1、Designation: E2248 12E2248 13Standard 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 las
2、t revision. 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 of metallic materials using Miniaturized Charpy V-Notch (MCVN)speci
3、mens and test apparatus. It provides: (a) a description of the apparatus, (b) requirements for inspection and calibration, (c)safety precautions, (d) sampling, (e) dimensions and preparation of specimens, (f) testing procedures, and (g) precision and bias.1.2 This standard concerns Miniaturized Char
4、py V-Notch specimens, for which all linear dimensions, including length andnotch depth, are reduced with respect to a type A standard impact test specimen in accordance with Test Methods E23. These arenot the same as sub-size specimens, described in Annex A3 of Test Methods E23, for which length, no
5、tch angle and notch depthare the same as for the standard type A Charpy specimen. See also 1.5 below.1.3 Comparison of the MCVN data with conventional Charpy V-Notch (CVN) data or application of the MCVN data, or both,to the evaluation of ferritic material behavior is the responsibility of the user
6、of this test method and is not explicitly covered bythis test method.1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.5 This standard does not address testing of sub-size specimens as discussed in Test Methods E23. The re
7、ader shouldunderstand the distinction between miniature and subsize. Miniature specimens are shorter that sub-size specimens so that moretests can be conducted per unit volume of material. Moreover, miniature specimens are designed so that the stress fields whichcontrol fracture are similar to those
8、 of conventional Test Methods E23 specimens.1.6 The MCVN test may be performed using a typical Test Methods E23 test machine with suitably modified anvils and strikeror using a smaller capacity machine.1.7 This standard does not purport to address all of the safety concerns, if any, associated with
9、its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A370 Test Methods and Definitions for Mechanical Testing of Steel Produc
10、tsE23 Test Methods for Notched Bar Impact Testing of Metallic MaterialsE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodE2298 Test Method for Instrumented Impact Testing of Metal
11、lic Materials2.2 ISO Standards: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 thre
12、e point bend specimen, (b) anvils andsupports on which the test specimen is placed to receive the blow of the moving mass, (c) a moving mass (striker) that has been1 This test method is under the jurisdiction of ASTM Committee E28 on Mechanical Testing and is the direct responsibility of Subcommitte
13、e E28.07 on Impact Testing.Current edition approved April 1, 2012April 1, 2013. Published May 2012April 2013. Originally approved in 2009. Last previous edition approved in 20092012 asE224809.12. DOI: 10.1520/E2248-12.10.1520/E2248-13.2 For referencedASTM standards, visit theASTM website, www.astm.o
14、rg, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Gen
15、eva 20, Switzerland, http:/www.iso.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM
16、recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1released
17、from a sufficient height to cause the mass to break the specimen placed in its path, (d) a device for determining the energyabsorbed by the broken specimen, and optionally (e) instrumentation for measuring applied force as a function of time duringspecimen loading (refer to Test Method E2298).3.2 Th
18、e test consists of breaking the miniaturized specimen, notched in the middle, and supported at each end, with one blowfrom a swinging pendulum under conditions defined hereafter.4. Significance and Use4.1 There are cases where it is impractical or impossible to prepare conventional CVN specimens. MC
19、VN specimens are analternative approach for characterizing notched specimen impact behavior. Typical applications include MCVN specimensprepared from the broken halves of previously tested specimens, from thin product form material, or from material cut fromin-service components.4.2 This standard es
20、tablishes the requirements for performing impact tests on MCVN specimens fabricated from metallicmaterials. Minimum requirements are given for measurement and recording equipment such that similar sensitivity and comparablemeasurements, as compared to conventional CVN tests, are achieved. The user s
21、hould be aware that the transition regiontemperature dependence data obtained from MCVN specimens are not directly comparable to those obtained from full-sizestandard Charpy-V specimens and suitable correlation procedures have to be employed to obtain ductile-to-brittle transitiontemperature (DBTT)
22、data equivalent to those obtained using CVN specimens. In all instances, correlations will have to bedeveloped to relate upper shelf energy (USE) data from MCVN test to CVN comparable energy levels.Application of MCVN testdata to the evaluation of ferritic material behavior is the responsibility of
23、the user of this test method. MCVN test data should notbe used directly to determine the lowest allowable operating temperature for an in-service material. The data must be interpretedwithin the framework of a fracture mechanics assessment.4.3 While this Test Methodtest method treats the use of an i
24、nstrumented striker as an option, the use of instrumentation in theimpact test is recommended and is fully described in Test Method E2298. In order to establish the force-displacement diagram,it is necessary to measure the impact force as a function of time during contact of the striker with the spe
25、cimen. The area underthe force-displacement curve is a measure of absorbed energy. As an alternative, absorbed energy may be evaluated directly frommachine dial reading. Whenever possible, an optical encoder shall be used in place of the machine dial because an encoder hasbetter resolution than a di
26、al.5. Test Machine5.1 The test shall be carried out with a pendulum-type impact testing machine which is (optionally) instrumented to determineforce-time curves. The test machine shall have sufficient capacity to break the specimen in one blow while losing not more than80 % of the initial potential
27、energy. Provided energy measurements can be obtained with a resolution better than or equal to 0.1J, the same test machine used for CVN testing may be used to test MCVN specimens.5.2 The MCVN specimen has to be suitably supported so that the centerline of the specimen coincides with the center of st
