ASTM E2298-09
(Test Method)Standard Test Method for Instrumented Impact Testing of Metallic Materials
Standard Test Method for Instrumented Impact Testing of Metallic Materials
SIGNIFICANCE AND USE
Instrumented impact testing provides an independent measurement of the total absorbed energy associated with fracturing CVN or MCVN specimens for test machines equipped with a dial and/or optical encoder.
Instrumented impact testing is particularly effective in MCVN testing since the resolution of a calibrated strain-gaged striker does not necessarily decrease with the magnitude of the measured energy.
In addition to providing an measure of total absorbed energy (Wt), instrumented testing enables the determination of characteristic force, energy, and displacement parameters. Depending on the material and test temperature, these parameters can provide very useful information (in addition to total absorbed energy) on the fracture behavior of materials such as: the temperature which corresponds to the onset of the lower shelf; the temperature which corresponds to the onset of the upper shelf; the pre-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 be used to highlight test results which should be discarded on the basis of misalignment or other critical test factors.
SCOPE
1.1 This standard establishes the requirements for performing instrumented Charpy V-Notch (CVN) and instrumented Miniaturized Charpy V-Notch (MCVN) impact tests on metallic materials. This method, which is based on experience developed testing 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 recording equipment such that similar sensitivity and comparable total absorbed energy measurements to those obtained in Test Methods E 23 and E 2248 are achieved.
1.2 The values stated in SI units are to be regarded as the standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: E2298 − 09
StandardTest Method for
Instrumented Impact Testing of Metallic Materials
This standard is issued under the fixed designation E2298; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 ISO Standard:
ISO 14556 Steel—Charpy V-notch Pendulum Impact
1.1 This standard establishes the requirements for perform-
Tests—Instrumented Test Method
ing instrumented Charpy V-Notch (CVN) and instrumented
Miniaturized Charpy V-Notch (MCVN) impact tests on metal-
3. Terminology
lic materials. This method, which is based on experience
3.1 Definitions—The symbols and definitions applicable to
developed testing steels, provides further information (in
instrumented impact testing are indicated in Table 1.
addition to the total absorbed energy) on the fracture behavior
of the tested materials. Minimum requirements are given for
4. Summary of Test Method
measurement and recording equipment such that similar sen-
4.1 This test method prescribes the requirements for instru-
sitivityandcomparabletotalabsorbedenergymeasurementsto
mented CVN and MCVN impact tests in accordance withTest
those obtained in Test Methods E23 and E2248 are achieved.
Methods E23 and E2248. The E23 and E2248 tests consist of
breaking by one blow from a swinging pendulum, under
1.2 The values stated in SI units are to be regarded as the
conditions defined hereafter, a specimen notched in the middle
standard.
and supported at each end. In order to establish the impact
1.3 This standard does not purport to address all of the
force-displacement diagram, it is necessary to instrument the
safety concerns, if any, associated with its use. It is the
strikerwithstraingages andmeasurethevoltageasafunction
responsibility of the user of this standard to establish appro-
of time during the impact event. The voltage-time curve is
priate safety and health practices and determine the applica-
converted to the force-time curve through a suitable static
bility of regulatory limitations prior to use.
calibration. The force-displacement relationship is then ob-
tained by double integration of the force-time curve. The area
2. Referenced Documents
under the force-displacement curve corresponds to the energy
absorbed by the specimen during the test.
2.1 ASTM Standards:
4.2 Force-displacement curves for different steels and dif-
A370Test Methods and Definitions for Mechanical Testing
ferent temperatures can vary even though the areas under the
of Steel Products
curves and the absorbed energies are identical. If the force-
E4Practices for Force Verification of Testing Machines
displacementcurvesaredividedintoanumberofcharacteristic
E23Test Methods for Notched Bar Impact Testing of Me-
parts, various phases of the test with characteristic forces,
tallic Materials
displacements, and energies can be deduced. These character-
E177Practice for Use of the Terms Precision and Bias in
istic values provide additional information about the fracture
ASTM Test Methods
behavior of the specimen.
E691Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
4.3 Application of instrumented test data to the evaluation
E2248Test Method for Impact Testing of Miniaturized
ofmaterialbehavioristheresponsibilityoftheuserofthistest
Charpy V-Notch Specimens
method.
5. Significance and Use
1 5.1 Instrumented impact testing provides an independent
This test method is under the jurisdiction of ASTM Committee E28 on
Mechanical Testing and is the direct responsibility of Subcommittee E28.07 on measurement of the total absorbed energy associated with
Impact Testing.
