1、Designation: E2298 09E2298 13Standard 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 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 standard test method establishes the requirements for performing instrumented Charpy V-Notch (CVN) andinstrumented Miniatu
3、rized Charpy V-Notch (MCVN) impact tests on metallic materials. This method, which is based onexperience developed testing steels, provides further information (in addition to the total absorbed energy) on the fracture behaviorof the tested materials. Minimum requirements are given for measurement a
4、nd recording equipment such that similar sensitivityand comparable total absorbed energy measurements to those obtained in Test Methods E23 and E2248 are achieved.1.2 The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.1.3 Thi
5、s standard does not purport to address all of the safety concerns, if any, associated with 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
6、.1 ASTM Standards:2A370 Test Methods and Definitions for Mechanical Testing of Steel ProductsE4 Practices for Force Verification of Testing MachinesE23 Test Methods for Notched Bar Impact Testing of Metallic MaterialsE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE691 Prac
7、tice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodE2248 Test Method for Impact Testing of Miniaturized Charpy V-Notch Specimens2.2 ISO Standard:ISO 14556 SteelCharpy V-notch Pendulum Impact TestsInstrumented Test Method33. Terminology3.1 DefinitionsThe symbols a
8、nd definitions applicable to instrumented impact testing are indicated in Table 1.4. Summary of Test Method4.1 This test method prescribes the requirements for instrumented CVN and MCVN impact tests in accordance with TestMethods E23 and E2248. The E23 and E2248 tests consist of breaking by one blow
9、 from a swinging pendulum, under conditionsdefined hereafter, a specimen notched in the middle and supported at each end. In order to establish the impact force-displacementdiagram, it is necessary to instrument the striker with strain gages4 and measure the voltage as a function of time during the
10、impactevent. The voltage-time curve is converted to the force-time curve through a suitable static calibration. The force-displacementrelationship is then obtained by double integration of the force-time curve. The area under the force-displacement curvecorresponds to the energy absorbed by the spec
11、imen during the test.4.2 Force-displacement curves for different steels and different temperatures can vary even though the areas under the curvesand the absorbed energies are identical. If the force-displacement curves are divided into a number of characteristic parts, various1 This test method is
12、under the jurisdiction of ASTM Committee E28 on Mechanical Testing and is the direct responsibility of Subcommittee E28.07 on Impact Testing.Current edition approved April 1, 2009April 1, 2013. Published April 2009April 2013. Originally approved in 2009. Last previous edition approved in 2009 as E22
13、9809.DOI: 10.1520/E2298-09.10.1520/E2298-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, 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
14、American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.4 This test method refers to strikers instrumented with strain gages. However, the use of piezoelectric load cells or accelerometers is not excluded, provided theirtemperature sensitivity
15、is properly accounted for.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 recommends th
16、at 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 States1phases of the test wit
17、h characteristic forces, displacements, and energies can be deduced. These characteristic values provideadditional information about the fracture behavior of the specimen.4.3 Application of instrumented test data to the evaluation of material behavior is the responsibility of the user of this testme
18、thod.5. Significance and Use5.1 Instrumented impact testing provides an independent measurement of the total absorbed energy associated with fracturingCVN or MCVN specimens for test machines equipped with a dial and/or optical encoder.TABLE 1 Symbols and Designations Related to InstrumentedImpact Te
19、stingCOLSPEC/colname=“col3“ align=“center“Symbol Definition UnitFa Force at end of unstable crackpropagation (arrest force)NFa Force at end of unstable crackpropagation (arrest force)NFgy General yield force NFgy General yield force NFm Maximum force NFm Maximum force NFbf Force at initiation of bri
