1、Designation: E2818 11Standard Practice forDetermination of Quasistatic Fracture Toughness of Welds1This standard is issued under the fixed designation E2818; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision
2、. 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 practice provides methods for preparing specimensfrom welds in metallic materials and interpreting subsequenttest results when
3、 used in conjunction with standards TestMethods E1290 and E1820 for the determination of fracturetoughness. The fatigue pre-cracking procedures included inthis practice may also be used to aid in preparing straightpre-cracks for weld specimens in accordance with Test MethodE1681.1.2 This practice dr
4、aws heavily from ISO 15653: Metallicmaterials Method of test for the determination of quasistaticfracture toughness of welds. All references to ISO 12135 inthat test method should be replaced with the applicable ASTMTest Methods (E1820, E1290 or E1681).1.3 The recommended specimen is a single-edge b
5、endSE(B) with width, W, equal to twice the specimen thickness,B. An alternate SE(B) specimen with W/B equal to one and aspan, S, to W ratio of 4 may be used but may produce differenttoughness values. A compact tension C(T) specimen may beused if it can be demonstrated that the analysis of resultspro
6、perly accounts for weld-to-base metal strength mismatcheffects on fracture toughness.1.4 The recommended limitation on weld-to-base metalyield strength ratio is0.5,sysweldsysbase, 1.5 (1)Undermatching within this limitation leads to conservativeestimates of fracture toughness, while overmatching may
7、 leadto an overestimation of the fracture toughness by up to 10%.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 appl
8、ica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E8/E8M Test Methods for Tension Testing of MetallicMaterialsE1290 Test Method for Crack-Tip Opening Displacement(CTOD) Fracture Toughness MeasurementE1681 Test Method for Determining Threshold Stress In-tens
9、ity Factor for Environment-Assisted Cracking of Me-tallic MaterialsE1820 Test Method for Measurement of Fracture Tough-nessE1823 Terminology Relating to Fatigue and Fracture Test-ing2.2 ISO Standard:3ISO 12135 Metallic materials Unified method of test forthe determination of quasistatic fracture tou
10、ghnessISO 15653 Metallic materialsMethod of test for the deter-mination of quasistatic fracture toughness of welds3. Terminology3.1 Terminology of E1823 and ISO 15653 are applicable tothis test practice with the following additions.3.2 Definitions:3.2.1 base metal yield strengthThe base metal 0.2% o
11、ffsetyield strength ( sysbase) is defined by testing tensile specimensper Test Method E8/E8M.3.2.1.1 DiscussionISO 15653 uses Rp0,2bto represent thebase metal yield strength.3.2.2 overmatchedAny weldment havingsysweldsysbase. 13.2.3 test temperatureThe test temperature for tensilespecimens shall eit
12、her be identical to the test temperature forthe fracture toughness specimens, or evidence shall be pro-vided to demonstrate that there is not an appreciable change in1This practice is under the jurisdiction of ASTM Committee E08 on Fatigue andFracture and is the direct responsibility of Subcommittee
13、 E08.07 on FractureMechanics.Current edition approved May 1, 2011. Published July 2011. DOI:10.1520E2818-11.2For 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 stan
14、dards Document Summary page onthe ASTM website.3Available from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19
15、428-2959, United States.the yield strength between the test temperature used for thetensile and fracture toughness tests.3.2.4 undermatchedAny weldment havingsysweldsysbase,13.2.5 weld metal yield strengthThe weld metal 0.2%offset yield strength ( sysweld) is defined by testing tensilespecimens per
16、Test Method E8/E8M.3.2.5.1 DiscussionISO 15653 uses Rp0,2wto represent theweld metal yield strength.4. Summary of Practice4.1 This test practice complements ISO 15653 for the qua-sistatic fracture toughness testing of welds. When testingwelds, it is important that the crack tip sample the region and
17、microstructure of interest. Procedures given in ISO 15653 forselecting a specimen orientation, positioning of the fatigueprecrack relative to the weld or heat affected zone (HAZ), andverifying that the resulting measured fracture toughness isrepresentative of the target region or microstructure appl
18、y tothis practice.4.2 This test practice references ISO 15653 for recommen-dations for relieving non-uniform residual stresses ahead ofnotch tips in weld fracture toughness specimens to allow for animprovement in the straightness of fatigue precracks. Wherethermal stress relief treatments are found
