1、Designation: E2248 18Standard Test Method forImpact Testing of Miniaturized Charpy V-notch Specimens1This standard is issued under the fixed designation E2248; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method describes notched-bar impact testing ofmetallic materials using Miniaturized Charpy V-notch(MCVN) specimens and
3、 test apparatus. It provides: (a)adescription of the apparatus, (b) requirements for inspectionand calibration, (c) safety precautions, (d) sampling, (e) dimen-sions and preparation of specimens, (f) testing procedures, and(g) precision and bias.1.2 This test method concerns Miniaturized Charpy V-no
4、tchspecimens, for which all linear dimensions, including lengthand notch depth, are reduced with respect to a standard CharpyV-notch impact test specimen in accordance with Test MethodsE23. These are not the same as sub-size specimens, describedin Annex A3 of Test Methods E23, for which length, notc
5、hangle and notch depth are the same as for the standard CharpyV-notch specimen. See also 1.5 below.1.3 Comparison of the MCVN data with standard CharpyV-notch (CVN) data or application of the MCVN data, or both,to the evaluation of ferritic material behavior is the responsi-bility of the user of thi
6、s test method and is not explicitlycovered by this test method.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This test method does not address testing of sub-sizespecimens as discussed in Test Methods E23. The readersh
7、ould understand the distinction between miniature and sub-size. Miniature specimens are shorter that sub-size specimensso that more tests can be conducted per unit volume ofmaterial. Moreover, miniature specimens are designed so thatthe stress fields which control fracture are similar to those ofsta
8、ndard Test Methods E23 specimens.1.6 The MCVN test may be performed using a typical TestMethods E23 test machine with suitably modified anvils andstriker or using a smaller capacity machine.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It i
9、s 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.1.8 This international standard was developed in accor-dance with internationally recognized principles on st
10、andard-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:2E23 Test Methods for Notched Bar Impact Tes
11、ting of Me-tallic MaterialsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE2298 Test Method for Instrumented Impact Testing ofMetallic Materials2.2 ISO Standards:3ISO 14556 Steel
12、 - Charpy V-notch pendulum impact test -Instrumented test method3. Terminology3.1 Definitions of terms Common to Mechanical Testing:3.1.1 absorbed energy FL, nwork spent to fracture aspecimen in a single pendulum swing, as measured by acompensated indicating device3.1.2 instrumented absorbed energy,
13、 WtFL, nwork spentto fracture a specimen in a single pendulum swing, as calcu-lated by integrating the force-displacement curve.3.1.3 lateral expansion L, nthe maximum increase inthickness of the specimen as a result of the impact test,expressed in mm.1This test method is under the jurisdiction of A
14、STM Committee E28 onMechanical Testing and is the direct responsibility of Subcommittee E28.07 onImpact Testing.Current edition approved June 1, 2018. Published September 2018. Originallyapproved in 2009. Last previous edition approved in 2015 as E224815. DOI:10.1520/E2248-18.2For referenced ASTM st
15、andards, 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.3Available from International Organization for Standardization (ISO), 1, ch. dela Vo
16、ie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed i
17、n accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.1.3.1 Discussionlateral
18、 expansion is used as a measureof ductility.3.1.4 shear fracture appearance, SFA, nthe amount offracture surface in the specimen that failed in a shear (stable)mode, expressed in percent.4. Summary of Test Method4.1 The essential features of the MCVN impact test are: (a)a suitable miniature three po
19、int bend specimen, (b) anvils andsupports on which the test specimen is placed to receive theblow of the moving mass, (c) a moving mass (striker) that hasbeen released from a sufficient height to cause the mass tobreak the specimen placed in its path, (d) an indicating devicefor determining the abso
20、rbed energy of the broken specimen,and optionally (e) instrumentation for measuring applied forceas a function of time during specimen loading (refer to TestMethod E2298).4.2 The test consists of breaking the miniaturized specimen,notched in the middle, and supported at each end, with oneblow from a
21、 swinging pendulum under conditions definedhereafter.5. Significance and Use5.1 There are cases where it is impractical or impossible toprepare standard CVN specimens. MCVN specimens are analternative approach for characterizing notched specimen im-pact behavior. Typical applications include MCVN sp
22、ecimensprepared from the broken halves of previously testedspecimens, from thin product form material, or from materialcut from in-service components.5.2 This test method establishes the requirements for per-forming impact tests on MCVN specimens fabricated frommetallic materials. Minimum requiremen
23、ts are given for mea-surement and recording equipment such that similar sensitivityand comparable measurements, as compared to standard CVNtests, are achieved. The user should be aware that the transitionregion temperature dependence data obtained from MCVNspecimens are not directly comparable to th
24、ose obtained fromfull-size standard Charpy V-notch specimens and suitablecorrelation procedures have to be employed to obtain ductile-to-brittle transition temperature (DBTT) data equivalent tothose obtained using CVN specimens. In all instances, corre-lations will have to be developed to relate upp
25、er shelf energy(USE) data from MCVN test to CVN comparable energylevels. Application of MCVN test data to the evaluation offerritic material behavior is the responsibility of the user of thistest method. MCVN test data should not be used directly todetermine the lowest allowable operating temperatur
26、e for anin-service material. The data must be interpreted within theframework of a fracture mechanics assessment.5.3 While this test method treats the use of an instrumentedstriker as an option, the use of instrumentation in the impacttest is recommended and is fully described in Test MethodE2298. I
27、n order to establish the force-displacement diagram, itis necessary to measure the impact force as a function of timeduring contact of the striker with the specimen. The area underthe force-displacement curve is a measure of instrumentedabsorbed energy. Absorbed energy may be evaluated directlyfrom
28、machine dial reading. Whenever possible, an opticalencoder shall be used in place of the machine dial because anencoder has better resolution than a dial.6. Test Machine6.1 The test shall be carried out with a pendulum-typeimpact testing machine which is (optionally) instrumented todetermine force-t
29、ime curves. The test machine shall havesufficient capacity to break the specimen in one blow whilelosing not more than 80 % of the initial potential energy.Provided absorbed energy measurements can be obtained witha resolution better than or equal to 0.1 J, the same test machineused for CVN testing
30、may be used to test MCVN specimens.6.2 The MCVN specimen has to be suitably supported sothat the centerline of the specimen coincides with the center ofstrike of the pendulum. If the same machine used for CVNtesting is used for MCVN specimens, refer to Appendix X3 ofE23 for changing the specimen sup
31、port height by manufactur-ing new supports or adding shims.6.3 The impact velocity (tangential velocity) of the pendu-lum at the center of the strike shall not be less than 1 nor morethan 6 m/s.NOTE 1Impact velocities above 4 m/s are not advisable for instru-mented MCVN tests, since excessive oscill
32、ations are then superimposedon the initial portion of the test diagram and errors in the evaluation of theforce-displacement trace may occur. For the same reason (ease ofinterpretation of the instrumented curve), lower velocities are allowed forMCVN tests than required by E23 (not less than 3 m/s).6
33、.4 It is recommended that the scalability of the stress fieldsis maintained. This is accomplished by scaling the strikerradius, anvil radii, and the span of the anvils with respect to aspecimen size that is proportional to the CVN specimen. Fig. 1shows the dimensions of 8 and 2 mm strikers (3.86 mm
34、and0.96 mm) scaled for use with the nominal12-scale MCVN(4.83 by 4.83 by 24.13 mm) specimen shown in Fig. 2. Forboth of these scaled strikers, the anvil radius is scaled to 0.48mm 6 0.025 mm, and the span is 19.3 mm 6 0.025 mm.6.5 A non-scaled 2 mm striker can be used to test the 4 by3 by 27 mm MCVN
35、 specimen described in Annex D of ISO14556. The anvil radius and span, in this case are 10+0.50mmand 220+0.10mm respectively.NOTE 2This particular test is allowed because a substantial amount ofdata exists for this specimen and test geometry. This MCVN specimen isnot proportional to the CVN specimen
