ASTM E467-98a(2004)
(Practice)Standard Practice for Verification of Constant Amplitude Dynamic Forces in an Axial Fatigue Testing System
Standard Practice for Verification of Constant Amplitude Dynamic Forces in an Axial Fatigue Testing System
SCOPE
1.1 This practice covers procedures for the dynamic verification of cyclic force amplitude measurement accuracy during constant amplitude testing in an axial fatigue testing system. It is based on the premise that force verification can be done with the use of a strain gaged elastic element. Use of this practice gives assurance that the accuracies of dynamic force readings from the test machine, at the time of the test, after any user applied correction factors, fall within the limits recommended in Section 9. It does not address static accuracy which must first be addressed using Practices E 4 or equivalent.
1.2 Verification is specific to a particular test machine configuration and specimen. This standard is recommended to be used for each configuration of testing machine and specimen. Where dynamic correction factors are to be applied to test machine force readings in order to meet the accuracy recommended in Section 9, the verification is also specific to the correction process used. Finally, if the correction process is triggered and/or performed by a person, then the verification is specific to that individual as well.
1.3 It is recognized that performance of a full verification for each configuration of testing machine and specimen configuration could be prohibitively time consuming and/or expensive. Annex A1 provides methods for estimating the dynamic accuracy impact of test machine and specimen configuration changes that may occur between full verifications. Where test machine dynamic accuracy is influenced by a person, estimating the dynamic accuracy impact of all individuals involved in the correction process is recommended. This practice does not specify how that assessment will be done due to the strong dependence on owner/operators of the test machine.
1.4 This practice is intended to be used periodically. Consistent results between verifications is expected. Failure to obtain consistent results between verifications using the same machine configuration implies uncertain accuracy for dynamic tests performed during that time period.
1.5 This practice addresses the accuracy of the testing machine's indicated forces as compared to a dynamometer's indicated dynamic forces. For the purposes of this verification, the dynamometer's indicated dynamic forces will be considered the true forces. Phase lag between dynamometer and force transducer indicated forces is not within the scope of this practice.
1.6 The results of either the Annex A1 calculation or the full experimental verification must be reported per Section 10 of this standard.
1.7 This standard does not address the issue of a test machine's control accuracy. It does not provide assurance that the force obtained equals the force commanded within the specified accuracy. The correlation being verified is between the test machine's indicated force and the true force on the test specimen as measured by a dynamometer.
1.8 This practice provides no assurance that the shape of the actual waveform conforms to the intended waveform within any specified tolerance.
1.9 This standard is principally focused at room temperature operation. It is believed there are additional issues that must be addressed when testing at high temperatures. At the present time, this standard practice must be viewed as only a partial solution for high temperature testing.
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Designation: E 467 – 98a (Reapproved 2004)
Standard Practice for
Verification of Constant Amplitude Dynamic Forces in an
Axial Fatigue Testing System
This standard is issued under the fixed designation E 467; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope machine configuration implies uncertain accuracy for dynamic
tests performed during that time period.
1.1 This practice covers procedures for the dynamic verifi-
1.5 This practice addresses the accuracy of the testing
cation of cyclic force amplitude measurement accuracy during
machine’s indicated forces as compared to a dynamometer’s
constant amplitude testing in an axial fatigue testing system. It
indicated dynamic forces. For the purposes of this verification,
is based on the premise that force verification can be done with
the dynamometer’s indicated dynamic forces will be consid-
the use of a strain gaged elastic element. Use of this practice
eredthetrueforces.Phaselagbetweendynamometerandforce
gives assurance that the accuracies of dynamic force readings
transducer indicated forces is not within the scope of this
from the test machine, at the time of the test, after any user
practice.
applied correction factors, fall within the limits recommended
1.6 The results of either theAnnexA1 calculation or the full
in Section 9. It does not address static accuracy which must
experimental verification must be reported per Section 10 of
first be addressed using Practices E 4 or equivalent.
this standard.
1.2 Verification is specific to a particular test machine
1.7 This standard does not address the issue of a test
configuration and specimen. This standard is recommended to
machine’s control accuracy. It does not provide assurance that
be used for each configuration of testing machine and speci-
the force obtained equals the force commanded within the
men.Wheredynamiccorrectionfactorsaretobeappliedtotest
specified accuracy. The correlation being verified is between
machine force readings in order to meet the accuracy recom-
the test machine’s indicated force and the true force on the test
mended in Section 9, the verification is also specific to the
specimen as measured by a dynamometer.
correction process used. Finally, if the correction process is
1.8 This practice provides no assurance that the shape of the
triggered and/or performed by a person, then the verification is
actual waveform conforms to the intended waveform within
specific to that individual as well.
any specified tolerance.