20、ttle fracture(unstable crack propagation)NFbf Force at initiation of brittle fracture(unstable crack propagation)Ng Local acceleration due to gravity m/s2g Local acceleration due to gravity m/s2h0 Initial falling height of the striker mh0 Initial falling height of the striker mKV Absorbed energy mea
21、sured fromthe machine dial or encoderJm Total effective mass of movingstrikerkgm Total effective mass of movingstrikerkgsa Displacement at end of unstablecrack propagation (arrest force)msa Displacement at end of unstablecrack propagation (arrest force)msgy Displacement at general yield msgy Displac
22、ement at general yield msm Displacement at maximum force msm Displacement at maximum force msbf Displacement at initiation of brittlefracturemsbf Displacement at initiation of brittlefracturemst Displacement at end of force-displacement curvemst Displacement at end of force-displacement curvemt0 Tim
23、e at the beginning ofdeformation of the specimenst0 Time at the beginning ofdeformation of the specimensv0 Initial striker impact velocity ms-1v0 Initial striker impact velocity ms-1Wa Partial impact energy from F = 0 toF = FaJWa Partial impact energy from F = 0 toF = FaJWbf Partial impact energy fr
24、om F = 0 toF = FbfJWbf Partial impact energy from F = 0 toF = FbfJWm Partial impact energy from F = 0 toF = FmJWm Partial impact energy from F = 0 toF = FmJWt Total impact energy JWt Total impact energy JE2298 1325.2 Instrumented impact testing is particularly effective in MCVN testing since the res
25、olution of a calibrated strain-gaged strikerdoes not necessarily decrease with the magnitude of the measured energy.5.3 In addition to providing an measure of total absorbed energy (Wt), instrumented testing enables the determination ofcharacteristic force, energy, and displacement parameters. Depen
26、ding on the material and test temperature, these parameters canprovide very useful information (in addition to total absorbed energy) on the fracture behavior of materials such as: the temperaturewhich corresponds to the onset of the lower shelf; the temperature which corresponds to the onset of the
27、 upper shelf; thepre-maximum force energy (Wm); the post-maximum force energy; the energy associated with shear lip tearing after brittle fracture;the general yield force (Fgy); the force at brittle fracture initiation (Fbf); the arrest force (Fa). The instrumented data may also beused to highlight
28、test results which should be discarded on the basis of misalignment or other critical test factors.6. Precautions in Operation of the Machine6.1 Safety precautions should be taken to protect personnel from electric shock, the swinging pendulum, flying brokenspecimens, and hazards associated with spe
29、cimen warming and cooling media. See also 1.3.7. Apparatus7.1 The test shall be carried out according to in accordance with Test Methods E23 or E2248 using a pendulum impact testingmachine which is instrumented to determine force-time or force-displacement curves.7.1.1 For instrumented CVN testing,
30、the use of an instrumented striker conforming to the specifications of ISO 14556 (i.e., 2mm radius of striking edge) is allowed.Available data (1, 2)5 indicate that the influence of striker geometry on instrumented CVNforces is not very significant.7.2 Force Measurement:7.2.1 Force measurement is ac
31、hieved by using an electronic sensor (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 of at least100 kHz for CVN tests and 250 kHz
32、for MCVN tests. For MCVN tests, if only absorbed energy has to be measured from the curve,an upper frequency limit of 100 kHz is sufficient. The upper frequency bound for the system shall be verified by measurement oranalysis. Measurements can be made using a function generator which is wired direct
33、ly to the strain gage bridge.7.2.3 The signal shall be recorded without filtering. Post-test filtering, however, is allowed.7.2.4 Calibration of the recorder and measurement system may be performed statically in accordance with the accuracyrequirements given below. It is recommended that the force c
34、alibration be performed with the striker attached to the pendulumassembly. The strain gage signal conditioning equipment, cables, and recording device shall be used in the calibration. In mostcases, a computer is used for data acquisition and the calibration shall be performed with the voltage read
35、from the computer. Theintent is to calibrate through the electronics and cables which are used during actual testing. Force is applied to the striker by usinga suitable load frame with a load cell verified in accordance with Practices E4.7.2.4.1 The static linearity and hysteresis error of the built
