ASTM_F_218_-_13.pdf

Designation:F21813Standard Test Method forMeasuring Optical Retardation and Analyzing Stress inGlass1This standard is issued under the fixed designation F218;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the analysis of stress in glass bymeans of a polarimeter based on the principles developed byJessop and Friedel(1,2).2Stress is evaluated as a function ofoptical retardation,that is expressed as the angle of rotation ofan analyzing polarizer that causes extinction in the glass.1.2 There is no known ISO equivalent to this standard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:3C162 Terminology of Glass and Glass ProductsC770 Test Method for Measurement of Glass StressOptical CoefficientC978 Test Method for Photoelastic Determination of Re-sidual Stress in a Transparent Glass Matrix Using aPolarizing Microscope and Optical Retardation Compen-sation ProceduresC1426 Practices for Verification and Calibration of Polarim-etersE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE177 Practice for Use of the Terms Precision and Bias inASTM Test Methods3.Terminology3.1 For definitions of terms used in this standard,refer toTerminology C162.4.Significance and Use4.1 The performance of glass products may be affected bypresence of residual stresses due to process,differential ther-mal expansion between fused components,and by inclusions.This test method provides means of quantitative evaluation ofstresses.5.Calibration and Standardization5.1 Whenever calibration of the polarimeter is required byproduct specification,Practices C1426 for verification andcalibration should be used.6.Polarimeter6.1 The polarimeter shall consist of an arrangement similarto that shown in Fig.1.A description of each componentfollows:6.1.1 Source of LightEither a white light or a monochro-matic source such as sodium light(589 nm)or a white lightcovered with a narrow-band interferential filter B,(see Fig.1,)transmitting the desired monochromatic wavelength.NOTE1The white light should provide a source of illumination withsolar temperature of at least that of Illuminant A.6.1.2 FilterThe filter should be placed between the lightsource and the polarizer,or between the analyzer and theviewer(see Fig.1).6.1.3 DiffuserA piece of opal glass or a ground glass ofphotographic quality.6.1.4 PolarizerA polarizing element housed in a rotatablemount capable of being locked in a fixed position shown inFig.2 and Fig.4.6.1.5 Immersion CellRectangular glass jar with strain-free,retardation-free viewing sides filled with a liquid havingthe same index of refraction as the glass specimen to bemeasured.It may be surmounted with a suitable device forholding and rotating the specimen,such that it does not stressthe specimen.NOTE2Suitable index liquids may be purchased or mixed as required.Dibutyl phthalate(refractive index 1.489),and tricresyl phosphate(index1.555)may be mixed to produce any desired refractive index between thetwo limits,the refractive index being a linear function of the proportion ofone liquid to the other.Other liquids that may be used are:1This test method is under the jurisdiction of ASTM Committee C14 on Glassand Glass Products and is the direct responsibility of Subcommittee C14.04 onPhysical and Mechanical Properties.Current edition approved Oct.1,2013.Published October 2013.Originallyapproved in 1950.Last previous edition approved in 2012 as F218 12.DOI:10.1520/F0218-13.2The boldface numbers in parentheses refer to the reports and papers appearingin the list of references at the end of this test method.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 LiquidRefractive IndexCinnamic aldehyde1.62Oil of cassia1.61Monochlorobenzene1.525Carbon tetrachloride1.463Dipentene(Eastman)1.473NOTE3Cases may arise where the refraction liquid may contaminatethe specimen.When the sample is viewed through faces that areessentially parallel,elimination of the liquid will cause only a minor error.However,when viewing through faces of the sample that are not parallel,the use of liquid of same refraction index is essential.6.1.6 Full-Wave(Sensitive Tint)Plate,having a retardationof 565 6