1.3 It is recognized that performance of a full verification
1.9 Thisstandardisprincipallyfocusedatroomtemperature
for each configuration of testing machine and specimen con-
operation. It is believed there are additional issues that must be
figuration could be prohibitively time consuming and/or ex-
addressed when testing at high temperatures. At the present
pensive. Annex A1 provides methods for estimating the dy-
time, this standard practice must be viewed as only a partial
namic accuracy impact of test machine and specimen
solution for high temperature testing.
configuration changes that may occur between full verifica-
tions. Where test machine dynamic accuracy is influenced by a
2. Referenced Documents
person, estimating the dynamic accuracy impact of all indi-
2.1 ASTM Standards:
viduals involved in the correction process is recommended.
E 4 Practices for Force Verification of Testing Machines
This practice does not specify how that assessment will be
E 6 Terminology Relating to Methods of Mechanical Test-
done due to the strong dependence on owner/operators of the
ing
test machine.
E 1823 Terminology Relating to Fatigue and Fracture Test-
1.4 This practice is intended to be used periodically. Con-
ing
sistent results between verifications is expected. Failure to
E 1942 Guide for Evaluating Data Acquisition Systems
obtain consistent results between verifications using the same
Used in Cyclic Fatigue and Fracture Mechanics Testing
This practice is under the jurisdiction ofASTM Committee E08 on Fatigue and
Fracture and is the direct responsibility of Subcommittee E08.03 on Advanced For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Apparatus and Techniques. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved May 1, 2004. Published June 2004. Originally Standards volume information, refer to the standard’s Document Summary page on
approved in 1972. Last previous edition approved in 1998 as E 467 – 98a. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 467 – 98a (2004)
2.2 Military Standard: 3.2.11 dynamometer force, n—the force value provided by
1312-B Fastener Test Methods the dynamometer’s readout.
2.3 ANSI Standard: 3.2.12 endlevel,n—eitheramaximumorminimumlevelfor
Z540-1-1994 Calibration Laboratories and Measuring and a cyclic waveform.
Test Equipment—General Requirements 3.2.13 fatigue testing system, n—for the purpose of this
2.4 NCSL Standard: practice, a device for applying repeated force cycles to a
Publication 940830/1600 NCSL Glossary of Metrology— specimenorcomponent,whichappliesrepeatedforcecyclesof
Related Terms the same span, frequency, waveshape, mean level, and endlev-
els.
3. Terminology
3.2.14 force command, n—the desired force to be applied to
the specimen or dynamometer by the testing machine.
3.1 Terminology used in this practice is in accordance with
3.2.15 force transducer, n—the test machine transducer
Terminology E 1823. Definitions provided in this practice are
which indicates the applied force by means of an electrical
considered either unfamiliar or not included in Terminology
voltage which can be measured.
E 1823.
3.2.15.1 Discussion—Typically the electrical voltage in-
3.2 Definitions:
creases linearly with applied force.The testing system may use
3.2.1 accuracy, n—for the purpose of this practice it shall
this voltage for control.
be defined as the degree of agreement between the indicated
3.2.16 indicated force, n—the force value provided by the
dynamic force (from the testing machine, after any necessary
force transducer or dynamometer’s readout (for example, a
corrections have been applied) and dynamic dynamometer
numeric or graphical output for reading by a human including
force (from the dynamometer instrumentation). The expected
a peak picking capability); these values are typically obtained
accuracy is defined in 9.1.
from a digital volt meter (DVM) or files generated by a
3.2.2 amplitude,n—one-halfthepeak-to-peakmeasurement
computerized data acquisition.
of the cyclic waveform.
3.2.17 instrumentation, n—the electronics used with a
3.2.3 cal factor, n—the conversion factor between the
transducerprovidingexcitationforthetransducer,conditioning
dynamometer force and the indicated force.
of the measured signal, and readout of that signal; typically the
3.2.4 conditioned force, n—the high level voltage or digital
conditioned signal is a voltage and the readout is a numerical
data available from the dynamometer or force transducer’s
display or printout.
signal conditioning instrumentation; it is frequently of value
3.2.18 peak, n—the maximum endlevel of a cycle.
during dynamic verification as it can be more conveniently
3.2.19 peak picking, n—the process of determining the peak
monitored by stand alone measurement instrumentation.
or valley of a cyclic waveform.
3.2.5 corrected force, n—the force obtained after applying a
3.2.20 repeatability, n—the closeness of agreement among
dynamic correction factor to the force transducer’s indicated
repeated measurements of the dynamic forces under the same
force.
conditions.
3.2.6 data acquisition equipment, n—the equipment used to
3.2.21 span, n—the absolute value of the peak minus the
convert a conditioned force to an indicated force.
valley for a cyclic waveform.
3.2.7 dynamic dynamometer forces, n—the maximum and
3.2.22 transducer, n—a measuring device which has an
minimum forces produced in the dynamometer during a
output signal proportional to the engineering quantity being
portion of a dynamic test.
measured.
3.2.8 dynamic errors, n—errors in the force transducer’s
3.2.23 true force, n—the actual force applied to the speci-
corrected force output that occur due to dynamic operation
men or dynamometer.
(with specimen bending errors intentionally corrected out).
