1、Designation: E 2248 09Standard Test Method forImpact Testing of Miniaturized Charpy V-Notch Specimens1This standard is issued under the fixed designation E 2248; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi
2、sion. 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 test method describes notched-bar impact testing ofmetallic materials using Miniaturized Charpy V-Notch(MCVN) specimens an
3、d 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 standard concerns Miniaturized Charpy V-Notc
4、hspecimens, for which all linear dimensions, including lengthand notch depth, are reduced with respect to a type A standardimpact test specimen in accordance with Test Methods E23.These are not the same as sub-size specimens, described inAnnex A3 of Test Methods E23, for which length, notch angleand
5、 notch depth are the same as for the standard typeACharpyspecimen. See also 1.5 below.1.3 Comparison of the MCVN data with conventionalCharpy V-Notch (CVN) data or application of the MCVN data,or both, to the evaluation of ferritic material behavior is theresponsibility of the user of this test meth
6、od and is notexplicitly covered 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 standard does not address testing of sub-sizespecimens as discussed in Test Methods E23. The readershould understan
7、d 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 ofconventional Test
8、 Methods E23specimens.1.6 The MCVN test may be performed using a typical TestMethods E23test 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 is therespons
9、ibility 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:2A 370 Test Methods and Definitions for Mechanical Testingof Steel ProductsE23 Test Methods for
10、 Notched Bar Impact Testing ofMetallic MaterialsE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 2298 Test Method for Instrumented Impact Testing ofMetallic Materials2.2 ISO St
11、andards:3ISO 148 Metallic materials - Charpy pendulum impact test- Part 1: Test methodISO 14556 Steel - Charpy V-notch pendulum impact test -Instrumented test method3. Summary of Test Method3.1 The essential features of the MCVN impact test are: (a)a suitable miniature three point bend specimen, (b)
12、 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) a device fordetermining the energy absorbed by the broken specimen
13、, andoptionally (e) instrumentation for measuring applied force as afunction of time during specimen loading (refer to MethodE 2298).3.2 The test consists of breaking the miniaturized specimen,notched in the middle, and supported at each end, with oneblow from a swinging pendulum under conditions de
14、finedhereafter.4. Significance and Use4.1 There are cases where it is impractical or impossible toprepare conventional CVN specimens. MCVN specimens are1This test method is under the jurisdiction of ASTM Committee E28 onMechanical Testing and is the direct responsibility of Subcommittee E28.07 onImp
15、act Testing.Current edition approved April 1, 2009. Published April 2009.2For 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 standards Document Summary page onthe A
16、STM website.3Available from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.an alterna
17、tive approach for characterizing notched specimenimpact behavior. Typical applications include MCVN speci-mens prepared from the broken halves of previously testedspecimens, from thin product form material, or from materialcut from in-service components.4.2 This standard establishes the requirements
18、 for perform-ing impact tests on MCVN specimens fabricated from metallicmaterials. Minimum requirements are given for measurementand recording equipment such that similar sensitivity andcomparable measurements, as compared to conventional CVNtests, are achieved. The user should be aware that the tra
19、nsitionregion temperature dependence data obtained from MCVNspecimens are not directly comparable to those obtained fromfull-size standard Charpy-V specimens and suitable correlationprocedures have to be employed to obtain ductile-to-brittletransition temperature (DBTT) data equivalent to those ob-t
20、ained using CVN specimens. In all instances, correlations willhave to be developed to relate upper shelf energy (USE) datafrom MCVN test to CVN comparable energy levels. Applica-tion of MCVN test data to the evaluation of ferritic materialbehavior is the responsibility of the user of this test metho
21、d.MCVN test data should not be used directly to determine thelowest allowable operating temperature for an in-service ma-terial. The data must be interpreted within the framework of afracture mechanics assessment.4.3 While this Test Method treats the use of an instrumentedstriker as an option, the u
22、se of instrumentation in the impacttest is recommended and is fully described in Test MethodE 2298. In 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-displacem
23、ent curve is a measure of absorbed energy.As an alternative, absorbed energy may be evaluated directlyfrom machine dial reading. Whenever possible, an opticalencoder shall be used in place of the machine dial because anencoder has better resolution than a dial.5. Test Machine5.1 The test shall be ca
24、rried out with a pendulum-typeimpact testing machine which is (optionally) instrumented todetermine force-time 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 energy measurements can be o
25、btained with a resolu-tion better than or equal to 0.1 J, the same test machine used forCVN testing may be used to test MCVN specimens.5.2 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
26、 for CVNtesting is used for MCVN specimens, refer to Appendix X3 ofE23for changing the specimen support height by manufactur-ing new supports or adding shims.5.3 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 1I
27、mpact velocities above 4 m/s are not advisable for instru-mented MCVN tests, since excessive oscillations 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 instrumen
28、ted curve), lower velocities are allowed forMCVN tests than required by E23(not less than 3 m/s).5.4 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 tha
29、t is proportional to the CVN specimen. Fig. 1shows the dimensions of 8 and 2 mm strikers (3.86 mm 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. ForFIG. 1 Scaled 8 mm and 2 mm Strikers for Use in Miniaturized Charpy Impact TestE2248092bot
