SIST EN ISO 26203-2:2012
(Main)Metallic materials - Tensile testing at high strain rates - Part 2: Servo-hydraulic and other test systems (ISO 26203-2:2011)
Metallic materials - Tensile testing at high strain rates - Part 2: Servo-hydraulic and other test systems (ISO 26203-2:2011)
This European Standard specifies the method for testing metallic sheet materials to determine the stress strain characteristics at high strain rate. This part of the standard covers the use of Servo-hydraulic and other test systems.
Metallische Werkstoffe - Zugversuch bei hohen Dehngeschwindigkeiten - Teil 2: Servohydraulische und andere Systeme (ISO 26203-2:2011)
Dieser Teil der ISO 26203 gilt für das Prüfen von Blechen aus metallischen Werkstoffen. Der Anwendungs-bereich erstreckt sich über einen Dehnratenbereich von 10–2 s–1 bis 103 s–1. Falls nicht anders festgelegt, können die Prüfungen zwischen 10 °C und 35 °C unter Anwendung einer servohydraulischen Prüfmaschine durchgeführt werden.
ANMERKUNG Messungen bei Dehnraten unter 10–2 s–1 können unter Anwendung von Prüfmaschinen für quasistatische Prüfungen durchgeführt werden.
ANMERKUNG Siehe ESIS P7 [1] und FAT Richtlinie [3] für andere Prüfgeometrien als in 6.1 und in Anhang B darge¬stellt.
Matériaux métalliques - Essai de traction à vitesses de déformation élevées - Partie 2: Systèmes d'essai servo-hydrauliques et autres systèmes d'essai (ISO 26203-2:2011)
L'ISO 26203-2:2011 spécifie les exigences pour les essais réalisés sur des matériaux métalliques. Seuls des exemples pour les essais sur des éprouvettes plates sont donnés; cependant, d'autres géométries peuvent être essayées. Le domaine d'application couvre une plage de vitesses de déformation comprise entre 10-2 s-1 et 103 s-1. Les essais doivent être réalisés, sauf spécification contraire, entre 10 °C et 35 °C, à l'aide d'un système d'essai de type servo-hydraulique.
Kovinski materiali - Natezno preskušanje pri velikih hitrostih deformacije - 2. del: Servohidravlični in drugi preskusni sistemi (ISO 26203-2:2011)
Ta del ISO 26203 podaja zahteve za preskušanje kovinskih materialov. Podani so samo primeri preskušanja ploščatih geometrij, preskušajo pa se lahko tudi druge geometrije. Področje uporabe obsega razpon nateznih hitrosti med 10-2 s-1 do 103 s-1. Preskusi se izvajajo pri temperaturi med 10 °C in 35 °C in, če ni navedeno drugače, z uporabo servohidravličnega preskusnega sistema.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 26203-2:2012
01-januar-2012
.RYLQVNLPDWHULDOL1DWH]QRSUHVNXãDQMHSULYHOLNLKKLWURVWLKGHIRUPDFLMHGHO
6HUYRKLGUDYOLþQLLQGUXJLSUHVNXVQLVLVWHPL ,62
Metallic materials - Tensile testing at high strain rates - Part 2: Servo-hydraulic and other
test systems (ISO 26203-2:2011)
Metallische Werkstoffe - Zugversuch bei hohen Dehngeschwindigkeiten - Teil 2:
Servohydraulische und andere Systeme (ISO 26203-2:2011)
Matériaux métalliques - Essai de traction à vitesses de déformation élevées - Partie 2:
Systèmes d'essai servo-hydrauliques et autres systèmes d'essai (ISO 26203-2:2011)
Ta slovenski standard je istoveten z: EN ISO 26203-2:2011
ICS:
77.040.10 Mehansko preskušanje kovin Mechanical testing of metals
SIST EN ISO 26203-2:2012 en,fr
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 26203-2:2012
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SIST EN ISO 26203-2:2012
EUROPEAN STANDARD
EN ISO 26203-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2011
ICS 77.040.10
English Version
Metallic materials - Tensile testing at high strain rates - Part 2:
Servo-hydraulic and other test systems (ISO 26203-2:2011)
Matériaux métalliques - Essai de traction à vitesses de Metallische Werkstoffe - Zugversuch bei hohen
déformation élevées - Partie 2: Systèmes d'essai servo- Dehngeschwindigkeiten - Teil 2: Servohydraulische und
hydrauliques et autres systèmes d'essai (ISO 26203- andere Systeme (ISO 26203-2:2011)
2:2011)
This European Standard was approved by CEN on 17 September 2011.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2011 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 26203-2:2011: E
worldwide for CEN national Members.