3.2.24 valley, n—the minimum endlevel of a cycle.
3.2.9 dynamic indicated forces, n—the maximum and mini-
mum forces reported by the test machine during a portion of a
4. Significance and Use
dynamic test. These values are typically obtained using an
oscilloscope, peak-valley meter, or files generated by comput- 4.1 It is well understood how to measure the forces applied
erized data acquisition.
to a specimen under static conditions. Practices E 4 details the
3.2.10 dynamometer, n—an elastic calibration device used
required process for verifying the static force measurement
toindicatetheforcesappliedbyafatiguetestingsystemduring
capabilities of testing machines. During dynamic operation
dynamic operation. A strain gaged specimen is often used as
however, additional errors may manifest themselves in a
the dynamometer. Suitable transducer instrumentation is also
testing machine. Further verification is necessary to confirm
required to provide accurate readings over the intended fre-
the dynamic force measurement capabilities of testing ma-
quencyandforcerange.(RefertoPracticeE 467,AnnexA2for
chines.
detailed information about the dynamometer and instrumenta-
NOTE 1—ThestaticmachineverificationaccomplishedbyPracticesE 4
tion.)
simply establishes the reference. Indicated forces measured from the force
cell are compared with the dynamometer conditioned forces statically for
confirmation and then dynamically for dynamic verification of the fatigue
testing system’s force output.
Available from the U.S. Government Printing Office, Washington, DC 20402.
NOTE 2—The dynamic accuracy of the force cell’s output will not
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036. always meet the accuracy requirement of this standard without correction.
E 467 – 98a (2004)
Dynamic correction to the force cell output can be applied provided that
instrumentation for both the dynamometer and the machine
verification is performed after the correction has been applied.
beingverified.Calibrationofthedynamometerinstrumentation
NOTE 3—Overall test accuracy is a combination of measurement
must be current and traceable to the National Institute of
accuracy and control accuracy. This practice does not address control
Standards and Technology (NIST) or some other recognized
accuracy. It is up to the test operator to utilize appropriate measurement
national standards organization.
tools to confirm that the desired forces indicated forces meet the desired
5.3 Dynamometer Static Calibration—An absolute calibra-
forces within an acceptable degree of accuracy.
tion of the dynamometer as tested in accordance with Practices
4.2 Dynamic errors are primarily span dependent, not level
E 4 is not required. It is only necessary to statically calibrate
dependent. That is, the error for a particular force endlevel
the dynamometer indicated forces to the force transducer
during dynamic operation is dependent on the immediately
indicated forces at the force levels corresponding to the desired
preceding force endlevel. Larger spans imply larger absolute
dynamic force endlevels. It is this relationship that will be
errors for the same force endlevel.
verified under dynamic conditions to assure acceptable levels
4.3 Due to the many test machine factors that influence
of additional errors due to dynamic operation. Details of the
dynamic force accuracy, verification is recommended for every
static calibration of the dynamometer are included in Section 6
new combination of potential error producing factors. Primary
as an integral part of the practice.
factors are specimen design, machine configuration, test fre-
quency, and loading span. Clearly, performing a full verifica-
6. Procedure—Full Verification
tion for each configuration is often impractical. To address this
problem, dynamic verification is taken in two parts.
NOTE 6—The objective of a full verification is to show that the force
transducer corrected force accuracy is within an acceptable range when all
4.3.1 First, one or more full verifications are performed at
sources of dynamic error have been taken into account.
least annually. The main body of this practice describes that
procedure. This provides the most accurate estimate of dy-
6.1 Designing the Test—Prepare a matrix of configurations,
namic errors, as it will account for electronic as well as
test frequencies, and loading spans which address the follow-
acceleration-induced sources of error.
ing issues:
4.3.2 The second part, described in Annex A1, is a simpli-
6.1.1 Machine Configurations—Ideally, the machine should
fied verification procedure. It provides a simplified method of
be configured exactly as it will be used for material testing
estimating acceleration-induced errors only. This procedure is
including grips or fixturing, or both.Where it is not practical to
to be used for common configuration changes (that is,
test all expected configurations, test the configuration(s) with
specimen/grip/crosshead height changes).
the largest expected acceleration errors. In this case,AnnexA1
4.4 Dynamic verification of the fatigue system is recom-
must be used to verify additional test set-ups. It is recom-
mended over the entire range of force and frequency over
mended that at least two machine configurations be verified,
which the planned fatigue test series is to be performed.
and that the ability to detect acceleration errors against the true
Endlevels are limited to the machine’s verified static force as
errors measured with the full verifications be tested.
defined by the current static force verification when tested in
6.1.2 Test Frequencies—Where the testing machine will
accordance with Practices E 4.
only be used at a few discrete frequencies, perform the
verification at those frequencies. Where the machine will be
NOTE 4—There is uncertainty as to whether or not the vibration in a
frame will be different when operating in compression as opposed to
used at a variety of frequencies, the minimum and maximum
tension. As a consequence, this practice recommends performing verifi-
frequen
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