ASTM_D_1780_-_05_2020.pdf

Designation:D178005(Reapproved 2020)Standard Practice forConducting Creep Tests of Metal-to-Metal Adhesives1This standard is issued under the fixed designation D1780;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 This practice covers the determination of the amount ofcreep of metal-to-metal adhesive bonds due to the combinedeffects of temperature,tensile shear stress,and time.NOTE1Since the characteristics that render a material resistant tocreep under the condition of test are not yet completely known,the detailsof the procedure considered herein are those known to have importantinfluences.Since other equally important characteristics may be discov-ered in the future,the recommended details are largely advisory in nature.1.2 Test periods depend upon the reasonable life expectedfrom the material in service.The uncertainties of extrapolationshould be considered in deciding upon the length of the test.1.3 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.4 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D907 Terminology of AdhesivesD1002 Test Method for Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Specimens by Ten-sion Loading(Metal-to-Metal)3.Terminology3.1 DefinitionsMany of the terms in this practice aredefined in Terminology D907.3.2 Definitions of Terms Specific to This Standard:3.2.1 creep,nthe time-dependent part of the strain thatresults from exposure to a constant temperature and load(Note2).That is,the creep at a given elapsed time is equal to the totalstrain at the given time minus the instantaneous strain(Note 3)on loading.The creep extension is expressed as a percentage,that is,the extension divided by the initial unstretched lengthmultiplied by 100.NOTE2Constant-stress creep tests are desirable.The usual one is aconstant deadweight load test.Creep tests made by means of springloading or fixtures which involve deflection or strain measurements in thefixture for the application of load are unsatisfactory.However,if the totaldeformation or extension in the adhesive is large,corrections must bemade to compensate for the decrease in stress because of the extension inthe adhesive.NOTE3Since the time-dependent strain develops rapidly even duringthe application of the load,the instantaneous strain for recovery is usuallydifficult to determine,except in the arbitrary manner given in thedefinitions of instantaneous strain and instantaneous recovery.3.2.2 deformation,nthe total strain at any specific time.3.2.3 failure,nrupture of the specimen,or exceeding thestrain requirements of a specific design.3.2.4 instantaneous recovery,nthe decrease in strain oc-curring immediately upon unloading a specimen.As in instan-taneous strain,a more reproducible value is obtained if thedecrease in strain is measured after a given small increment oftime(such as 1 min)following unloading.The increment oftime used shall be specified.The instantaneous recovery shallbe expressed in the same units as strain,that is,the decrease inlength divided by the gage length usually,in inches per inch.3.2.5 instantaneous strain,nthe strain occurring immedi-ately upon loading a creep specimen.Since it is nearlyimpossible to obtain strain readings at the instant of loading,the strain after a given small increment of time(such as 1 min)after loading is a more reproducible value.The increment oftime used shall be specified.The instantaneous strain shall beexpressed in the units as strain,that is,the extension divided bythe gage length,usually in inches per inch.1This practice is under the jurisdiction of ASTM Committee D14 on Adhesivesand is the direct responsibility of Subcommittee D14.80 on Metal BondingAdhesives.Current edition approved Dec.15,2020.Published December 2020.Originallyapproved in 1960.Last previous edition approved in 2012 as D1780 05(2012).DOI:10.1520/D1780-05R20.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMS