ASTM_C_1377_-_97_2009.pdf

Designation:C137797(Reapproved 2009)Standard Test Method forCalibration of Surface/Stress Measuring Devices1This standard is issued under the fixed designation C1377;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers calibration or verification ofcalibration,or both,of surface-stress measuring devices used tomeasure stress in annealed and heat-strengthened or temperedglass using polariscopic or refractometry based principles.1.2 This test method is nondestructive.1.3 This test method uses transmitted light,and therefore,isapplicable to light-transmitting glasses.1.4 This test method is not applicable to chemically tem-pered glass.1.5 Using the procedure described,surface stresses can bemeasured only on the“tin”side of float glass.1.6 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.7 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:2C158 Test Methods for Strength of Glass by Flexure(De-termination of Modulus of Rupture)C162 Terminology of Glass and Glass ProductsC770 Test Method for Measurement of Glass StressOptical CoefficientC1048 Specification for Heat-Strengthened and Fully Tem-pered Flat GlassC1279 Test Method for Non-Destructive Photoelastic Mea-surement of Edge and Surface Stresses in Annealed,Heat-Strengthened,and Fully Tempered Flat Glass3.Terminology3.1 DefinitionsFor terminology used in this test method,refer to Terminology C162.4.Summary of Test Method4.1 In this test method,a test bar is subjected to bendingusing deadweights or calibrated load-cells to introduce surfacestresses that can be calculated from the specimen geometry andforces applied.At a point in which the stresses are calculated,those same stresses also are measured using the instrument tobe calibrated or verified.Since both the specimen dimensionand the applied forces can be established accurately usingtraceable(primary)standards,the method permits a fullytraceable calibration of the stress-measuring instrument.5.Significance and Use5.1 The strength and performance of heat-strengthened andfully tempered glass is greatly affected by the surface and edgestress induced during the heat-treating process.5.2 The edge and surface stress levels are specified inSpecification C1048,in the Engineering Standards Manual ofGANA3,and in foreign specifications.5.3 Surface stresses can be measured nondestructively usingmethods,such as Test Method C1279.The calibration ofsurface measuring devices used in those procedures andperiodic verification of calibration are needed.This test methodoffers a convenient way to accomplish this task.6.Principle of Operation6.1 The instrument to be calibrated is placed on the surfaceof the calibration specimen.Stresses at a point where theinstrument is placed are calculated using expressions shown inSection 9.To increase the precision of measurement,severallevels of stress are produced by applying forces incrementally.Measurement of stress using the instrument to be calibrated isrepeated for each stress level and these measurements are usedto calibrate the instrument.1This test method is under the jurisdiction of ASTM Committee C14 on Glassand Glass Products and is the direct responsibility of Subcommittee C14.08 on FlatGlass.Current edition approved May 1,2009.Published September 2009.Originallyapproved in 1997.Last previous edition approved in 2003 as C1377 97(2003).DOI:10.1520/C1377-97R09.2For 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.3Available from GANA,Glass Association of North America,3310 SWHarrison St.,Topeka,KS 666112279.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesNOTICE:This standard has either been superseded and replaced by a new version or withdrawn.Contact ASTM International(www.astm.org)for the latest information1 7.Test Specimens and Loading SchemesTwo loading geometries can be practiced:cantilever andfour-point bending.7.1 Cantilever-Beam Specimen(Fig.1)the dimensions ofthe specimen used for cantilever loading should be selectedwithin limits shown below:Thickness(t):0.22 in.(6 mm)minimumWidth(w):8t#w#12tLength(L):6w minimumDistance to the point of measu