ASTM_C_158_-_02_2012.pdf

Designation:C15802(Reapproved 2012)Standard Test Methods forStrength of Glass by Flexure(Determination of Modulus ofRupture)1This standard is issued under the fixed designation C158;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 These test methods cover the determination of themodulus of rupture in bending of glass and glass-ceramics.1.2 These test methods are applicable to annealed andprestressed glasses and glass-ceramics available in variedforms.Alternative test methods are described;the test methodused shall be determined by the purpose of the test andgeometric characteristics of specimens representative of thematerial.1.2.1 Test Method A is a test for modulus of rupture of flatglass.1.2.2 Test Method B is a comparative test for modulus ofrupture of glass and glass-ceramics.1.3 The test methods appear in the following order:SectionsTest Method ATest Method B6 to 910 to 151.4 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.Specific hazardstatements are given in Section 10 and A1.5,A2.3.3,A2.4.3and A2.5.3.2.Referenced Documents2.1 ASTM Standards:2C148 Test Methods for Polariscopic Examination of GlassContainersE4 Practices for Force Verification of Testing MachinesSI10-02 IEEE/ASTM SI 10 American National Standard forUse of the International System of Units(SI):The ModernMetric System3.Terminology3.1 Definitions:3.1.1 glass-ceramicssolid materials,predominantly crys-talline in nature,formed by the controlled crystallization ofglasses.3.1.2 modulus of rupture in bendingthe value of maxi-mum tensile or compressive stress(whichever causes failure)in the extreme fiber of a beam loaded to failure in bendingcomputed from the flexure formula:Sb5M cI(1)where:M=maximum bending moment,computed from the maxi-mum load and the original moment arm,c=initial distance from the neutral axis to the extreme fiberwhere failure occurs,andI=initial moment of inertia of the cross section about theneutral axis.3.1.3 prestressedmaterial in which a significant and con-trolled degree of compressive stress has been deliberatelyproduced in the surfaces.3.1.4 standard laboratory atmospherean atmosphere hav-ing a temperature of 23 6 2C and a relative humidity of 40 610%.3.2 Definitions of Terms Specific to This Standard:3.2.1 abradeddescribes a test specimen that has at least aportion of the area of maximum surface tensile stress subjectedto an operationally defined procedure for mechanical abrasion.The severity and uniformity of abrasion should be sufficient toensure origin of failure substantially in the region of maximumstress.3.2.2 annealed glassdescribes a specimen that shall nothave a temper or degree of residual stress resulting from priorthermal treatment in excess of the following limits whenmeasured polarimetrically(see Annex A1):1These test methods are under the jurisdiction of ASTM Committee C14 onGlass and Glass Products and are the direct responsibility of Subcommittee C14.04on Physical and Mechanical Properties.Current edition approved Oct.1,2012.Published October 2012.Originallyapproved in 1940.Last previous edition approved in 2002 as C158 02(2007).DOI:10.1520/C0158-02R12.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.2.1 Specimens of rectangular section shall not have atensile stress at the midplane of more than 1.38-MPa(200-psi)nor more than 2.76-MPa(400-psi)compression at the surface.3.2.2.2 Specimens in rod form may be examined by viewingthrough a diameter at least four diameters from an end.Theapparent central axial tension shall not exceed 0.92 MPa(133psi).Surface compression,if measured on sections cut from therods,shall not exceed 2.76 MPa(400 psi)when viewed axially.4.Significance and Use4.1 For the purpose of this test,glasses and glass-ceramicsare considered brittle(perfectly elastic)and to have theproperty that fracture normally occurs at the surface of the testspecimen from the principal tensile stress.The modulus ofrupture is considered a valid measure of the tensile strengthsubject to the considerations discussed below.4.2 It is recognized that the modulus of rupture for a groupof test specimens is influenced by variables associated with thetest pr