ASTM E467-98a
(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 verification of constant-amplitude testing in an axial load fatigue testing system. Annex A1 provides methods for determining whether an actual experimental verification as described within this standard is required. The results of either the Annex calculation or the experimental verification must be reported as per Section 9 of this practice.
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Designation: E 467 – 98a
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 1.5 This practice addresses the accuracy of the testing
machine’s indicated forces as compared to a dynamometer’s
1.1 This practice covers procedures for the dynamic verifi-
indicated dynamic forces. For the purposes of this verification
cation of cyclic force amplitude measurement accuracy during
the dynamometer’s indicated dynamic forces will be consid-
constant amplitude testing in an axial fatigue testing system. It
ered the true forces. Phase lag between dynamometer and force
is based on the premise that force verification can be done with
transducer indicated forces is not within the scope of this
the use of a strain gaged elastic element. Use of this practice
practice.
gives assurance that the accuracies of dynamic force readings
1.6 The results of either the Annex A1 calculation or the full
from the test machine, at the time of the test, after any user
experimental verification must be reported per Section 10 of
applied correction factors, fall within the limits recommended
this standard.
in Section 9. It does not address static accuracy which must
1.7 This standard does not address the issue of a test
first be addressed using Practices E 4 or equivalent.
machine’s control accuracy. It does not provide assurance that
1.2 Verification is specific to a particular test machine
the force obtained equals the force commanded within the
configuration and specimen. This standard is recommended to
specified accuracy. The correlation being verified is between
be used for each configuration of testing machine and speci-
the test machine’s indicated force and the true force on the test
men. Where dynamic correction factors are to be applied to test
specimen as measured by a dynamometer.
machine force readings in order to meet the accuracy recom-
1.8 This practice provides no assurance that the shape of the
mended in Section 9, the verification is also specific to the
actual waveform conforms to the intended waveform within
correction process used. Finally, if the correction process is
any specified tolerance.
triggered and/or performed by a person, then the verification is
1.9 This standard is principally focused at room temperature
specific to that individual as well.
operation. It is believed there are additional issues that must be
1.3 It is recognized that performance of a full verification
addressed when testing at high temperatures. At the present
for each configuration of testing machine and specimen con-
time this standard practice must be viewed as only a partial
figuration could be prohibitively time consuming and/or ex-
solution for high temperature testing.
pensive. Annex A1 provides methods for estimating the dy-
namic accuracy impact of test machine and specimen
2. Referenced Documents
configuration changes that may occur between full verifica-
2.1 ASTM Standards:
tions. Where test machine dynamic accuracy is influenced by a
E 4 Practices for Force Verification of Testing Machines
person, estimating the dynamic accuracy impact of all indi-
E 6 Terminology Relating to Methods of Mechanical Test-
viduals involved in the correction process is recommended.
ing
This standard practice foes not specify how that assessment
E 1823 Standard Definitions of Terms Relating to Fatigue
will be done due to the strong dependence on owner/operators
and Fracture Mechanics Testing
of the test machine.
E 1942 Guide for Evaluating Data Acquisition Systems
1.4 This practice is intended to be used periodically. Con-
Used in Cyclic Fatigue Mechanics Testing
sistent results between verifications is expected. Failure to
2.2 Military Standards:
obtain consistent results between verifications using the same
1312-B Fastener Test Methods
machine configuration implies uncertain accuracy for dynamic
2.3 ANSI Standard:
tests performed during that time period.
Z540-1-1994 Calibration Laboratories and Measuring and
Test Equipment—General Requirements
This practice is under the jurisdiction of ASTM Committee E08 on Fatigue and
Fracture and is the direct responsibility of Subcommittee E08.03 on Advanced
Apparatus and Techniques. Annual Book of ASTM Standards, Vol 03.01.
Current edition approved Dec. 10, 1998. Published March 1999. Originally Available from the U.S. Government Printing Office, Washington, DC 20402.
published as E 467 – 72T. Last previous edition E 467 – 98. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 467 – 98a
2.4 NCSL Standard: specimen or component, which applies repeated force cycles of
Publication 940830/1600 NCSL Glossary of Metrology— the same span, frequency, waveshape, mean level, and endlev-
els.
Related Terms
3.2.14 force command, n—the desired force to be applied to
the specimen or dynamometer by the testing machine.
3. Terminology
3.2.15 force transducer, n—the test machine transducer
3.1 Terminology used in this practice is in accordance with
which indicates the applied force by means of an electrical
Terminology E 1823. Definitions provided herein are consid-
voltage which can be measured.
ered either unfamiliar or not included in Terminology E 1823.