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SIST EN ISO 26203-2:2012
EN ISO 26203-2:2011 (E)
Contents Page
Foreword .3
2
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SIST EN ISO 26203-2:2012
EN ISO 26203-2:2011 (E)
Foreword
This document (EN ISO 26203-2:2011) has been prepared by Technical Committee ISO/TC 164 "Mechanical
testing of metals" in collaboration with Technical Committee ECISS/TC 101 “Test methods for steel (other
than chemical analysis)” the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by April 2012, and conflicting national standards shall be withdrawn at the
latest by April 2012.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 26203-2:2011 has been approved by CEN as a EN ISO 26203-2:2011 without any
modification.
3
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SIST EN ISO 26203-2:2012
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SIST EN ISO 26203-2:2012
INTERNATIONAL ISO
STANDARD 26203-2
First edition
2011-10-15
Metallic materials — Tensile testing at
high strain rates —
Part 2:
Servo-hydraulic and other test systems
Matériaux métalliques — Essai de traction à vitesses de déformation
élevées — Partie 2: Systèmes d’essai servo-hydrauliques et autres
systèmes d’essai
Reference number
ISO 26203-2:2011(E)
©
ISO 2011
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SIST EN ISO 26203-2:2012
ISO 26203-2:2011(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2011
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO’s
member body in the country of the requester.
ISO copyright office
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2011 – All rights reserved
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SIST EN ISO 26203-2:2012
ISO 26203-2:2011(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 1
5 Principle . 3
6 Apparatus . 3
7 Test pieces . 3
7.1 Test piece geometry . 3
7.2 Preparation of test pieces . 4
8 Procedure and measurements . 5
8.1 Velocity selection . 5
8.2 Force measurement . 5
8.3 Extension measurement . 6
8.4 Data acquisition . 6
9 Evaluation of tests . 6
9.1 Stress-strain curve . 6
9.2 Determination of key values . 7
9.3 Strain rates . 8
9.4 Determination of flow curves . 8
10 Test report . 9
Annex A (informative) Testing equipment .10
Annex B (informative) Examples of test piece geometries .12
Annex C (informative) Example of an engineering stress-strain curve .14
Bibliography .15
© ISO 2011 – All rights reserved iii
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SIST EN ISO 26203-2:2012
ISO 26203-2:2011(E)
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 through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International
Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 26203-2 was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals, Subcommittee
SC 1, Uniaxial testing.
ISO 26203 consists of the following parts, under the general title Metallic materials — Tensile testing at high
strain rates:
— Part 1: Elastic-bar-type systems
— Part 2: Servo-hydraulic and other test systems
iv © ISO 2011 – All rights reserved
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SIST EN ISO 26203-2:2012
ISO 26203-2:2011(E)
Introduction
The deformation behaviour of many technical materials shows a positive strain-rate effect up to ductile failure,
i.e. with increasing strain rate, an increase of yield stress and strain to failure can be observed. This information
is of great importance for the reliable assessment of crashworthiness of automobile structures, which is
increasingly determined by numerical methods to minimize the need for cost-intensive and time-consuming
crash tests. For the numerical simulation of crash-type loads, stress-strain curves determined at higher strain
rates are required. The quasi-static values determined according to ISO 6892-1, i.e. strain rates lower than or
−1
equal to 0,008 s ,are not suitable for the description of the behaviour of the material of a component under
dynamic load, i.e. at strain rates higher than those in quasi-static tests.