28、rikeof the pendulum. If the same machine used for CVN testing is used for MCVN specimens, refer to Appendix X3 of E23 forchanging the specimen support height by manufacturing new supports or adding shims.5.3 The impact velocity (tangential velocity) of the pendulum at the center of the strike shall
29、not be less than 1 nor more than6 m/s.NOTE 1Impact velocities above 4 m/s are not advisable for instrumented MCVN tests, since excessive oscillations are then superimposed on the initialportion of the test diagram and errors in the evaluation of the force-displacement trace may occur. For the same r
30、eason (ease of interpretation of theinstrumented curve), lower velocities are allowed for MCVN tests than required by E23 (not less than 3 m/s).5.4 It is recommended that the scalability of the stress fields is maintained. This is accomplished by scaling the striker radius,anvil radii, and the span
31、of the anvils with respect to a specimen size that is proportional to the CVN specimen. Fig. 1 shows thedimensions of 8 and 2 mm strikers (3.86 mm and 0.96 mm) scaled for use with the nominal 12-scale MCVN (4.83 by 4.83 by 24.13mm) specimen shown in Fig. 2. For both of these scaled strikers, the anv
32、il radius is scaled to 0.48 mm 6 0.025 mm, and the spanis 19.3 mm 6 0.025 mm.5.5 A non-scaled 2 mm striker can be used to test the 4 by 3 by 27 mm MCVN specimen described in Annex D of ISO 14556.The anvil radius and span, in this case are 1 00+0.50 mm and 2200+0.10 mm respectively.NOTE 2This particu
33、lar test is allowed because a substantial amount of data exists for this specimen and test geometry. This MCVN specimen is notproportional to the CVN specimen, so scaling is not appropriate.5.6 The testing machine shall be a pendulum type of rigid construction. All general requirements for apparatus
34、 and calibrationspecified in Test Methods E23 shall be satisfied.5.7 For instrumented force measurements using optional force measuring instrumentation, the requirements given in TestMethod E2298 regarding striker instrumentation, data acquisition, and data analysis shall be satisfied.E2248 1326. Ha
35、zards6.1 Safety precautions should be taken to protect personnel from electric shock, the swinging pendulum, flying brokenspecimens, and hazards associated with specimen warming and cooling media. See also 1.6.FIG. 1 Scaled 8 mm and 2 mm Strikers for Use in Miniaturized Charpy Impact TestingNOTE 1Pe
36、rmissible variations shall be as follows:Angle of striker 1Radius of curvature of striking edge Nominal 1 mm Striker: +0.25, 0Nominal 4 mm Striker: 0.025 mmRadius of curvature of striking edgeNominal 1 mm Striker: +0.25, 0mmNominal 4 mm Striker: 0.025 mmRadius of shoulder of nominal 4 mm striker0.02
37、5 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 90 10 minLigament length 0.025 mmCross section dimensions 0.025 mmFinish requirements 2m notched surface/opposite surface4m other surfacesF
38、inish requirements 2m notched surface/opposite surface4m other surfacesLength of specimen +0. -12mmLength of specimen +0, -0.12mmCentering of notch 0.12 mmAngle of notch 1FIG. 2 Nominal 12-Scale Miniaturized Charpy Impact SpecimenE2248 1337. Test Specimens7.1 The recommended proportional specimen co
39、nfiguration is the square cross section notched bar shown in Fig. 2. The crosssectional dimension is slightly under 5 mm to enable machining from a previously tested CVN. Information on additional specimengeometries that have been successfully used is provided in Appendix X1.NOTE 3In case MCVN speci
40、mens are extracted from broken CVN specimens of highly ductile materials, the user should ensure that the severe plasticdeformation occurred during fracture of the CVN specimens does not affect the impact behavior of the miniaturized samples.7.2 Microstructural considerations dictate that only V-not
41、ch specimens with cross sectional dimensions sufficient to ensure arepresentative volume of material is tested may be used. In order to satisfy this requirement, the size scale and mean separationdistance of inhomogeneities that exist in the material must be known. The cross sectional dimension must
42、 be at least five timesgreater than the largest inhomogeneity. Post-test metallography may be performed in order to confirm that the requirement has beenmet.7.3 Stress field similitude dictates that if the miniaturized specimens (such as the one shown in Fig. 2) do not satisfy themicrostructural con
43、siderations, specimens with a larger cross section may be used. For the square cross section specimen in Fig.2, all the remaining specimen dimensions (length, notch depth, etc.) shall be scaled by appropriate ratio with the conventional CVNdimensions. This has the advantage of standardization of app
44、roach and scalability of previously calculated finite element solutions.7.4 Machining the outside surfaces of the MCVN specimens using continuous wire electric discharge machining (EDM) or anyother machining method which produces less than 0.005 mm of disturbed material on the surface is acceptable.
45、acceptable (1). Thecrack starter notch shall be EDM machined or precision ground.7.5 Side grooving of the MCVN specimens (see also Appendix X2) is optional. Investigations (1)(see Appendix X2) haveshown that the use of side grooves on MCVN specimens provides a larger volume of material which is samp
46、led at plane strainconditions. This results in less downward shift in temperature due to loss of constraint caused by miniaturization, and therebyreduces the need for correction factors to simulate CVN transitional fracture temperature dependence.7.6 The choice of specimen depends on the application
47、.NOTE 4Although this test method specifically addresses impact tests performed on notched specimens, the use of unnotched samples may beadvantageous when testing refractory metals or materials produced by powder metallurgy methods. For such materials, machining an accurate notchwithout producing sig
48、nificant damage is extremely difficult. The use of unnotched specimens, however, is outside the scope of this test method.7.6.1 For some materials, the use of different methods for machining specimens may increase results variability and data scatter.For this reason, the machining method used shall
49、be reported (see 11.1.2). Performing microstructural investigations in order todetermine the depth of the recast layer might be helpful.8. Test Procedure8.1 The test procedure may be summarized as follows: the test specimen is heated/cooled in situ (that is, at the impact location)or it is removed from its cooling (or heating) medium, and positioned on the specimen supports; the pendulum is released withminimum vibration; and the absorbed energy is recorded from the machine dial or, preferably, from the optical encoder. Forinstrumented te
