ASTM_G_30_-_97_2015.pdf

Designation:G3097(Reapproved 2015)Standard Practice forMaking and Using U-Bend Stress-Corrosion TestSpecimens1This standard is issued under the fixed designation G30;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 practice covers procedures for making and usingU-bend specimens for the evaluation of stress-corrosion crack-ing in metals.The U-bend specimen is generally a rectangularstrip which is bent 180 around a predetermined radius andmaintained in this constant strain condition during the stress-corrosion test.Bends slightly less than or greater than 180 aresometimes used.Typical U-bend configurations showing sev-eral different methods of maintaining the applied stress areshown in Fig.1.1.2 U-bend specimens usually contain both elastic andplastic strain.In some cases(for example,very thin sheet orsmall diameter wire)it is possible to form a U-bend andproduce only elastic strain.However,bent-beam(Practice G39or direct tension(Practice G49)specimens are normally usedto study stress-corrosion cracking of strip or sheet under elasticstrain only.1.3 This practice is concerned only with the test specimenand not the environmental aspects of stress-corrosion testingwhich are discussed elsewhere(1)2and in Practices G35,G36,G37,G41,G44,G103 and Test Method G123.1.4 The values stated in SI units are to be regarded asstandard.The inch-pound units in parentheses are provided forinformation.1.5 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:3E3 Guide for Preparation of Metallographic SpecimensG1 Practice for Preparing,Cleaning,and Evaluating Corro-sion Test SpecimensG15 Terminology Relating to Corrosion and Corrosion Test-ing(Withdrawn 2010)4G35 Practice for Determining the Susceptibility of StainlessSteels and Related Nickel-Chromium-Iron Alloys toStress-Corrosion Cracking in Polythionic AcidsG36 Practice for Evaluating Stress-Corrosion-Cracking Re-sistance of Metals and Alloys in a Boiling MagnesiumChloride SolutionG37 Practice for Use of Mattssons Solution of pH 7.2 toEvaluate the Stress-Corrosion Cracking Susceptibility ofCopper-Zinc AlloysG39 Practice for Preparation and Use of Bent-Beam Stress-Corrosion Test SpecimensG41 Practice for Determining Cracking Susceptibility ofMetals Exposed Under Stress to a Hot Salt EnvironmentG44 Practice for Exposure of Metals andAlloys byAlternateImmersion in Neutral 3.5%Sodium Chloride SolutionG49 Practice for Preparation and Use of Direct TensionStress-Corrosion Test SpecimensG103 Practice for Evaluating Stress-Corrosion Cracking Re-sistance of Low Copper 7XXX Series Al-Zn-Mg-CuAlloys in Boiling 6%Sodium Chloride SolutionG123 Test Method for Evaluating Stress-Corrosion Crackingof Stainless Alloys with Different Nickel Content inBoiling Acidified Sodium Chloride Solution1This 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 Nov.1,2015.Published November 2015.Originallyapproved in 1972.Last previous edition approved in 2009 as G3097(2009).DOI:10.1520/G0030-97R15.2The 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.4The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.Terminology3.1 For definitions of corrosion-related terms used in thispractice see Terminology G15.4.Summary of Practice4.1 This practice involves the stressing of a specimen bentto a U shape.The applied strain is estimated from the bendconditions.The stressed specimens are then exposed to the testenvironment and the time required for cracks to develop isdetermined.This cracking time is used as an estimate of thestress corrosion resistance of the material in the test environ-ment.5.Significance and Use5.1 The U-bend specimen may be used for any metal alloysufficiently ductile to be formed into the U-shape withoutmechanically cracking.The specimen is most easily made fromstrip or sheet but can be machined from plate,bar,castings,orweldments;wire specimens may be used also.5.2 Since the U-bend usually contains large amounts ofelastic and plasti