© ISO 2011 – All rights reserved v
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SIST EN ISO 26203-2:2012
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SIST EN ISO 26203-2:2012
INTERNATIONAL STANDARD ISO 26203-2:2011(E)
Metallic materials — Tensile testing at high strain rates —
Part 2:
Servo-hydraulic and other test systems
1 Scope
This part of ISO 26203 gives requirements for the testing of metallic materials. Only examples for testing flat
geometries are given; however, other geometries can be tested. The area of application spans a range of strain
−2 −1 3 −1
rates from 10 s to 10 s . Tests are carried out between 10 °C and 35 °C and, unless otherwise specified,
using a servo-hydraulic-type test system.
−2 −1
NOTE 1 Measurements at strain rates lower than 10 s can be performed using machines designed for quasi-static
testing.
NOTE 2 For test piece geometries other than those shown in 7.1 and Annex B, see ESIS P7 (Reference [1]) and
FAT Guideline (Reference [2]).
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced document
(including any amendments) applies.
ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 6892-1 apply.
4 Symbols
For the purposes of this document, the symbols given in ISO 6892-1 apply. Additional symbols, units and
descriptions are provided in Table 1.
Table 1 — Symbols
Symbol Unit Description
Test piece
a mm Original thickness of a flat test piece
o
b mm Original width of the parallel length of a flat test piece
o
b mm Width(s) of the clamping area of the test piece
k
L mm Original gauge length
o
L mm Parallel length
c
L mm Extensometer gauge length
e
r mm Transition radius
2
S mm Original cross-sectional area of the parallel length
o
2
S mm Dynamometer area: area on the fixed side of the test piece where only elastic
D
deformations are required during the test
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SIST EN ISO 26203-2:2012
ISO 26203-2:2011(E)
Table 1 (continued)
Symbol Unit Description
Time
t
s Time
t s Duration from beginning of test to moment of fracture initiation
f
Elongation
A % Percentage elongation after fracture
NOTE For non-proportional test pieces, the symbol A is supplemented by a subscript, which
shows the original gauge length, in millimetres, e.g. A = percentage elongation after fracture
20 mm
with an original gauge length L = 20 mm.
o
Extension
A % Percentage plastic extension at maximum force, F
g m
(plastic strain at maximum force, F )
m
A % Percentage total extension at maximum force, F
gt m
(total strain at maximum force, F )
m
Strain
e(t) % Time-dependent engineering strain
e % Plastic engineering strain
pl
e % Total engineering strain
t
ε True plastic strain
pl
ε True total strain
t
Rates
−1
v mm s Initial displacement rate
o
−1
e s Nominal engineering strain rate = v /L [Equation (1)]
o c
nom
−1
e s Mean engineering strain rate = A/t [Equation (4)]
f
mean
−1
e(t) s Time-dependent engineering strain rate = de(t)/dt
−1
e s Mean value of the time-dependent engineering strain rate: de(t)/dt in the range between
pl
start of yield or 1 % strain and strain at maximum force [Equation (5)]
f Hz Upper frequency limit of the relevant measuring system (force or extension)
u
Force
F N Maximum force
m
Engineering stress — True stress
a
R MPa Engineering stress
σ
MPa True stress
Yield strength — Proof strength — Tensile strength
R MPa Lower yield strength
eL
R MPa Proof strength, plastic extension
p
R MPa Tensile strength
m
Modulus of elasticity — Slope of stress-strain curve
E
MPa Modulus of elasticity
b
m MPa Slope of the elastic part of the stress-strain curve
E
a 2
1 MPa = 1 N/mm.
b
In the elastic part of the stress-strain curve the value of the slope can closely agree with the value of the modulus of elasticity if
optimal conditions (high resolution, double-sided averaging extensometers, proper alignment of the test piece, etc.) are used.
2 © ISO 2011 – All rights reserved
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SIST EN ISO 26203-2:2012
ISO 26203-2:2011(E)
5 Principle
The stress-strain characteristics of metallic materials at specific plastic strain rates are determined.
To perform tension tests at strain rates above those described in ISO 6892-1, the measurement of force and
elongation of the original gauge length, L, shall meet additional requirements in order to obtain reliable high-rate
o
stress-strain curves. This part of ISO 26203 describes the requirements for determining and evaluating the
3 −1
stress and strain in force equilibrium during plastic deformation at strain rates up to 10 s .