30、h of these scaled strikers, the anvil radius is scaled to 0.486 0.025 mm, and the span is 19.3 6 0.025 mm.5.5 A non-scaled 2 mm striker can be used to test the 4 by3 by 27 mm MCVN specimen described in Annex D of ISO14556. The anvil radius and span, in this case are 10+0.50mmand 220+0.10mm respectiv
31、ely.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, so scaling is not appropriate.5.6 The testing machine shall be a pendulum type of rigidconstruction. All general requir
32、ements for apparatus and cali-bration specified in Test Methods E23shall be satisfied.5.7 For instrumented force measurements using optionalforce measuring instrumentation, the requirements given inTest Method E 2298 regarding striker instrumentation, dataacquisition, and data analysis shall be sati
33、sfied.6. Hazards6.1 Safety precautions should be taken to protect personnelfrom electric shock, the swinging pendulum, flying brokenspecimens, and hazards associated with specimen warming andcooling media. See also 1.6.7. Test Specimens7.1 The recommended proportional specimen configurationis the sq
34、uare cross section notched bar shown in Fig. 2. Thecross sectional dimension is slightly under 5 mm to enablemachining from a previously tested CVN. Information onadditional specimen geometries that have been successfullyused is provided in Appendix X1.NOTE 3In case MCVN specimens are extracted from
35、 broken CVNspecimens of highly ductile materials, the user should ensure that thesevere plastic deformation occurred during fracture of the CVN specimensdoes not affect the impact behavior of the miniaturized samples.7.2 Microstructural considerations dictate that only V-notchspecimens with cross se
36、ctional dimensions sufficient to ensurea representative volume of material is tested may be used. Inorder to satisfy this requirement, the size scale and meanseparation distance of inhomogeneities that exist in the mate-rial must be known. The cross sectional dimension must be atleast five times gre
37、ater than the largest inhomogeneity. Post-test metallography may be performed in order to confirm thatthe requirement has been met.7.3 Stress field similitude dictates that if the miniaturizedspecimens (such as the one shown in Fig. 2) do not satisfy themicrostructural considerations, specimens with
38、 a larger crosssection may be used. For the square cross section specimen inFig. 2, all the remaining specimen dimensions (length, notchdepth, etc.) shall be scaled by appropriate ratio with theconventional CVN dimensions. This has the advantage ofstandardization of approach and scalability of previ
39、ouslycalculated finite element solutions.7.4 Side grooving of the MCVN specimens (see also Ap-pendix X2) is optional. Investigations (1) have shown that theuse of side grooves on MCVN specimens provides a largervolume of material which is sampled at plane strain conditions.This results in less downw
40、ard shift in temperature due to lossof constraint caused by miniaturization, and thereby reducesthe need for correction factors to simulate CVN transitionalfracture temperature dependence.7.5 The choice of specimen depends on the application.NOTE 4Although this test method specifically addresses imp
41、act testsperformed on notched specimens, the use of unnotched samples may beadvantageous when testing refractory metals or materials produced bypowder metallurgy methods. For such materials, machining an accurateNOTE 1The notch root radius shall be 0.13 mm.NOTE 2Permissible variations shall be as fo
42、llows:notch length to edge 90 6 2radius of notch 60.025 mmadjacent sides at 90 6 10 minnotch depth 60.025 mmcross section dimensions 60.025 mmfinish requirements 2 im notched surface/opposite4 im other surfaceslength of specimen +0, 0.12 mmcentering of notch 60.12 mmangle of notch 61FIG. 2 Miniaturi
43、zed Charpy Impact SpecimenE2248093notch without producing significant damage is extremely difficult. The useof unnotched specimens, however, is outside the scope of this test method.8. Test Procedure8.1 The test procedure may be summarized as follows: thetest specimen is heated/cooled in situ (that
44、is, at the impactlocation) or it is removed from its cooling (or heating) medium,and positioned on the specimen supports; the pendulum isreleased with minimum vibration; and the absorbed energy isrecorded from the machine dial or, preferably, from the opticalencoder. For instrumented tests, the forc
45、e-time curve is mea-sured and evaluated to give the total absorbed energy.8.2 The temperature of the specimen at impact must bewithin 62C of the nominal test temperature. Due to the smallsize of the specimen, in tests below or above room temperature(RT), special attention must be devoted to temperat
46、ure controlwithin the above mentioned tolerance. It is recommended thatin-situ heating/cooling be used. If a bath transfer system isused, it will be necessary to transfer the specimen to thesupports and strike the specimen within a very short period oftime (1sorless). If a thermal bath transfer syst
47、em is notused, dummy specimens (with internal thermocouples) or testspecimens (with surface thermocouples) shall be used todemonstrate that the 62C requirement has been met. If in-situheating/cooling is used, dummy specimens (with internalthermocouples) or test specimens (with surface thermocouples)
48、shall be used to calibrate the system and to demonstrate that the62C requirement has been met.8.3 The specimen shall be placed on the supports against theanvils to ensure that the notch is centered to within 0.25 mm.9. Lateral Expansion and Percent Shear Determination9.1 The measurement of lateral e
49、xpansion shall satisfy therequirements of Test Methods E23. The uncertainty of themeasurement shall be determined by using precision machinedreference blocks.9.2 The fracture appearance, characterized as percent sheararea, may be measured directly or determined using a correla-tion of characteristic values (see 9.2.2).9.2.1 Direct measurement of fracture appearance shall sat-isfy the requirements of Test Methods E23.9.2.2 Fracture Appearance CorrelationThe equations de-scribed in Method E 2298 may be used to estimate the shearfracture area. These equations rela
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1