19、inadequate, the localcompression technique, which involves indenting the sides ofthe specimens to encompass the notch tip, is the recommendedprocedure.4.3 This practice follows the guidance provided inISO 15653 for relaxation in crack front straightness require-ments provided in the applicable fract
20、ure toughness testmethod; however, this relaxation is valid only for SE(B)specimens evaluated in terms of J or CTOD (not for KIcevaluation).5. Significance and Use5.1 This test practice provides a recommended procedurefor preparing fracture toughness specimens from welds toimprove the likelihood of
21、obtaining useful fracture toughnessvalues.5.1.1 The subsequent fracture toughness values, that havesignificance and use as stated in the applicable ASTM testmethod, may allow for flaw tolerance assessments of weldedstructures. Flaw tolerance assessments require an understand-ing and compensation for
22、 the differences that may existbetween laboratory test results and field conditions.5.1.2 The shallow-notched specimen testing procedures de-scribed in Annex E of ISO 15653 may be used by agreementbetween the parties involved as long as it is understood thatAnnex E is “Informative” and the result is
23、 a geometrydependent measurement of toughness that is not validated bythe applicable test standard.6. Apparatus6.1 The apparatus for specimen preparation and testing is asdescribed in ISO 15653 and the applicable ASTM fracturetoughness test method.7. Specimen Configuration, Dimensions, and Preparati
24、on7.1 The following sections override ISO 15653 where ap-plicable.7.1.1 Specimen:7.1.1.1 Standard ConfigurationA single edge notch bend,SE(B), specimen having a ratio of width W to thickness B(W/B) of two and a span S to W ratio of four is the standardconfiguration.7.1.1.2 Alternative ConfigurationA
25、 specimen havingW/B=1 may also be tested with a S/W=4. However, thisconfiguration may produce different toughness values than thestandard configuration.7.1.1.3 Shallow-crack SE(B) specimen testingWhen themicrostructure of interest in a weld occurs only at a locationwhere the precrack in a SE(B) spec
26、imen must be placed at a/W 0.45, conducting a fracture test will sample the toughness ofthat microstructure; however, it is subject to low constraintconditions that will elevate the measured toughness. If thismicrostructure only occurs at this a/W, then the measuredfracture toughness is representati
27、ve of the weld. On the otherhand, if the microstructure could occur at deep crack locationsin some applications, then the measured fracture toughnesscould be non-conservative. Consequently, the shallow-notchedspecimen testing procedures described in Annex E ofISO 15653 may be used by agreement betwe
28、en the partiesinvolved as long as it is understood that Annex E is “Informa-tive” and the result is a geometry dependent measurement oftoughness.7.1.1.4 Alternative SpecimenThe compact tension, C(T),specimen, which is routinely used to measure fracture tough-ness for base materials, is not recommend
29、ed for fracturetoughness testing of weldments due to a lack of experiencewith both the testing and analysis of welded C(T) specimens.The C(T) specimen may be used if the user demonstrates thatthe equations for interpreting the results appropriately accountfor weld-to-base metal strength mismatch eff
30、ects on fracturetoughness.7.1.1.5 Notch OrientationISO 15653 provides orientationcodes for weld and parent metal specimens. The parent metaldirections designated X, Y, and Z correspond to directions L, Tand S in Test Method E1823.7.2 Pretest Hydrogen Release Heat Treatment:7.2.1 Applicability to Ser
31、vice ConditionsThe presence ofdiffusible hydrogen in a weld can reduce fracture toughness,especially when the rate of straining is low. If the time betweenwelding and testing is shorter than the time between weldingand the structure experiencing its first major loading, it may benecessary to carry o
32、ut hydrogen release heat treatment on thetest weldment. Conversely, when the time between weldingand the structure entering service is short, heat treatment of thewelded test panel for hydrogen release would be inappropriate.7.2.2 Comparability of Multiple Test WeldmentsHeattreatment may also be req
33、uired when it is necessary to comparethe fracture toughness of different weldments and it is notpossible to ensure that the time between welding and testing isthe same. The purpose of the heat treatment is to ensure that theE2818 112level of diffusible hydrogen is the same as that in the structuralw
34、eld, or that consistent hydrogen levels are obtained indifferent panels.7.2.3 Heat Treatment ParametersHydrogen release heattreatment is carried out at approximately 150C (300F), orwithin the range of interpass temperatures for a particularweldment. The time at temperature depends on the thickness o