6 Apparatus
Testing machines in conformity with this part of ISO 26203 work on the principle that the kinetic energy required
for the test is applied on the impact (or loading) side of the test piece (see Figure A.1). The load cell is located
at the opposite end of the test piece, which is fixed or restrained in a clamp/grip (see Figure A.1). Loading at
high strain rates is preferably impact-like and, therefore, often does not allow a fixed coupling of the test piece
to the testing machine. All testing machines that permit a constant strain rate (within certain bounds; see 9.3)
during the entire test are suitable for testing.
The most common high-rate testing machine applicable to this part of ISO 26203 utilizes a servo-hydraulic
drive fitted with a slack adapter (see Reference [3]). Other systems, which may include, for example, flywheel
impactors and drop towers, may be used on condition that the requirements given in this part of ISO 26203
are met.
An axial-symmetric parallel alignment of the test pieces in the load train shall be verified in order to prevent
bending moments. The alignment of the load train elements may be performed in accordance with ASTM E1012
(see Reference [4]).
From a mechanical point of view, the load train should be compact and easy to manage. This enables the load
train to attain short acceleration times while also maintaining the natural frequency of the clamping and load
cell system at as high a level as possible.
7 Test pieces
7.1 Test piece geometry
Flat tensile test pieces are used for the dynamic testing of sheet materials. The strain rate developed in the test
piece gauge length is dependent on both the applied displacement rate and the parallel length of the reduced
section in the test piece. A test piece with a shorter parallel length enables higher strain rates. However, a
parallel length, L, shall be maintained so that the original gauge length, L, is in a state of uniaxial stress (see
c o
Figure 1). Therefore, the recommended sizes of the parallel length, L, the width, b, the thickness, a, and the
c o o
transition radius, r, for the test piece are as follows:
— L /b ≥ 2
o o
— L ≥ L +b /2
c o o
— b /a ≥ 2
o o
— b /b ≤ 0,5
o k
— r≥10 mm
Here b is the width of the clamping area.
k
Frequently used test piece dimensions based on ISO 6892-1 are given as examples in Annex B. Other
geometries of test pieces (e.g. ISO 26203-1, ESIS P7 and FAT guideline) may be applied if agreed upon
between the interested parties.
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SIST EN ISO 26203-2:2012
ISO 26203-2:2011(E)
Key
1 strain gauge
a original thickness
o
b original width of the parallel length
o
b width of the clamping area
k
L parallel length
c
L extensometer gauge length
e
L original gauge length
o
r transition radius
Figure 1 — Characteristic test piece dimensions
3 −1
NOTE In order to reach force equilibrium at low strain (beginning of the test) for high strain rates up to 10 s , it is
important to choose an appropriate length for the test piece.
The ends of the test pieces are designed to fit the available machine clamping devices. The dimensions of the
ends of the test pieces shall be designed such that only elastic deformation takes place within the sample ends
during the test.
Force measurement using strain gauges attached to the test piece (see Figure 1) requires a dynamometer
zone (see References [1] and [5]). The dynamometer zone is located at the fixed or restrained end of the test
piece. No plastic deformation is permissible in the dynamometer zone.
The test piece design should be validated prior to high-strain-rate testing. Validation can typically involve
conducting quasi-static tests on high rate test pieces within the strain rate limit permitted in ISO 6892-1. The
material properties derived from these tests should be compared with the data derived using the test piece
design, test procedure and test machine in accordance with ISO 6892-1.
7.2 Preparation of test pieces
The instructions and comments for the manufacture of flat tensile test pieces in ISO 6892-1:2009, Annex B,
shall be followed. In addition, special care should be taken to prevent strain hardening at the cut edges. Spark
erosion, water jet cutting, high-speed machining or other processes which mitigate the development of strain-
hardened edges, surface roughness and test piece distortion are recommended. The surfaces of the sheet
samples should remain in the original, as-received condition. The surface roughness of the cut edges shall be
minimized.
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SIST EN ISO 26203-2:2012
ISO 26203-2:2011(E)
8 Procedure and measurements
8.1 Velocity selection
The velocity of the actuator is selected prior to a high-strain-rate test to achieve the desired strain rate in the
parallel length of the test piece. An initial displacement rate of v permits the estimation of the achievable
o
nominal engineering strain rate using Equation (1):
e = v / L (1)
nom o c
where L is the parallel length of the test piece.
c
The strain rate recorded during a test deviates from the estimated value (see 9.3) due to the compliance in the
loading train.
