1、Designation: E2298 13E2298 13aStandard 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 rev
2、ision. 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 establishes the requirements for performing instrumented Charpy V-Notch (CVN) and instrumentedMiniaturized Ch
3、arpy V-Notch (MCVN) impact tests on metallic materials. This method, which is based on experience developedtesting steels, provides further information (in addition to the total absorbed energy) on the fracture behavior of the tested materials.Minimum requirements are given for measurement and recor
4、ding equipment such that similar sensitivity and comparable totalabsorbed 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 standard. No other units of measurement are included in this standard.1.3 This standard d
5、oes 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 Documents2.1 ASTM Stan
6、dards: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 Practice for Con
7、ducting 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 and definitio
8、ns 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 from a swin
9、ging 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 impactevent.
10、 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 specimen during
11、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 under the ju
12、risdiction of ASTM Committee E28 on Mechanical Testing and is the direct responsibility of Subcommittee E28.07 on Impact Testing.Current edition approved April 1, 2013Nov. 1, 2013. Published April 2013November 2013. Originally approved in 2009. Last previous edition approved in 20092013 asE229809.13
13、. DOI: 10.1520/E2298-13.10.1520/E2298-13A.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 Am
14、erican 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 is
15、 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 that
16、 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 with
17、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 testmeth
18、od.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.5.2 Instrumented impact testing is particularly effective in MCVN t
19、esting since the resolution 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 displaceme
20、nt parameters. Depending 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
21、 to the onset of the 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
22、beused to highlight 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
23、 associated with specimen warming and cooling media. See also 1.3.7. Apparatus7.1 The test shall be carried out in accordance with Test Methods E23 or E2248 using a pendulum impact testing machine whichis instrumented to determine force-time or force-displacement curves.7.1.1 For instrumented CVN te
24、sting, 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 measuremen
25、t is achieved by using an electronic sensor (piezoelectric load cell, strain gage load cell or a forcemeasurement derived from an accelerometer).5 The boldface numbers in parentheses refer to the list of references at the end of this standard.TABLE 1 Symbols and Designations Related to InstrumentedI
26、mpact TestingSymbol Definition UnitFa Force at end of unstable crack propagation (arrestforce)NFgy General yield force NFm Maximum force NFbf Force at initiation of brittle fracture (unstable crackpropagation)Ng Local acceleration due to gravity m/s2h0 Initial falling height of the striker mKV Absor
27、bed energy measured from the machine dial orencoderJm Total effective mass of moving striker kgsa Displacement at end of unstable crack propagation(arrest force)msgy Displacement at general yield msm Displacement at maximum force msbf Displacement at initiation of brittle fracture mst Displacement a
28、t end of force-displacement curve mt0 Time at the beginning of deformation of the specimen sv0 Initial striker impact velocity ms-1Wa Partial impact energy from F = 0 to F = Fa JWbf Partial impact energy from F = 0 to F = Fbf JWm Partial impact energy from F = 0 to F = Fm JWt Total impact energy JE2
29、298 13a27.2.2 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 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 s
30、ufficient. The upper frequency bound for the system shall be verified by measurement oranalysis. Measurements can be made using a function generator which is wired directly to the strain gage bridge.7.2.3 The signal shall be recorded without filtering. Post-test filtering, however, is allowed.7.2.4
31、Calibration of the recorder and measurement system may be performed statically in accordance with the accuracyrequirements given below. It is recommended that the force calibration be performed with the striker attached to the pendulumassembly. The strain gage signal conditioning equipment, cables,
32、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 from the computer. Theintent is to calibrate through the electronics and cables which are used during actual testing. Force is app
33、lied 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-in, instrumented striker, including all parts of the measurementsystem up to the recording apparatus (printer, plotter, etc.), sh
34、all 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 force range (see Fig.1).7.2.4.2 The instrumented striker system shall be calibrated to ensure accurate force readings are obtaine
35、d 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 Calibration shall be performed if the instrumented striker has undergone dismantling or repair, unless it can be shown thatremoval o
36、f the striker from the test machine, and subsequent reattachment to the machine, does not affect the calibration.Calibration shall also be performed under the circumstances described below.7.2.6 Requirements on Absorbed EnergyFor each test in which the entire force signal has been recorded (i.e., un
37、til 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 % 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,
38、 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 check and if necessary repeat the calibration of the instrumentedstriker. If recording of the entire force signal is not possible
39、 (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 at least five Charpyspecimens of any equivalent material.NOTE 1Specimens with certified values of maximum force (Fm) can be tested
40、to verify the accuracy of the force values measured by the instrumentedstriker. Dynamic impact force verification specimens are available6 with certified Fm values of 24.06 kN and 33.00 kN.These values have been establishedat room temperature through an interlaboratory study (4) involving six intern
41、ational laboratories, see also 13.1.3. The same verification specimens canalso be used to verify the absorbed energy scale of the impact machine in accordance with Test Methods E23 at either -40 C61 C or room temperature(21 C 6 1 C).6 If interested, email charpyboulder.nist.gov.FIG. 1 Allowable Erro
42、rs in Force MeasurementsE2298 13a37.2.7 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 supplied by NISTin Boulder, C
43、O as SRM 2112 (24 kN) and SRM 2113 (33 kN), and can also be used to verify the absorbed energy scale of theimpact machine in accordance with Test Methods E23 at -40 C 6 1 C (low and high energy specimens) and room temperature(21 C 6 1 C, super-high energy specimens). The certified Fm values have bee
44、n established at room temperature through aninterlaboratory study (4) involving six international laboratories, see also 13.1.3.7.3 Displacement Determination:7.3.1 Displacement is normally determined by converting a strain gage voltage-time measurement to a force-time measurement.The force-time rel
45、ationship 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 beginning of the deformation at t0, and expressing the velocity as a function oftime by v(t), the specimen bending displacement s(t)
46、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 may be calculated from:v05=2gh0 (3)where:g = the local acceleration due to gravity, andh0 = the falling height of the striker.7.
47、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 determine v0.7.3.3 Displacement can also be determined by non-contacting measurement of the displacement of the striker relative to t
48、heanvil using optical, inductive, or capacitive methods. The signal transfer characteristics of the displacement measurement systemmust correspond to that of the force measuring system in order to make the two recordings synchronous. The displacementmeasuring system shall be designed for nominal val
49、ues 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 acquisition requirement is a 10-bit analog-digital converter with a minimum sampling rate of 1000 datapoints per millisecond. Howev
