1、Designation: E 2298 09Standard Test Method forInstrumented Impact Testing of Metallic Materials1This standard is issued under the fixed designation E 2298; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、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 establishes the requirements for perform-ing instrumented Charpy V-Notch (CVN) and instrumentedMiniaturized Charpy V-No
3、tch (MCVN) impact tests on metal-lic 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 equip
4、ment such that similar sen-sitivity and comparable total absorbed energy measurements tothose obtained in Test Methods E23and E 2248 are achieved.1.2 The values stated in SI units are to be regarded as thestandard.1.3 This standard does not purport to address all of thesafety concerns, if any, assoc
5、iated 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:2A 370 Test Methods and Definitions for Mechanical Testingo
6、f Steel ProductsE4 Practices for Force Verification of Testing MachinesE23 Test Methods for Notched Bar Impact Testing ofMetallic MaterialsE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a T
7、est MethodE 2248 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 indicated in Table
8、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 E23and E 2248. The E23and E 2248 tests consistof breaking by one blow from a swinging pendulum, underconditions defined hereafter, a specimen notched
9、 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 through a s
10、uitable 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 Force-displacement curves for different steels and dif-fere
11、nt 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 energies can be deduced. These character
12、-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 Use5.1 Instrumented impact testing provides an independentm
13、easurement of the total absorbed energy associated withfracturing 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
14、decrease with the magnitude of themeasured energy.1This 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 April 1, 2009. Published April 2009.2For referenced ASTM standard
15、s, 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. 43rd St.,4th Floor, Ne
16、w 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.1Copyright ASTM International, 100 Barr Harbor Driv
17、e, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.3 In addition 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
18、-eters can provide very useful information (in addition to totalabsorbed energy) 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 po
19、st-maximum force energy; the energy associated with shear liptearing after brittle 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 m
20、isalignment orother 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 associated with specimen warming andcooling media. See also 1.3.7. Apparatus7
21、.1 The test shall be carried out according to Test MethodsE23 or E 2248 using a pendulum impact testing machinewhich is instrumented to determine force-time or force-displacement curves.7.1.1 For instrumented CVN testing, the use of an instru-mented striker conforming to the specifications of ISO 14
22、556(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 achieved by using an electronicsensor (piezoelectric load cell, strain gage load
23、 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 MCVN tests.For MCVN tests, if only absorbed energy has to be measuredfrom th
24、e curve, an upper frequency limit of 100 kHz issufficient. The upper frequency 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. P
25、ost-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 forcecalibration be performed with the striker attached to thependulum assembly. The strain g
26、age signal conditioning equip-ment, 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 the computer. The intent is to calibratethrough the electronics and cables which ar
27、e used during actualtesting. Force is applied to the striker by using a suitable loadframe with a load cell verified in accordance with PracticesE4.7.2.4.1 The static linearity and hysteresis error of thebuilt-in, instrumented striker, including all parts of the mea-surement system up to the recordi
28、ng 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 range (see Fig. 1).7.2.4.2 The instrumented striker system shall be calibratedto ensu
29、re 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.7.2.5 Calibration shall be performed if the instrumentedstriker has undergone dismantling or repair,
30、unless it can beshown that removal of 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 Absorbed EnergyFor each test inwhich the entire force s
31、ignal has been recorded (i.e., until theforce returns to the baseline), the 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
32、% or 2 J, whichever is larger, force values shallbe 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 of the instrumented striker. If recording of the entirefo
33、rce 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 material.5The boldface numbers in parentheses refer to the
34、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 (arrest force) NFgyGeneral yield force NFmMaximum force NFbfForce at initiation of brittle fracture (unstable crack p
35、ropagation) Ng Local acceleration due to gravity m/s2h0Initial falling height of the striker mKV Absorbed energy measured from the machine dial or encoder Jm Total effective mass of moving striker kgsaDisplacement at end of unstable crack propagation (arrest force) msgyDisplacement at general yield
36、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 impact energy fro
37、m F =0toF = FbfJWmPartial impact energy from F =0toF = FmJWtTotal impact energy JE22980927.3 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
38、-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 function of time by v(t), the specimen bending displace-ment s(t) is calculated by double numerical int
39、egration asfollows:vt! 5 v01mt*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 due to gravity, andh0= the falling height of the striker.7.3.2.1 Alternatively, the velocity signa
40、l 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 measurement of the displacement of the strikerrelative to the anvil using optical, inductive, or cap
41、acitivemethods. 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 displacement measuring system shall be de-signed for nominal values of up to 30 mm. Linearity errors
42、inthe measuring system shall yield measured values to within+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 st
43、riker impact velocity as indicated in Eq 1and 2.7.4 Recording Apparatus:7.4.1 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 datapo
44、ints is required.7.4.2 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 totalabsorbed energy is measured using a machine dial
45、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
46、 accordancewith Test Method E 2248.9. Procedure9.1 Specimen TestingThe test is performed in the sameway as the CVN or MCVN impact test according to TestMethods E23or E 2248, respectively. In addition, the voltage-time curve is measured and evaluated to give the force-displacement curve. The force-di
47、splacement curve is evaluatedwith respect to the characteristic phases of the deformation andfracture stages.9.2 Data AcquisitionThe high speed acquisition system(the portion of the system which is capable of storing thedynamic response signal) shall be triggered such that baselineFIG. 1 Allowable E
48、rrors in Force MeasurementsE2298093data before loading and after fracture (or release of thespecimen from the anvils) is retained in computer memory.10. Characteristics of the Force-Displacement Curve10.1 Type of Force-Displacement CurveRepresentativeforce-displacement curves and their characteristi
49、c force valuesare illustrated in Fig. 2.10.2 Characteristic Values of Force:10.2.1 The general yield force Fgyis the force at thetransition point from the initial linear elastic part, discardingthe inertia peaks (normally one, unless the specimen was notfully in contact with the anvils), to the curved increasing partof the force-displacement curve. It serves, to a first approxi-mation, as an indication of yielding across the entire ligament.10.2.2 The maximum force Fmcorresponds to the maximumvalue of the curve fitted through the oscillations of theforce-displacement cur
