ASTM E2298-2018 Standard Test Method for Instrumented Impact Testing of Metallic Materials.pdf

1、Designation: E2298 18Standard 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 absorbed energy) on the fracture behavior of thetested materials. Minimum requirements are given for mea-surement and recording equipme

4、nt such that similar sensitivityand comparable absorbed energy measurements to those ob-tained 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 purport to

5、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, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was d

6、eveloped in accor-dance with internationally recognized principles on standard-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

7、Documents2.1 ASTM Standards:2E4 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 an Interlaboratory Study toDetermine the Pre

8、cision 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 applicable toinstrumented impact testing are indicat

9、ed 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 pendulum, underconditions defined hereafter, a spec

10、imen 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-time curve isconverted to the force-time curve

11、 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 instru-mented absorbed energy of the broken specimen.4.2 Force-displacement curves for different s

12、teels 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,displacements, and partial instrumented a

13、bsorbed energies canbe deduced. These characteristic values provide additionalinformation about the fracture behavior of the specimen.4.3 Application of instrumented test data to the evaluationof material behavior is the responsibility of the user of this testmethod.1This test method is under the ju

14、risdiction of ASTM 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 E229815. DOI:10.1520/E2298-18.2For ref

15、erenced 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.3Available from American National Standards Institute (ANSI), 25 W. 4

16、3rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4This test method refers to strikers instrumented with strain gages. However, theuse of piezoelectric load cells or accelerometers is not excluded, provided theirtemperature sensitivity is properly accounted for.*A Summary of Changes section

17、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 in accordance with internationally recognized principles on standardization established in the Decision on Pri

18、nciples for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15. Significance and Use5.1 Instrumented impact testing provides an independentmeasurement of the absorbed energy associated with fract

19、uringCVN or MCVN specimens for test machines equipped with adial or optical encoder, or both.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 force.5.3 In

20、addition to providing a measure of instrumentedabsorbed energy (Wt), instrumented testing enables the deter-mination of characteristic force, partial instrumented absorbedenergy, and displacement parameters. Depending on the mate-rial and test temperature, these parameters can provide veryuseful inf

21、ormation (in addition to instrumented absorbed en-ergy) on the fracture behavior of materials such as: thetemperature which corresponds to the onset of the lower shelf;the temperature which corresponds to the onset of the uppershelf; partial instrumented absorbed energy up to the maximumforce (Wm);

22、partial instrumented absorbed energy up to theforce at brittle fracture initiation (Wbf); the partial instrumentedabsorbed energy after the maximun force (WtWm); the generalyield force (Fgy); the force at brittle fracture initiation (Fbf); thearrest force (Fa). The instrumented data may also be used

23、 tohighlight test results which should be discarded on the basis ofmisalignment or other critical test factors.6. Precautions in Operation of the Machine6.1 Safety precautions should be taken to protect personnelfrom electric shock, the swinging pendulum, flying brokenspecimens, and hazards associat

24、ed 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 using a pendulum impact testingmachine which is instrumented to determine force-time orforce-displacement curves.7.1.1 For instrumented CVN testing, the u

25、se 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)5indicate that the influence of striker geometry oninstrumented CVN forces is not very significant.7.2 Force Measurement:7.2.1 Force measurement is achieve

26、d by using an electronicsensor (piezoelectric load cell, strain gage load cell or a forcemeasurement derived from an accelerometer).7.2.2 The force 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 MCV

27、N tests.For MCVN tests, if only instrumented absorbed energy has tobe measured from the curve, an upper frequency limit of 100kHz is sufficient. The upper frequency bound for the systemshall be verified by measurement or analysis. Measurementscan be made using a function generator which is wired dir

28、ectlyto the strain gage bridge.7.2.3 The signal shall be recorded without filtering. Post-testfiltering, however, is allowed.7.2.4 Calibration of the recorder and measurement systemmay be performed statically in accordance with the accuracyrequirements given below. It is recommended that the forceca