35、fthe weld and the level of diffusible hydrogen in the weld.4However, if prolonged heat treatment at these temperatures isexpected to influence the fracture toughness by mechanismsother than hydrogen release, then hydrogen release heat treat-ment is not recommended.7.3 Fatigue Precracking:7.3.1 Fatig
36、ue Precracking RequirementsRequirementsconcerning precracking forces, the extent of precrack extensionfrom the machined notch, and the detail of the machined notchshall conform to the applicable ASTM fracture toughness testmethod. All other applicable sections of ISO 15653 apply.7.3.1.1 Thermal Stre
37、ss ReliefPost-weld heat treatment orlocal post-weld heat treatment will relieve, to some extent,residual stresses produced by welding. These thermal stressrelief treatments may be employed prior to fatigue precrackingonly for weldments that will be used in a thermally stressrelieved condition. The t
38、hermal stress relief procedure usedshall be consistent with that employed in service.(1) Demonstration of Precrack Preparation ProcedureEffectivenessIn cases whereAnnex C of ISO 15653 is used tomodify the residual stress field in a specimen, it is advisable tocheck the straightness of the precrack i
39、n the first specimen fora test series from a particular weld to verify the effectiveness ofthe specimen preparation procedure.8. Procedure8.1 Number of SpecimensThe minimum number of validtests conducted shall be 3. Due to the complications associatedwith weldment testing, it may be necessary to tes
40、t from 5 to 6samples to obtain 3 valid results.8.2 Test ProcedureFracture toughness tests shall be con-ducted according to the applicable ASTM test method.9. Post-test Metallography9.1 Post-test metallography sections of ISO 15653 apply.10. Post-test Analysis10.1 The post-test analysis sections of I
41、SO 15653 applywith the provision that all references in ISO 15653 toISO 12135 shall be replaced with the applicable ASTM testmethod, and the following sections override ISO 15653 whereapplicable.10.2 Validity RequirementsAll validity requirements ofthe corresponding ASTM test standard shall apply wi
42、th theexception of the crack front straightness requirement fornon-KIcevaluated SE(B) specimens. In this case, the relaxedcrack front straightness requirement of ISO 15653 applies.11. Report11.1 The report shall include all of the information requiredby the applicable ASTM fracture toughness test st
43、andard usedin conjunction with this test practice.11.1.1 The following information is required in addition tothe information required by ISO 15653.11.2 Additional Information:11.2.1 Notch locationA sketch of the notch location andorientation relative to the etched cross section of the weld shallbe p
44、rovided.11.2.2 Specimen Removal and StraighteningAdescriptionof how the specimen was removed from the original weldment,how much the thickness was reduced (if applicable), and howit was straightened prior to machining (if applicable) shall beincluded.11.2.3 Procedures used to ensure adequate crack f
45、rontstraightnessIndicate the technique used. For thermal stressrelief, document the applied thermal cycle and size of couponwhen stress relieved. For local compression indicate platentype used, platen dimensions, depth of indent and forcerequired to produce the indent. Alternative techniques shallal
46、so be fully documented.11.2.4 Hydrogen RemovalDescribe procedure used forhydrogen release heat treatment, if applicable.11.2.5 Post test metallographyProvide results of metal-lography used to qualify test results.11.2.6 Weld DiscontinuitiesDocument any weld disconti-nuities found on the fracture sur
47、face by post-test examination,and quantify their proximity to the crack tip.11.3 In cases where the weldment has been prepared for theexpress purpose of fracture testing, the following informationshould be noted as part of the test record. If this information isknown for weldments removed from servi
48、ce the informationshould also be recorded, but it is not mandatory.11.3.1 Base metalSpecification, composition, productform and heat treatment.11.3.2 Weld consumableFiller metal specification, heatnumber, flux type and specification, shielding gas.11.3.3 Weld process parametersProcess and position,
49、heatinput, preheat and interpass temperature, weld sequence andnumber of passes.11.3.4 Weld configurationJoint type, set up, and restraint.11.3.5 Weld clean-upBack-gouging of weld root andinter-pass grinding.11.3.6 Postweld heat treatment(PWHT).12. Precision and Bias12.1 PrecisionThe precision statement of the applicablefracture toughness test standard applies.12.2 BiasThe bias statement of the applicable fracturetoughness test standard applies.13. Keywords13.1 fracture toughness; heat affected zone; hydrogen re-lease; overmatched; post-t
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