36、-in, instrumented striker, including all parts of the measurementsystem up to the recording apparatus (printer, plotter, etc.), shall be within 62 % of the recorded force, between 50 and 100 % ofthe nominal force range, and within 61 % of the full scale force value between 10 and 50 % of the nominal
37、 force range (see Fig.1).7.2.4.2 The instrumented striker system shall be calibrated to ensure accurate force readings are obtained over the nominal forcerange which will be encountered in testing. The strain gaged system shall be designed to minimize its sensitivity to non-symmetricloading.7.2.5 Ca
38、libration shall be performed if the instrumented striker has undergone dismantling or repair, unless it can be shown thatremoval of the striker from the test machine, and subsequent reattachment to the machine, does not affect the calibration.Calibration shall also be performed under the circumstanc
39、es described below.7.2.6 Requirements on Absorbed EnergyFor each test in which the entire force signal has been recorded (i.e., until the forcereturns to the baseline), the difference between absorbed energy given by the dial and/or optical encoder KV and the total impactenergy Wt shall be within 15
40、 % or 1 J, whichever is larger. If this requirement is not met but the difference does not exceed 25 %or 2 J, whichever is larger, force values shall be adjusted until KV = Wt within 0.01 J (3). If the difference exceeds 25 % or 2 J,whichever is larger, the test shall be discarded and the user shall
41、 check and if necessary repeat the calibration of the instrumentedstriker. If recording of the entire force signal is not possible (for example due to the specimen being ejected from the machinewithout being fully broken), the user shall demonstrate conformance to the requirements above by testing a
42、t least five Charpyspecimens of any equivalent material.7.2.7 In order to verify the accuracy of the force values measured by the instrumented striker, dynamic impact force verificationspecimens are available, corresponding to maximum force (Fm) levels of 24 kN and 33 kN. These specimens are supplie
43、d by NISTin Boulder, CO as SRM 2112 (24 kN) and SRM 2113 (33 kN), and can also be used to verify the absorbed energy scale of the5 The boldface numbers in parentheses refer to the list of references at the end of this standard.E2298 133impact machine in accordance with Test Methods E23 at -40 C 6 1
44、C (low and high energy specimens) and room temperature(21 C 6 1 C, super-high energy specimens). The certified Fm values have been established at room temperature through aninterlaboratory study (4) involving six international laboratories, see also 13.1.3.7.3 Displacement Determination:7.3.1 Displa
45、cement is normally determined by converting a strain gage voltage-time measurement to a force-time measurement.The force-time relationship is proportional to the acceleration as a function of time. Given an assumed rigid striker of mass m, theinitial impact velocity v0, the time t following the begi
46、nning of the deformation at t0, and expressing the velocity as a function oftime by v(t), the specimen bending displacement s(t) is calculated by double numerical integration as follows:vt!5v02 1mt*t0Ft!dt (1)st!5t*t0vt!dt (2)7.3.2 The initial impact velocity needed to perform the above integrations
47、 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 the pendulum passes through its lowest position and strikes thespecimen can be optically measured directly to dete
48、rmine v0.7.3.3 Displacement can also be determined by non-contacting measurement of the displacement of the striker relative to theanvil using optical, inductive, or capacitive methods. The signal transfer characteristics of the displacement measurement systemmust correspond to that of the force mea
49、suring system in order to make the two recordings synchronous. The displacementmeasuring system shall be designed for nominal values of up to 30 mm. Linearity errors in the measuring system shall yieldmeasured values to within +2 % in the range 130 mm. Measurements between zero and 1 mm may not be sufficiently accurateto determine the displacement. In such cases, it is recommended that the displacement of the specimen be determined from timemeasurement and the striker impact velocity as indicated in Eq 1 and 2.7.4 Recording Apparatus:7.4.1 The minimum data acquisiti