Current edition approved April 1, 2009. Published April 2009. DOI: 10.1520/
E2298-09. Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 4th Floor, New York, NY 10036, http://www.ansi.org.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Thistestmethodreferstostrikersinstrumentedwithstraingages.However,the
Standards volume information, refer to the standard’s Document Summary page on use of piezoelectric load cells or accelerometers is not excluded, provided their
the ASTM website. temperature sensitivity is properly accounted for.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2298 − 09
TABLE 1 Symbols and Designations Related to Instrumented
(i.e., 2 mm radius of striking edge) is allowed. Available data
Impact Testing 5
(1, 2) indicate that the influence of striker geometry on
Symbol Definition Unit
instrumented CVN forces is not very significant.
F Force at end of unstable crack propagation (arrest N
a
7.2 Force Measurement:
force)
F General yield force N 7.2.1 Force measurement is achieved by using an electronic
gy
F Maximum force N
m
sensor (piezoelectric load cell, strain gage load cell or a force
F Force at initiation of brittle fracture (unstable crack N
bf
measurement derived from an accelerometer).
propagation)
g Local acceleration due to gravity m/s
7.2.2 The force measuring system (including strain gages,
h Initial falling height of the striker m
wiring, and amplifier) shall have an upper frequency bound of
KV Absorbed energy measured from the machine dial or J
at least 100 kHz for CVN tests and 250 kHz for MCVN tests.
encoder
m Total effective mass of moving striker kg
For MCVN tests, if only absorbed energy has to be measured
s Displacement at end of unstable crack propagation m
a
from the curve, an upper frequency limit of 100 kHz is
(arrest force)
sufficient. The upper frequency bound for the system shall be
s Displacement at general yield m
gy
s Displacement at maximum force m
m verified by measurement or analysis. Measurements can be
s Displacement at initiation of brittle fracture m
bf
made using a function generator which is wired directly to the
s Displacement at end of force-displacement curve m
t
strain gage bridge.
t Time at the beginning of deformation of the specimen s
-1
v Initial striker impact velocity ms
0 7.2.3 Thesignalshallberecordedwithoutfiltering.Post-test
W Partial impact energy from F=0to F = F J
a a
filtering, however, is allowed.
W Partial impact energy from F=0to F = F J
bf bf
7.2.4 Calibration of the recorder and measurement system
W Partial impact energy from F=0to F = F J
m m
W Total impact energy J
t may be performed statically in accordance with the accuracy
requirements given below. It is recommended that the force
calibration be performed with the striker attached to the
pendulum assembly. The strain gage signal conditioning
fracturing CVN or MCVN specimens for test machines
equipment, cables, and recording device shall be used in the
equipped with a dial and/or optical encoder.
calibration. In most cases, a computer is used for data
5.2 Instrumented impact testing is particularly effective in
acquisition and the calibration shall be performed with the
MCVNtestingsincetheresolutionofacalibratedstrain-gaged
voltage read from the computer. The intent is to calibrate
striker does not necessarily decrease with the magnitude of the
throughtheelectronicsandcableswhichareusedduringactual
measured energy.
testing. Force is applied to the striker by using a suitable load
framewithaloadcellverifiedinaccordancewithPracticesE4.
5.3 In addition to providing an measure of total absorbed
7.2.4.1 The static linearity and hysteresis error of the
energy (W), instrumented testing enables the determination of
t
built-in, instrumented striker, including all parts of the mea-
characteristic force, energy, and displacement parameters.
surementsystemuptotherecordingapparatus(printer,plotter,
Depending on the material and test temperature, these param-
etc.), shall be within 62% of the recorded force, between 50
eters can provide very useful information (in addition to total
and100%ofthenominalforcerange,andwithin 61%ofthe
absorbedenergy)onthefracturebehaviorofmaterialssuchas:
full scale force value between 10 and 50% of the nominal
the temperature which corresponds to the onset of the lower
force range (see Fig. 1).
shelf; the temperature which corresponds to the onset of the
7.2.4.2 The instrumented striker system shall be calibrated
upper shelf; the pre-maximum force energy (W ); the post-
m
toensureaccurateforcereadingsareobtainedoverthenominal
maximum force energy; the energy associated with shear lip
force range which will be encountered in testing. The strain
tearing after brittle fracture; the general yield force (F ); the
gy
gaged system shall be designed to minimize its sensitivity to
forceatbrittlefractureinitiation(F );thearrestforce(F ).The
bf a
non-symmetric loading.
instrumented data may also be used to highlight test results
7.2.5 Calibration shall be performed if the instrumented
which should be discarded on the basis of misalignment or
striker has undergone dismantling or repair, unless it can be
other critical test factors.
shown that removal of the striker from the test machine, and
6. Precautions in Operation of the Machine subsequent reattachment to the machine, does not affect the
calibration. Calibration shall also be performed under the
6.1 Safety precautions should be taken to protect personnel
circumstances described below.