29、libration be performed with the striker attached to thependulum assembly. The strain gage signal conditioningequipment, cables, and recording device shall be used in thecalibration. In most cases, a computer is used for dataacquisition and the calibration shall be performed with thevoltage read from

30、 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 suitable loadframe with a load cell verified in accordance with Practices E4.7.2.4.1 The static linearity and hysteresis error of thebuilt-in, i

31、nstrumented striker, including all parts of the mea-surement system up to the recording apparatus (printer, plotter,etc.), shall be within 62 % of the recorded force, between 50and 100 % of the nominal force range, and within 61 % of thefull scale force value between 10 and 50 % of the nominalforce

32、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 will be encountered in testing. The straingaged system shall be designed to minimize its sensitivity tonon-symmetric loading.5The boldface nu

33、mbers in 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 br

34、ittle fracture (unstable crackpropagation)Ng Local acceleration due to gravity m/s2h0Initial falling height of the striker mKV Absorbed energyWork spent to fracture a specimenin a single pendulum swing, as measured by acompensated indicating deviceJm Total effective mass of moving striker kgsaDispla

35、cement at end of unstable crack propagation(arrest force)msgyDisplacement 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

36、 impact velocity ms-1WaPartial instrumented absorbed energy from F =0toF = FaJWbfPartial instrumented absorbed energy from F =0toF = FbfJWmPartial instrumented absorbed energy from F =0toF = FmJWtInstrumented absorbed energy work spent tofracture a specimen in a single pendulum swing, ascalculated b

37、y integrating the force-displacementcurveJSFA Shear fracture appearance the amount of fracturesurface in the specimen that failed in a shear (stable)mode%E2298 1827.2.5 Calibration shall be performed if the instrumentedstriker has undergone dismantling or repair, unless it can beshown that removal o

38、f the striker from the test machine, andsubsequent reattachment to the machine, does not affect thecalibration. Calibration shall also be performed under thecircumstances described below.7.2.6 Requirements on Instrumented Absorbed EnergyForeach test in which the entire force signal has been recorded

39、(that is, until the force returns to the baseline), the differencebetween absorbed energy given by the dial or optical encoder,or both, KV and the instrumented absorbed energy Wtshall bewithin 15 % or 1 J, whichever is larger. If this requirement isnot met but the difference does not exceed 25 % or

40、2 J,whichever is larger, force values shall be adjusted until KV =Wtwithin 0.01 J (3). If the difference exceeds 25 % or 2 J,whichever is larger, the test shall be discarded and the usershall check and if necessary repeat the calibration of theinstrumented striker. If recording of the entire force s

41、ignal isnot possible (for example due to the specimen being ejectedfrom the machine without being fully broken), the user shalldemonstrate conformance to the requirements above by testingat least five Charpy specimens of any equivalent material.NOTE 1Specimens with certified values of maximum force

42、(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 established at room temperature through an interlabo-ratory study (4) inv

43、olving six international laboratories, see also 13.1.3.The same verification specimens can also be used for indirect verificationof the impact machine in accordance with Test Methods E23.7.3 Displacement Determination:7.3.1 Displacement is normally determined by converting astrain gage voltage-time

44、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, the initial impact velocity v0, the time t following thebeginning of the deformation at t0, and expressing the velocityas a funct

45、ion 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 initial impact velocity needed to perform theabove integrations may be calculated from:v05 =2gh0(3)where:g = the local acceleration

46、 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 strikes thespecimen can be optically measured directly to determine v0.7.3.3 Displacement can also be determined by non-contacting m

47、easurement of the displacement of the strikerrelative to the anvil using optical, inductive, or capacitivemethods. The signal transfer characteristics of the displace-ment measurement system must correspond to that of the forcemeasuring system in order to make the two recordings syn-chronous. The di

48、splacement measuring system shall be de-signed for nominal values of up to 30 mm. Linearity errors inthe measuring system shall yield measured values to within6The sole source of supply of the specimens known to the committee at this timeis NIST. If interested, email charpyboulder.nist.gov. If you a

49、re 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 attend.FIG. 1 Allowable Errors in Force MeasurementsE2298 183+2 % in the range 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 R