3.2.15.1 Discussion—Typically the electrical voltage in-
3.2 Definitions:
creases linearly with applied force. The Testing System may
3.2.1 accuracy, n—for the purpose of this practice it shall
use this voltage for control.
be defined as the the degree of agreement between the
3.2.16 indicated force, n—the force value provided by the
indicated dynamic force (from the testing machine, after any
force transducer or dynamometer’s readout (for example, a
necessary corrections have been applied) and dynamic dyna-
numeric or graphical output for reading by a human including
mometer force (from the dynamometer instrumentation). The
a peak picking capability); these values are typically obtained
expected accuracy is defined in Section 9.1.
from a digital volt meter (DVM), or files generated by a
3.2.2 amplitude, n—one-half the peak-to-peak measurement
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
transducer providing excitation for the transducer, 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 an
3.2.22 transducer, n—a measuring device which has an
dminimum 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
4.1 It is well understood how to measure the forces applied
oscilloscope, peak-valley meter, or files generated by comput-
to a specimen under static conditions. Practices E 4 details the
erized data acquisition.
required process for verifying the static force measurement
3.2.10 dynamometer, n—an elastic calibration device used
capabilities of testing machines. During dynamic operation
to indicate the forces applied by a fatigue testing system during
however, additional errors may manifest themselves in a
dynamic operation. A strain gaged specimen is often used as
testing machine. Further verification is necessary to confirm
the dynamometer. Suitable transducer instrumentation is also
the dynamic force measurement capabilities of testing ma-
required to provide accurate readings over the intended fre-
chines.
quency and force range. (Refer to Practice E 467, Annex A2 for
detailed information about the dynamometer and instrumenta-
NOTE 1—The static machine verification accomplished by Practices E 4
tion.)
simply establishes the reference. Indicated forces measured from the force
cell are compared to the dynamometer conditioned forces statically for
3.2.11 dynamometer force, n—the force value provided by
confirmation and then dynamically for dynamic verification of the fatigue
the dynamometer’s readout.
testing system’s force output.
3.2.12 endlevel, n—either a maximum or minimum level for
NOTE 2—The dynamic accuracy of the force cell’s output will not
a cyclic waveform.
always meet the accuracy requirement of this standard without correction.
3.2.13 fatigue testing system, n—for the purpose of this
Dynamic correction to the force cell output can be applied provided that
practice, a device for applying repeated force cycles to a
verification is performed after the correction has been applied.
NOTE 3—Overall test accuracy is a combination of measurement
accuracy and control accuracy. This practice does not address control
accuracy. It is up to the test operator to utilize appropriate measurement
5 nd th
tools to confirm that the desired forces indicated forces meet the desired
Available from American National Standards Institute, 11 W. 42 St., 13
Floor, New York, NY 10036. forces within an acceptable degree of accuracy.
E 467 – 98a
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
NOTE 6—The objective of a full verification is to show that the force
problem, dynamic verification is taken in two parts.
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
6.1 Designing the Test—Prepare a matrix of configurations,
procedure. This provides the most accurate estimate of dy-
test frequencies, and loading spans which address the follow-
namic errors, as it will account for electronic as well as
ing issues:
acceleration induced sources of error.
6.1.1 Machine Configurations—Ideally, the machine should
4.3.2 The second part, described in Annex A1, is a simpli-
be configured exactly as it will be used for material testing
fied verification procedure. It provides a simplified method of
including grips or fixturing, or both. Where it is not practical to
estimating acceleration induced errors only. This procedure is
test all expected configurations, test the configuration(s) with
to be used for common configuration changes (that is,
the largest expected acceleration errors. In this case, Annex A1
specimen/grip/crosshead height changes).
must be used to verify additional test set-ups. It is recom-
4.4 Dynamic verification of the fatigue system is recom-
mended that at least two machine configurations be verified,
mended over the entire range of force and frequency over
and that the ability to detect acceleration errors against the true
which the planned fatigue test series is to be performed.
errors measured with the full verifications be tested.
Endlevels are limited to the machine’s verified static force as
6.1.2 Test Frequencies—Where the testing machine will
defined by the current static force verification when tested in
only be used at a few discrete frequencies, perform the
accordance with Practices E 4.
verification at those frequencies. Where the machine will be
NOTE 4—There is uncertainty as to whether or not the vibration in a used at a variety of frequencies, the minimum and maximum
frame will be different when operating in compression as opposed to
frequencies must be verified using the full verification proce-
tension. As a consequence this standard recommends performing verifi-
dure. Any operating frequency between those frequencies may
cations at maximum tension and maximum compression endlevels. The
be verified using Annex A1. A dynamic error graph may prove
total span does not need to be between those two levels, but can be
useful for identifying sources of dynamic errors and is recom-
performed as two tests.
mended though not required. See Annex A3 for an example.
NOTE 5—Primary el
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