1、Designation: E2298 15Standard Test Method forInstrumented Impact Testing of Metallic Materials1This standard is issued under the fixed designation E2298; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、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 establishes the requirements for per-forming instrumented Charpy V-Notch (CVN) and instru-mented Miniaturized Charpy
3、V-Notch (MCVN) impact tests onmetallic materials. This method, which is based on experiencedeveloped testing steels, provides further information (inaddition to the total absorbed energy) on the fracture behaviorof the tested materials. Minimum requirements are given formeasurement and recording equ
4、ipment such that similar sen-sitivity and comparable total absorbed energy measurements tothose obtained in Test Methods E23 and E2248 are achieved.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not p
5、urport 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 applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2
6、A370 Test Methods and Definitions for Mechanical Testingof Steel ProductsE4 Practices for Force Verification of Testing MachinesE23 Test Methods for Notched Bar Impact Testing of Me-tallic MaterialsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting
7、an Interlaboratory Study toDetermine the Precision of a Test MethodE2248 Test Method for Impact Testing of MiniaturizedCharpy V-Notch Specimens2.2 ISO Standard:ISO 14556 SteelCharpy V-notch Pendulum ImpactTestsInstrumented Test Method33. Terminology3.1 DefinitionsThe symbols and definitions applicab
8、le toinstrumented impact testing are indicated in Table 1.4. Summary of Test Method4.1 This test method prescribes the requirements for instru-mented CVN and MCVN impact tests in accordance with TestMethods E23 and E2248. The E23 and E2248 tests consist ofbreaking by one blow from a swinging pendulu
9、m, underconditions defined hereafter, a specimen notched in the middleand supported at each end. In order to establish the impactforce-displacement diagram, it is necessary to instrument thestriker with strain gages4and measure the voltage as a functionof time during the impact event. The voltage-ti
10、me curve isconverted to the force-time curve through a suitable staticcalibration. The force-displacement relationship is then ob-tained by double integration of the force-time curve. The areaunder the force-displacement curve corresponds to the energyabsorbed by the specimen during the test.4.2 For
11、ce-displacement curves for different steels and dif-ferent temperatures can vary even though the areas under thecurves and the absorbed energies are identical. If the force-displacement curves are divided into a number of characteristicparts, various phases of the test with characteristic forces,dis
12、placements, and energies can be deduced. These character-istic values provide additional information about the fracturebehavior of the specimen.4.3 Application of instrumented test data to the evaluationof material behavior is the responsibility of the user of this testmethod.5. Significance and Use
13、5.1 Instrumented impact testing provides an independentmeasurement of the total absorbed energy associated with1This test method is under the jurisdiction of ASTM Committee E28 onMechanical Testing and is the direct responsibility of Subcommittee E28.07 onImpact Testing.Current edition approved Oct.
14、 1, 2015. Published December 2015. Originallyapproved in 2009. Last previous edition approved in 2013 as E229813a. DOI:10.1520/E2298-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume in
15、formation, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4This test method refers to strikers instrumented with strain gages. However, theuse of piezoelect
16、ric load cells or accelerometers is not excluded, provided theirtemperature sensitivity is properly accounted for.*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 States1fractur
17、ing CVN or MCVN specimens for test machinesequipped with a dial and/or optical encoder.5.2 Instrumented impact testing is particularly effective inMCVN testing since the resolution of a calibrated strain-gagedstriker does not necessarily decrease with the magnitude of themeasured energy.5.3 In addit
18、ion to providing an measure of total absorbedenergy (Wt), instrumented testing enables the determination ofcharacteristic force, energy, and displacement parameters.Depending on the material and test temperature, these param-eters can provide very useful information (in addition to totalabsorbed ene
