1、Designation: B645 10Standard Practice forLinear-Elastic PlaneStrain Fracture Toughness Testing ofAluminum Alloys1This standard is issued under the fixed designation B645; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、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 Department of Defense.INTRODUCTIONLinear-elastic plane-strain fracture
3、toughness testing of aluminum alloys is performed essentially inaccordance with Test Method E399. However, there is a need, in the application of Test Method E399for quality assurance testing, to deal with the interpretation of the results for material qualification andrelease in cases where all req
4、uirements for valid measurements of plane-strain fracture toughnesscannot be met. It is the purpose of this practice to provide consistent methods of dealing with thosesituations.1. Scope*1.1 This practice is applicable to the fracture toughnesstesting of all aluminum alloys, tempers, and products,
5、espe-cially in cases where the tests are being made to establishwhether or not individual lots meet the requirements ofspecifications and should be released to customers.1.2 Test Method E399 is the basic test method to be used forplane-strain fracture toughness testing of aluminum alloys. Thepurpose
6、 of this practice is to provide supplementary informa-tion for plane-strain fracture toughness of aluminum alloys inthree main areas:1.2.1 Specimen sampling,1.2.2 Specimen size selection, and1.2.3 Interpretation of invalid test results.1.3 The values stated in SI units are to be regarded asstandard.
7、 No other units of measurement are included in thisstandard.1.3.1 ExceptionCertain inch-pound values given in paren-theses are provided for information only.1.4 This standard is currently written to accommodate onlyC(T) specimens.1.5 This standard does not purport to address all of thesafety concern
8、s, 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:2B646 Practice for Fracture Toughness Testi
9、ng ofAluminumAlloysE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE399 Test Method for Linear-Elastic Plane-Strain FractureToughness KIcof Metallic MaterialsE561 Test Method for K-R Curve DeterminationE1823 Terminology Relating to Fatigue and Fractu
10、re Test-ing3. Terminology3.1 GeneralTerms, definitions, symbols, and orientationdesignations in Test Method E399 and Terminology E1823 areapplicable herein.3.2 The following additional definitions are applicable:3.2.1 invalid plane-strain fracture toughnesstest result,KQ, that does not meet one or m
11、ore of the validity requirementsin Test Method E399 and, where so characterized, is of novalue in judging the true plain-strain fracture toughness of amaterial but may, under certain conditions, adequately guaran-tee the materials fracture toughness for lot release purposes.1This practice is under t
12、he jurisdiction of ASTM Committee B07 on LightMetals and Alloys and is the direct responsibility of Subcommittee B07.05 onTesting.Current edition approved May 1, 2010. Published August 2010. Originallyapproved in 1978. Last previous edition approved in 2007 as B64507. DOI:10.1520/B0645-10.2For refer
13、enced 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.1*A Summary of Changes section appears at the end of this standard.Copy
14、right ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.2 valid plane-strain, fracture toughnesstest resultmeeting all the validity requirements in Test Method E399, thatis, a value of KIc.4. Summary of Practice4.1 This practice supplements T
15、est Method E399 and Prac-tice B646 in three main areas:4.1.1 Specimen sampling,4.1.2 Specimen size selection, and4.1.3 Interpretation of results that fail the validity require-ments in Test Method E399 in one of the following areas inorder to determine if the invalid results are usable for lotreleas
16、e:4.1.3.1 Pmax/PQrequirements,4.1.3.2 Specimen size requirements, and4.1.3.3 Fatigue precracking requirements.5. Significance and Use5.1 This practice for plane-strain fracture toughness testingof aluminum alloys may be used as a supplement to TestMethod E399. The application of this practice is pri
17、marilyintended for quality assurance and material release in caseswhere valid plane-strain fracture toughness data cannot beobtained per Test Method E399.5.2 It must be understood that the interpretations andguidelines in this practice do not alter the validity requirementsof Test Method E399 or pro
18、mote the designation of data thatare invalid according to Test Method E399 to a “valid”condition. This practice is primarily concerned with caseswhere it is not possible or practical to obtain valid data, butwhere material release judgments must be made againstspecified fracture toughness values. Wh
