ISO/TS 21913:2022
(Main)Temperature verification method applied to dynamic fatigue testing
Temperature verification method applied to dynamic fatigue testing
This document establishes verification procedures to determine the accuracy, speed of response, and stability of temperature measurement for materials testing equipment. These procedures are specified for the expected use in fatigue tests on metals where these characteristics are important to the fidelity of tests at high or varying temperature. The principles set out include sufficient provision for both contacting and non-contacting methods of temperature measurement. This document is for the end-to-end verification of registered value compared with “true” specimen temperature at the point of measurement. It cannot be used to specify the correct method or location of measurement. NOTE: The methodologies could be found applicable to test types beyond mechanical fatigue of metals, but that is outside the remit of this document.
Méthode de vérification de la température appliquée aux essais de fatigue dynamique
General Information
Standards Content (Sample)
TECHNICAL ISO/TS
SPECIFICATION 21913
First edition
2022-06
Temperature verification method
applied to dynamic fatigue testing
Méthode de vérification de la température appliquée aux essais de
fatigue dynamique
Reference number
© ISO 2022
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Measurement behaviour . 3
5 Representative verification equipment . 4
5.1 Reference measurements . . 4
5.2 Direct physically connected thermocouples (welded to specimen) . 5
5.3 Contacting thermocouples and other contacting devices not welded to specimen . 5
5.4 Non-contacting thermo-optical devices . 6
5.4.1 Constant emissivity coatings . 6
5.4.2 Native surfaces . 6
6 Basic isothermal verification methods . 6
6.1 Equipment set up . 6
6.2 Measurement of system resolution . 7
6.3 Summation of component bias errors . 7
6.4 Single point measurement of system bias error . 7
6.5 Multiple point assessment of resolution and bias error . 7
7 Evaluation of long term measurement drift . 8
7.1 Single point method (Post-test measurement) . 8
7.2 Time profile method (System assessment) . 8
8 Verification of dynamic temperature measurement . 8
8.1 Time lag . 8
8.1.1 Continuous ramp method . 8
8.1.2 Turning point method . 9
8.2 Stabilisation time . 9
9 Reporting . 9
Annex A (informative) Specific considerations for specimen temperature measurement
during fatigue tests .10
Bibliography .13
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
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URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 164, Mechanical Testing of Metals,
Subcommittee SC 05, Fatigue, fracture and toughness testing.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
It is the aim of this document to provide methodologies to verify the error in indicated measurement
relative to the actual temperature of the specimen test piece. Therefore, it is essential to account for all
factors, inclusive of environmental effects; not limiting the assessment to, for example, the performance
of a recording system and the thermoelectric coefficient of a batch of thermocouple wire.
Certain types of test and advanced simulation rely on accurately controlled and rapidly changing
temperature during the test, usually synchronised with control of mechanical loading. Within the scope
of this document, that would usually be a thermo-mechanical fatigue test.
Where temperature varies deliberately and rapidly during the test, it is appropriate to verify the degree
of time lag in system temperature reading. Without this evaluation (and implicitly a correction) then
either the apparent temperature accuracy or the phase accuracy may need to be unnecessarily reduced.
This document has been written with the intention of using congruent language and approach to that
[1] [2][3]
used for calibration of extensometers and verification of force measurement .
v
TECHNICAL SPECIFICATION ISO/TS 21913:2022(E)
Temperature verification method applied to dynamic
fatigue testing
1 Scope
This document establishes verification procedures to determine the accuracy, speed of response, and
stability of temperature measurement for materials testing equipment. These procedures are specified
for the expected use in fatigue tests on metals where these characteristics are important to the fidelity
of tests at high or varying temperature.
The principles set out include sufficient provision for both contacting and non-contacting methods of
temperature measurement.
This document is for the end-to-end verification of registered value compared with “true” specimen
temperature at the point of measurement. It cannot be used to specify the correct method or location of
measurement.
NOTE The methodologies could be found applicable to test types beyond mechanical fatigue of metals, but
that is outside the remit of this document.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply .
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
test system
equipment used to perform the (fatigue) test during which this temperature measurement is to be
utilised.
Note 1 to entry: This includes the gripping or fixtures, a representative specimen, the heating system (all parts
which influence the measurement), measurement conditioning device (e.g. thermocouple conditioning system),
data recording device and software.
Note 2 to entry: This verification is expected to take place on a complete test system, but it does not strictly
require the presence of the load frame provided that all parts influencing the specimen environment are held in
a representative configuration.
Note 3 to entry: The operating environment of the test system should be considered as part of the verification,
because changes in temperature of conditioning electronics can affect the measurement, especially if the cold
junction of a thermocouple or the detector array of a thermo-optical device is not at constant temperature.
Note 4 to entry: to entry:: Good laboratory conditions would typically be maintained by some form of climate
control, but that is not always possible and it does not guarantee to prevent local problems for specific
instruments.
3.2
representative specimen
test piece to be used in the verification process
Note 1 to entry: It should be of the same dimensions and material as the specimen(s) to be tested. In certain cases
this may be unfeasible so a very similar geometry to that expected in the final test schedule, with comparable
conductivity and emissivity should be used. Ideally, this would be an actual test specimen, but some deviation is
acceptable, provided it does not significantly affect the heat transfer characteristics of the system.
3.3
reference system
independent measurement system to be used to verify the test system (3.1)
Note 1 to entry: This should have a resolution at least 3 times smaller than that which will be published for the
verification (preferably more than 5 times) and should be traceable to a certified constant reference.
3.4
resolution
resolution of the temperature measurement system
fluctuation amplitude (half of the difference between maximum and minimum indicated values) of the
noise on the indicated temperature, over a period of 30 s or 30 consecutive readings at the intended
rate of data acquisition (whichever is larger)
Note 1 to entry: expressed in K or °C.
Note 2 to entry: Stated for specific temperature test point(s),or may be described as a function of indicated
temperature.
3.5
bias error
bias error of the temperature measurement system
difference between indicated temperature and reference measurement, for the mean average of values
measured over 30 s or 30 consecutive readings at the intended rate of data acquisition (whichever is
larger) at constant temperature
Note 1 to entry: expressed in K or °C.
Note 2 to entry: Alternatively, the average of values during one complete loading cycle may be used for slower
isothermal cycles, wh
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