ASTM_G_39_-_99_2011.pdf

Designation:G3999(Reapproved 2011)Standard Practice forPreparation and Use of Bent-Beam Stress-Corrosion TestSpecimens1This standard is issued under the fixed designation G39;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 Thispracticecoversproceduresfordesigning,preparing,and using bent-beam stress-corrosion specimens.1.2 Different specimen configurations are given for use withdifferent product forms,such as sheet or plate.This practiceapplicable to specimens of any metal that are stressed to levelsless than the elastic limit of the material,and therefore,theapplied stress can be accurately calculated or measured(seeNote 1).Stress calculations by this practice are not applicableto plastically stressed specimens.NOTE1It is the nature of these practices that only the applied stresscan be calculated.Since stress-corrosion cracking is a function of the totalstress,for critical applications and proper interpretation of results,theresidual stress(before applying external stress)or the total elastic stress(after applying external stress)should be determined by appropriatenondestructive methods,such as X-ray diffraction(1).21.3 Test procedures are given for stress-corrosion testing byexposure to gaseous and liquid environments.1.4 The bent-beam test is best suited for flat product forms,such as sheet,strip,and plate.For plate material the bent-beamspecimen is more difficult to use because more rugged speci-men holders must be built to accommodate the specimens.Adouble-beam modification of a four-point loaded specimen toutilize heavier materials is described in 10.5.1.5 The exposure of specimens in a corrosive environmentis treated only briefly since other practices deal with thisaspect,for example,Specification D1141,and Practices G30,G36,G44,G50,and G85.The experimenter is referred toASTM Special Technical Publication 425(2).1.6 The bent-beam practice generally constitutes a constantstrain(deflection)test.Once cracking has initiated,the state ofstress at the tip of the crack as well as in uncracked areas haschanged,and therefore,the known or calculated stress or strainvalues discussed in this practice apply only to the state of stressexisting before initiation of cracks.1.7 The values stated in SI units are to be regarded asstandard.The inch-pound values in parentheses are providedfor information.1.8This 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.(For more specificsafety hazard information see Section 7 and 12.1.)2.Referenced Documents2.1 ASTM Standards:3D1141 Practice for the Preparation of Substitute OceanWaterG30 Practice for Making and Using U-Bend Stress-Corrosion Test SpecimensG36 Practice for Evaluating Stress-Corrosion-Cracking Re-sistance of Metals and Alloys in a Boiling MagnesiumChloride SolutionG44 Practice for Exposure of Metals andAlloys byAlternateImmersion in Neutral 3.5%Sodium Chloride SolutionG50 Practice for Conducting Atmospheric Corrosion Testson MetalsG85 Practice for Modified Salt Spray(Fog)Testing2.2 NACE Documents:4NACE TM0177-96 Laboratory Testing of Metals for Resis-tance to Specific Forms of Environmental Cracking in H2SEnvironments3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 cracking timethe time elapsed from the inception oftest until the appearance of cracking.1This practice is under the jurisdiction of ASTM Committee G01 on Corrosionof Metals and is the direct responsibility of Subcommittee G01.06 on Environmen-tally Assisted Cracking.Current edition approved March 1,2011.Published April 2011.Originallyapproved in 1973.Last previous edition approved in 2005 as G3999(2005).DOI:10.1520/G0039-99R11.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.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.4Available from NACE International(NACE),1440 South Creek Dr.,Houston,TX 77084-4906,http:/www.nace.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.1.1.1 DiscussionThe test begins when the stress isapplied and the stressed specimen is exposed to the corrosiveenvironment,whichever occurs later.3.1.1.2 DiscussionThe specimen is considered to havefailed when cracks are detected.Presence of cracks can bedetermined with or without optical,mechanical,or electronicaids.However,for meaningful interpretation,comp