19、rgy) on the fracture behavior of materials such as:the temperature which corresponds to the onset of the lowershelf; the temperature which corresponds to the onset of theupper shelf; the pre-maximum force energy (Wm); the post-maximum force energy; the energy associated with shear liptearing after b
20、rittle fracture; the general yield force (Fgy); theforce at brittle fracture initiation (Fbf); the arrest force (Fa).Theinstrumented data may also be used to highlight test resultswhich should be discarded on the basis of misalignment orother critical test factors.6. Precautions in Operation of the
21、Machine6.1 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 1.3.7. Apparatus7.1 The test shall be carried out in accordance with TestMethods E23 or E2248
22、using a pendulum impact testingmachine which is instrumented to determine force-time orforce-displacement curves.7.1.1 For instrumented CVN testing, the use of an instru-mented striker conforming to the specifications of ISO 14556(i.e., 2 mm radius of striking edge) is allowed. Available data(1, 2)5
23、indicate that the influence of striker geometry oninstrumented CVN forces is not very significant.7.2 Force Measurement:7.2.1 Force measurement is achieved by using an electronicsensor (piezoelectric load cell, strain gage load cell or a forcemeasurement derived from an accelerometer).7.2.2 The forc
24、e measuring system (including strain gages,wiring, and amplifier) shall have an upper frequency bound ofat least 100 kHz for CVN tests and 250 kHz for MCVN tests.For MCVN tests, if only absorbed energy has to be measuredfrom the curve, an upper frequency limit of 100 kHz issufficient. The upper freq
25、uency bound for the system shall beverified by measurement or analysis. Measurements can bemade using a function generator which is wired directly to thestrain gage bridge.7.2.3 The signal shall be recorded without filtering. Post-testfiltering, however, is allowed.7.2.4 Calibration of the recorder
26、and measurement systemmay be performed statically in accordance with the accuracyrequirements given below. It is recommended that the forcecalibration be performed with the striker attached to thependulum assembly. The strain gage signal conditioningequipment, cables, and recording device shall be u
27、sed in thecalibration. In most cases, a computer is used for dataacquisition and the calibration shall be performed with thevoltage read from the computer. The intent is to calibratethrough the electronics and cables which are used during actualtesting. Force is applied to the striker by using a sui
28、table loadframe with a load cell verified in accordance with Practices E4.7.2.4.1 The static linearity and hysteresis error of thebuilt-in, instrumented striker, including all parts of the mea-surement system up to the recording apparatus (printer, plotter,etc.), shall be within 62 % of the recorded
29、 force, between 50and 100 % of the nominal force range, and within 61 % of thefull scale force value between 10 and 50 % of the nominalforce range (see Fig. 1).7.2.4.2 The instrumented striker system shall be calibratedto ensure accurate force readings are obtained over the nominalforce range which
30、will be encountered in testing. The straingaged system shall be designed to minimize its sensitivity tonon-symmetric loading.7.2.5 Calibration shall be performed if the instrumentedstriker has undergone dismantling or repair, unless it can beshown that removal of the striker from the test machine, a
31、ndsubsequent reattachment to the machine, does not affect thecalibration. Calibration shall also be performed under thecircumstances described below.7.2.6 Requirements on Absorbed EnergyFor each test inwhich the entire force signal has been recorded (i.e., until theforce returns to the baseline), th
32、e difference between absorbedenergy given by the dial and/or optical encoder KV and thetotal impact energy Wtshall be within 15 % or 1 J, whicheveris larger. If this requirement is not met but the difference doesnot exceed 25 % or 2 J, whichever is larger, force values shall5The boldface numbers in
33、parentheses refer to the list of references at the end ofthis standard.TABLE 1 Symbols and Designations Related to InstrumentedImpact TestingSymbol Definition UnitFaForce at end of unstable crack propagation (arrestforce)NFgyGeneral yield force NFmMaximum force NFbfForce at initiation of brittle fra
34、cture (unstable crackpropagation)Ng Local acceleration due to gravity m/s2h0Initial falling height of the striker mKV Absorbed energy measured from the machine dial orencoderJm Total effective mass of moving striker kgsaDisplacement at end of unstable crack propagation(arrest force)msgyDisplacement