36、, so scaling is not appropriate.6.6 The testing machine shall be a pendulum type of rigidconstruction. All general requirements for apparatus and cali-bration specified in Test Methods E23 shall be satisfied.6.7 For instrumented force measurements using optionalforce measuring instrumentation, the r
37、equirements given inTest Method E2298 regarding striker instrumentation, dataacquisition, and data analysis shall be satisfied.7. Hazards7.1 Safety precautions should be taken to protect personnelfrom electric shock, the swinging pendulum, flying brokenE2248 182specimens, and hazards associated with
38、 specimen warming andcooling media. See also 1.6.8. Test Specimens8.1 The recommended proportional specimen configurationis the square cross section notched bar shown in Fig. 2. Thecross sectional dimension is slightly under 5 mm to enablemachining from a previously tested CVN. Information onadditio
39、nal specimen geometries that have been successfullyused is provided in Appendix X1.NOTE 3In case MCVN specimens are extracted from broken CVNspecimens of highly ductile materials, the user should ensure that thesevere plastic deformation occurred during fracture of the CVN specimensdoes not affect t
40、he impact behavior of the miniaturized samples.8.2 Microstructural considerations dictate that only V-notchspecimens with cross sectional dimensions sufficient to ensurea representative volume of material is tested may be used. Inorder to satisfy this requirement, the size scale and meanseparation d
41、istance of inhomogeneities that exist in the mate-rial must be known. The cross sectional dimension must be atFIG. 1 Scaled 8 mm and 2 mm Strikers for Use in Miniaturized Charpy Impact TestingNOTE 1Permissible variations shall be as follows:Angle of striker 1Radius of curvature of striking edgeNomin
42、al 1 mm Striker: +0.25, 0 mmNominal 4 mm Striker: 0.025 mmRadius of shoulder of nominal 4 mm striker 0.025 mmWidth of edge of nominal 4 mm striker 0.025 mmSurface finish requirements 0.1m or betterNotch length to edge 90 2Notch root radius 0.025 mmAdjacent sides at 9010minLigament length 0.025 mmCro
43、ss section dimensions 0.025 mmFinish requirements2m notched surface/opposite surface4m other surfacesLength of specimen +0, -0.12mmCentering of notch 0.12 mmAngle of notch 1FIG. 2 Nominal12-Scale Miniaturized Charpy Impact SpecimenE2248 183least five times greater than the largest inhomogeneity. Pos
44、t-test metallography may be performed in order to confirm thatthe requirement has been met.8.3 Stress field similitude dictates that if the miniaturizedspecimens (such as the one shown in Fig. 2) do not satisfy themicrostructural considerations, specimens with a larger crosssection may be used. For
45、the square cross section specimen inFig. 2, all the remaining specimen dimensions (length, notchdepth, etc.) shall be scaled by appropriate ratio with thestandard CVN dimensions. This has the advantage of standard-ization of approach and scalability of previously calculatedfinite element solutions.8
46、.4 Machining the outside surfaces of the MCVN specimensusing continuous wire electric discharge machining (EDM) orany other machining method which produces less than 0.005mm of disturbed material on the surface is acceptable (1). Thecrack starter notch shall be EDM machined or precisionground.8.5 Si
47、de grooving of the MCVN specimens (see also Ap-pendix X2) is optional. Investigations (see Appendix X2) haveshown that the use of side grooves on MCVN specimensprovides a larger volume of material which is sampled at planestrain conditions. This results in less downward shift intemperature due to lo
48、ss of constraint caused by miniaturization,and thereby reduces the need for correction factors to simulateCVN transitional fracture temperature dependence.8.6 The choice of specimen depends on the application.NOTE 4Although this test method specifically addresses impact testsperformed on notched spe
49、cimens, the use of unnotched samples may beadvantageous when testing refractory metals or materials produced bypowder metallurgy methods. For such materials, machining an accuratenotch without producing significant damage is extremely difficult. The useof unnotched specimens, however, is outside the scope of this test method.8.6.1 For some materials, the use of different methods formachining specimens may increase results variability and datascatter. For this reason, the machining method used shall bereported (see 12.1.2). Performing mic