19、ere it is possible toobtain a valid plane-strain fracture toughness value by replace-ment testing according to Test Method E399, that is thepreferred approach.6. Apparatus6.1 All apparatus shall be in conformance with Test MethodE399.7. Sampling7.1 Sampling requirements stated in the individual mate
20、rialspecifications shall be followed. In the absence of specificrequirements in the individual material specifications, speci-mens shall be taken at the following locations:7.1.1 Specimens from plate shall be from the mid-thickness,until the plate thickness is twice the standard specimenthickness fo
21、r that particular product (that is, the specimenthickness selected for lot release and quality assurance testingwhich typically yields a valid KIcfor that particular alloy andproduct), at and beyond which the specimen shall be centeredat the quarter-thickness location.7.1.2 Specimens from forgings,
22、extrusions, and rod shall betaken from the center of the cross section as far as is practical.NOTE 1Considerable care should be taken in specifying the locationof specimens within the thickness of the thick plate, forgings, extrusions,or rod because fracture toughness may vary appreciably with locat
23、ionthrough the thickness.8. Test Specimen Configuration and Dimensions8.1 Specimen size requirements stated in the individualmaterial specifications shall be followed. In the absence ofspecific requirements, the specimen types, general configura-tion, and size requirements in Test Method E399 are ap
24、plicableherein with the following supplemental recommendations andrequirements:8.1.1 For aluminum products, the recommended minimumspecimen ligament length is:W a! $5SKQsYSD2(1)rather than the required minimum of:W a! $2.5SKQsYSD2(2)in Test Method E399.NOTE 2Experimental studies3have shown that more
25、 uniform valuesof KQare obtained for high toughness aluminum alloys when theconditions of Eq 1 are met.8.1.2 In all cases, the specimen W/B ratio shall be greaterthan or equal to 2 and less than or equal to 4 based on nominalspecimen dimensions. Other specimen dimensional propor-tions in Test Method
26、 E399 shall also be maintained.NOTE 3Specimens meeting this requirement correspond to the stan-dard (W/B = 2) or alternative specimen geometries (2# W/B #4) in TestMethod E399.8.1.3 When the minimum size requirement of:W a! $2.5SKQsYSD2in Test Method E399 cannot be met due to product dimensionalcons
27、traints, the specimen shall be machined such that the Wdimension is maximized to the nearest 12.7 mm (0.5 in.) at thespecified test location while still meeting the requirements of8.1.2 up to the specimen width required in the applicablematerial specification, or if no width is specified, up to an u
28、pperrequired limit of 127 mm (5.0 in.).NOTE 4It is not practical for W to vary continuously (that is,non-discretely) since many C(T) specimen dimensions are proportional toW. Each change in W requires a different machining or testing setup.Therefore, it is required that W be maximized to the nearest
29、 12.7 mm (0.5in.).8.1.4 When the requirement Pmax/PQ# 1.1 cannot be metdue to product dimensional constraints, the specimen shall bemachined such that the B dimension is maximized up to arequired maximum thickness of 63.5 mm (2.5 in.) at thespecified test location. The specimen ligament length shoul
30、d bemaintained at:W a! $2.5SKQsYSD2(3)or as large as possible while still meeting the requirements of8.1.2, up to the specimen width required in the applicablematerial specification, or if no width is specified, up to an upper3Kaufman, J. G., “Experience in Plane Strain Fracture Toughness per ASTME3
31、99,” Developments in Fracture Mechanics Test Methods Standardization, ASTMSTP 632, ASTM, 1977, pp. 3-24.B645 102required limit of 127 mm (5.0 in.).NOTE 5The upper limit on specimen thickness and width have beenestablished because of practical limitations on how large a specimen canbe routinely machi
32、ned and tested for lot release purposes in a productionenvironment using standard equipment. The producer may test thickerand/or wider specimens provided the testing capability and sufficientmaterial are available, and the specimen proportions adhere to therequirements in 8.1.2.8.1.5 When it is not
33、possible to meet either the:W a! $2.5SKQsYSD2(4)or the:PmaxPQ#1.1 (5)requirements, then both the W and B dimensions shall bemaximized in accordance with requirements in 8.1.2, 8.1.3, and8.1.4.NOTE 6For aluminum products where the size requirement in eitherEqs 4 or 5 cannot be consistently met becaus
34、e of high toughness, evenwhen B and W are maximized, other measures of fracture toughness suchas KR25described in Practice B646 or the K-R curve as described in TestMethod E561 should be considered for evaluating fracture toughness forlot release purposes.NOTE 7Test Method E399 permits the use of si