35、at general yield msmDisplacement at maximum force msbfDisplacement at initiation of brittle fracture mstDisplacement at end of force-displacement curve mt0Time at the beginning of deformation of the specimen sv0Initial striker impact velocity ms-1WaPartial impact energy from F =0toF = FaJWbfPartial
36、impact energy from F =0toF = FbfJWmPartial impact energy from F =0toF = FmJWtTotal impact energy JE2298 152be adjusted until KV = Wtwithin 0.01 J (3). If the differenceexceeds 25 % or 2 J, whichever is larger, the test shall bediscarded and the user shall check and if necessary repeat thecalibration
37、 of the instrumented striker. If recording of the entireforce signal is not possible (for example due to the specimenbeing ejected from the machine without being fully broken),the user shall demonstrate conformance to the requirementsabove by testing at least five Charpy specimens of anyequivalent m
38、aterial.NOTE 1Specimens with certified values of maximum force (Fm) canbe tested to verify the accuracy of the force values measured by theinstrumented striker. Dynamic impact force verification specimens areavailable6with certified Fmvalues of 24.06 kN and 33.00 kN. Thesevalues have been establishe
39、d at room temperature through an interlabo-ratory study (4) involving six international laboratories, see also 13.1.3.The same verification specimens can also be used to verify the absorbedenergy scale of the impact machine in accordance with Test Methods E23at either -40 C 6 1 C or room temperature
40、 (21 C 6 1 C).7.3 Displacement Determination:7.3.1 Displacement is normally determined by converting astrain gage voltage-time measurement to a force-time measure-ment. The force-time relationship is proportional to the accel-eration as a function of time. Given an assumed rigid striker ofmass m, th
41、e initial impact velocity v0, the time t following thebeginning of the deformation at t0, and expressing the velocityas a function of time by v(t), the specimen bending displace-ment s(t) is calculated by double numerical integration asfollows:vt! 5 v021mt*t0Ft!dt (1)st! 5t*t0vt!dt (2)7.3.2 The init
42、ial impact velocity needed to perform theabove integrations may be calculated from:v05 =2gh0(3)where:g = the local acceleration due to gravity, andh0= the falling height of the striker.7.3.2.1 Alternatively, the velocity signal registered when thependulum passes through its lowest position and strik
43、es thespecimen can be optically measured directly to determine v0.7.3.3 Displacement can also be determined by non-contacting measurement of the displacement of the strikerrelative to the anvil using optical, inductive, or capacitivemethods. The signal transfer characteristics of the displace-ment m
44、easurement system must correspond to that of the forcemeasuring system in order to make the two recordings syn-chronous. The displacement measuring system shall be de-signed for nominal values of up to 30 mm. Linearity errors inthe measuring system shall yield measured values to within+2 % in the ra
45、nge 130 mm. Measurements between zero and1 mm may not be sufficiently accurate to determine thedisplacement. In such cases, it is recommended that thedisplacement of the specimen be determined from time mea-surement and the striker impact velocity as indicated in Eq 1and 2.7.4 Recording Apparatus:7.
46、4.1 The minimum data acquisition requirement is a 10-bitanalog-digital converter with a minimum sampling rate of 1000data points per millisecond. However, 12-bit or more isrecommended. A minimum storage capacity of 8000 datapoints is required.6The sole source of supply of the specimens known to the
47、committee at this timeis NIST. If interested, email charpyboulder.nist.gov. If you are aware ofalternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may
48、attend.FIG. 1 Allowable Errors in Force MeasurementsE2298 1537.4.2 The total absorbed energy measured using instrumen-tation shall be compared with that shown by the machine dial(only for CVN testing), or preferably, by comparison with anoptical encoder (for both CVN and MCVN testing). If totalabsor
49、bed energy is measured using a machine dial or opticalencoder, then this data shall be reported along with theinstrumented striker energy. For requirements on absorbedenergy based on the comparison between KV and Wt, refer to7.2.6.8. Test Specimens8.1 The CVN specimens shall be in accordance with TestMethod E23. The MCVN specimens shall be in accordancewith Test Method E2248.9. Procedure9.1 Specimen TestingThe test is performed in the sameway as the CVN or MCVN impact test according to TestMethods E23 or E2248, respectively. In addition, the voltage-time curve is m
