−04(Reapproved2019)StandardTestMethodforPhotoelasticDeterminationofResidualStressinaTransparentGlassMatrixUsingaPolarizingMicroscopeandOpticalRetardationCompensationProcedures1ThisstandardisissuedunderthefixeddesignationC978;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodcoversthedeterminationofresidualstressesinatransparentglassmatrixbymeansofapolarizingmicroscopeusingnullorretardationcompensationprocedures.1.2Suchresidualstressdeterminationsareofimportanceinevaluatingthenatureanddegreeofresidualstressespresentinglassmatrixesduetocord,orthedegreeoffit,orsuitabilityofaparticularcombinationofglassmatrixandenamel,orappliedcolorlabel(ACL).1.3Theretardationcompensationmethodofopticallyde-terminingandevaluatingenamelorACLresidualstresssys-temsoffersdistinctadvantagesovermethodsrequiringphysi-calpropertymeasurementsorwareperformancetestsduetoitssimplicity,reproducibility,andprecision.1.4Limitations—Thistestmethodisbasedonthestress-opticalretardationcompensationprinciple,andisthereforeapplicableonlytotransparentglasssubstrates,andnottoopaqueglasssystems.1.5Duetothepossibilityofadditionalresidualstressesproducedbyionexchangebetweenglassesofdifferentcompositions,someuncertaintymaybeintroducedinthevalueofthestressopticalcoefficientinthepointofinterestduetoalackofaccurateknowledgeofchemicalcompositionintheareasofinterest.1.6Thistestmethodisquantitativelyapplicabletoandvalidonlyforthoseapplicationswheresuchsignificantionexchangeisnotafactor,andstressopticalcoefficientsareknownordeterminable.1.7Theextentoftheionexchangeprocess,andhencethemagnitudesoftheresidualstressesproducedduetoionexchangewilldependontheexchangeprocessparameters.Theresidualstressdeterminationsmadeonsystemsinwhichionexchangehasoccurredshouldbeinterpretedwithth...