35、de-grooved specimensin certain specimen types. Side-grooved specimens may allow for validKICvalues to be obtained for high toughness alloys or thin products thatotherwise would have invalidities due to excessive plasticity. For lotacceptance testing, side-grooved specimens shall not be used unlesssp
36、ecifically allowed by the product specification or by agreement betweenproducer and user. Side-grooves increase the level of constraint withrespect to the recommended specimen. The increased constraint promotesa more uniform stress state along the crack front and inhibits shear lipdevelopment.As a r
37、esult, a KICvalue obtained from testing a side-groovedspecimen is expected to be lower than a KICvalue obtained from testingthe recommended specimen, particularly for thin products or tests exhib-iting Type I behavior. For use of side-grooves in lot acceptance testing,minimum KICvalues specific to s
38、ide-grooved specimens may need to beestablished.9. Fatigue Precracking9.1 Fatigue precracking shall be performed and fatiguecrack front measurements shall be made in accordance withTest Method E399.10. Procedure10.1 The test procedure, analysis of test record, and calcu-lations shall be made in acco
39、rdance with Test Method E399.11. Interpretation of Results11.1 AKQvalue that satisfies all of the validity requirementsof Test Method E399 is a valid KICin accordance with thispractice. A KQvalue that does not meet all of the requirementsof Test Method E399 is not a valid KICvalue in accordancewith
40、Test Method E399 or this practice, but is usable for lotrelease purposes if all of the appropriate requirements in thissection are met.11.2 AKQvalue that has invalidities in accordance with TestMethod E399, but which meets the specimen width andthickness requirements in the individual material speci
41、fication,is usable for lot release provided the secondary conditions in11.5 and 11.6 are met.11.3 In the absence of specific requirements in the indi-vidual material specification, a KQvalue having invalidities inaccordance with Test Method E399 is usable for lot releaseprovided that each invalidity
42、 meets all of the secondaryconditions in 11.4, 11.5, and 11.6.11.4 Invalidities Related to Specimen Size and Pmax/PQRequirements:11.4.1 In all cases, the specimen W/B ratio must meet therequirements in 8.1.2. Otherwise, a replacement test shall beperformed using a specimen meeting those requirements
43、.11.4.2 If a KQvalue is invalid because the specimen doesnot meet the:W a! $2.5SKQsYSD2requirement but the test record meets the:PmaxPQ#1.1requirement, the KQvalue may be usable for lot release if thespecimen width W is maximized according to 8.1.3.11.4.3 If a KQvalue is invalid because the test rec
44、ord doesnot meet the:PmaxPQ#1.1requirement but the specimen size does meet the:W a! $2.5SKQsYSD2requirement, the KQvalue may be usable for lot release if thethickness is maximized according to 8.1.4.11.4.4 If a KQvalue is invalid because it fails to meet boththe:PmaxPQ#1.1 (6)requirement and the:W a
45、! $2.5SKQsYSD2(7)requirement, the KQvalue may be usable for lot release if thewidth W and the thickness B are maximized according to 8.1.5.NOTE 8Under the conditions in 11.4.2, 11.4.3, and 11.4.4, the KQvalue may not represent or approximate KIc, but it does represent ameasure of the materials resis
46、tance to fracture. KQvalues obtained underthese conditions may also depend significantly on the specimen geometryand dimensions. Therefore, both the specified value and the qualificationtesting should be based on a specimen of the same geometry anddimensions.11.5 Invalidities Related to Fatigue Prec
47、racking:11.5.1 If the maximum stress intensity in the final stage ofprecracking (Kfmax) exceeds the limit of 60% of KQallowed inTest Method E399, but still satisfies the requirement that:KfmaxE#0.00032 m0.002 in.!,the KQvalue may be usable for lot release if Kfmaxis no moreB645 103than 80% of KQ. Ot
48、herwise, a replacement test shall beperformed.11.5.2 If the crack length a determined in accordance withTest Method E399 is outside the range allowed in E399 (0.45Wto 0.55W), the KQvalue may be usable for lot release if thecrack length a is within the range 0.4W to 0.6W. Otherwise, areplacement test
49、 shall be performed.11.6 Other Invalidities: To be usable for lot release, a KQvalue must also satisfy all other validity requirements in TestMethod E399 not covered in 11.4 and 11.5. Otherwise, areplacement test shall be performed.11.7 Annex A1 provides a flowchart to help the userunderstand how to interpret an invalid KQvalue from E399 todetermine if it is usable for lot release according to thisPractice.12. Report12.1 The record shall include all information required byTest Method E399 and individual reasons for invalid resultsbe
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