from electric shock, the swinging pendulum, flying broken
7.2.6 Requirements on Absorbed Energy—For each test in
specimens,andhazardsassociatedwithspecimenwarmingand
which the entire force signal has been recorded (i.e., until the
cooling media. See also 1.3.
force returns to the baseline), the difference between absorbed
energy given by the dial and/or optical encoder KV and the
7. Apparatus
total impact energy W shall be within 15% or 1 J, whichever
t
7.1 The test shall be carried out according to Test Methods
is larger. If this requirement is not met but the difference does
E23orE2248usingapendulumimpacttestingmachinewhich
not exceed 25% or 2 J, whichever is larger, force values shall
is instrumented to determine force-time or force-displacement
curves.
7.1.1 For instrumented CVN testing, the use of an instru-
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
mented striker conforming to the specifications of ISO 14556 this standard.
E2298 − 09
FIG. 1 Allowable Errors in Force Measurements
be adjusted until KV = W within 0.01 J (3). If the difference 7.3.2.1 Alternatively,thevelocitysignalregisteredwhenthe
t
exceeds 25% or 2 J, whichever is larger, the test shall be pendulum passes through its lowest position and strikes the
discarded and the user shall check and if necessary repeat the
specimen can be optically measured directly to determine v .
calibrationoftheinstrumentedstriker.Ifrecordingoftheentire
7.3.3 Displacement can also be determined by non-
force signal is not possible (for example due to the specimen
contacting measurement of the displacement of the striker
being ejected from the machine without being fully broken),
relative to the anvil using optical, inductive, or capacitive
the user shall demonstrate conformance to the requirements
methods. The signal transfer characteristics of the displace-
above by testing at least five Charpy specimens of any
mentmeasurementsystemmustcorrespondtothatoftheforce
equivalent material.
measuring system in order to make the two recordings syn-
7.3 Displacement Determination:
chronous. The displacement measuring system shall be de-
7.3.1 Displacement is normally determined by converting a
signed for nominal values of up to 30 mm. Linearity errors in
straingagevoltage-timemeasurementtoaforce-timemeasure-
the measuring system shall yield measured values to within
ment. The force-time relationship is proportional to the accel-
+2% in the range 1–30 mm. Measurements between zero and
erationasafunctionoftime.Givenanassumedrigidstrikerof
1 mm may not be sufficiently accurate to determine the
mass m, the initial impact velocity v , the time t following the
displacement. In such cases, it is recommended that the
beginning of the deformation at t , and expressing the velocity
displacement of the specimen be determined from time mea-
as a function of time by v(t), the specimen bending displace-
surement and the striker impact velocity as indicated in Eq 1
ment s(t) is calculated by double numerical integration as
and 2.
follows:
7.4 Recording Apparatus:
t
7.4.1 The minimum data acquisition requirement is a 10-bit
v t 5 v 2 F t dt (1)
~ ! * ~ !
m
analog-digitalconverterwithaminimumsamplingrateof1000
t
data points per millisecond. However, 12-bit or more is
t
recommended. A minimum storage capacity of 8000 data
points is required.
s t 5 v t dt (2)
~ ! * ~ !
7.4.2 The total absorbed energy measured using instrumen-
t
tation shall be compared with that shown by the machine dial
7.3.2 The initial impact velocity needed to perform the
(only for CVN testing), or preferably, by comparison with an
above integrations may be calculated from:
optical encoder (for both CVN and MCVN testing). If total
absorbed energy is measured using a machine dial or optical
v 5 =2gh (3)
0 0
encoder, then this data shall be reported along with the
where:
instrumented striker energy. For requirements on absorbed
g = the local acceleration due to gravity, and
energy based on the comparison between KV and W, refer to
t
h = the falling height of the striker.
7.2.6.
E2298 − 09
8. Test Specimens 10.3.5 The displacement at the end of the force-
displacement curve is s. This point is defined as the displace-
t
8.1 The CVN specimens shall be in accordance with Test
ment at which the force has decreased to the pre-test baseline
Method E23. The MCVN specimens shall be in accordance
value.
with Test Method E2248.
10.4 Characteristic Values of Impact Energy:
10.4.1 Given the force definitions in 10.1, the force-
9. Procedure
displacement curve may be partitioned and corresponding
9.1 Specimen Testing—The test is performed in the same
energies may be determined. The values of the partial impact
way as the CVN or MCVN impact test according to Test
energies are given the same subscript as the force at the end of
Methods E23 or E2248, respectively. In addition, the voltage-
the appropriate part of the force-displacement curve.
time curve is measured and evaluated to give the force-
10.4.2 The area under the complete force-displacement
displacementcurve.Theforce-displacementcurveisevaluated
curve up to s is the total
...
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