NOTE For drop towers, the speed is determined by a calculation based on the drop height.
The material behaviour is governed by the strain rate in the parallel length of the test piece during the test.
Therefore, the purpose of the test procedure is to conduct a test with a constant strain rate in the parallel length
of the test piece (see 9.3) and not necessarily a constant velocity of the actuator.
8.2 Force measurement
The natural frequency of piezo-electric load cells is typically high enough for an accurate force measurement at
−1
lower strain rates. For strain rates greater than approximately 50 s , it is recommended that force be measured
either by strain gauges in a test piece area subjected to purely elastic deformation (dynamometer zone; see
Figure 1) or by means of a local dynamometer, such as a strain gauge placed on a grip (see References [2],
[6], [7] and [8]).
Spontaneous transfer of force into a test piece at high strain rate causes the test piece and parts of the
testing machine to oscillate increasingly as the displacement rate grows. These oscillations can be either of a
longitudinal or of a bending type. They are recorded as oscillations superposed to the force signal and thus in
the stress-strain curve. The inherent material deformation behaviour can be observed as phenomena similar
to “force oscillations” (discontinuous yielding associated with Lüders band propagation, dynamic strain ageing,
deformation twinning, etc,).
Prevention or at least reduction of oscillations in the force signal is an important criterion when selecting the
dynamometric procedure. In general, it can be ascertained that the further the force is measured outside the
gauge length and/or the higher the velocity of the actuator is, the greater are the oscillations.
It can be advantageous to apply a strain gauge on each side of the test piece to determine the proportion of
oscillations resulting from bending effects. Each signal is analysed separately in order to assess any bending
component. The use of damping elements in the load train in order to minimize oscillations should be carried
out with care. Damping reduces the strain rate at the beginning of the test, which in turn can influence the yield
strength.
Calibration of the dynamometer should be performed in a suitable manner. Test pieces fitted with strain gauges
can be calibrated quasi-statically. To this end, a test piece is subjected to a force, which corresponds to a
maximum of two thirds of the yield strength or proof stress in order to determine the calibration factor. Other
methods of force calibration are described in References [2], [9] and [10].
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SIST EN ISO 26203-2:2012
ISO 26203-2:2011(E)
−1
For tests at strain rates lower than 10 s , the upper frequency limit, f (−3dB) shall be at least 10 kHz. For
u
higher strain rates, Equation (2) applies according to ESIS P7 (see Reference [1]):
f ≥ 1 000×e (2)
u
where
f is the upper frequency limit of the force measuring system;
u
e is the strain rate.
8.3 Extension measurement
Different measuring systems are in use for reliable measurements of extension in the area of the original
gauge length. Usually, mechanical clip-on extensometers can be used up to strain rates of approximately
−1 −1
1 s . At strain rates higher than 1 s , the mechanical clip-on extensometers shall be replaced by inertia-free
measuring systems, e.g. strain gauges, electro-optical extensometers, laser measuring systems or high-speed
photography.
NOTE The determination of strain via actuator displacement, e.g. LVDT (linear variable differential transformer)
measurement or other measurements outside the original gauge length, L, is not recommended. These can only be
o
applied if the stiffness of the machine and its load train components have been taken into account appropriately.
It is desirable to carry out the entire test using only one measurement technique. If this is not possible, or if
higher measuring accuracy is required, a number of techniques may be combined. For tests within the range of
uniform strain, it is permissible to use an initial extensometer gauge length, L, shorter than the original gauge
e
length, L, if the homogeneity in material behaviour is sufficient. The true strain may also be recorded directly
o
by suitable measuring instruments.
Calibration of the measuring instrument for stroke/strain measurement shall be performed in a suitable manner.
−1
For tests at strain rate lower than 10 s , the frequency limit, f (−3dB), shall be at least 1 kHz. For higher strain
u
rates, Equation (3) (see Reference [1]) applies:
f ≥100×e (3)
u
where
f is the upper frequency limit of the extension measuring system;
u
e is the strain rate.
It is basically recommended that the percentage elongation after fracture be determined from markings placed
on the test piece before the test, as stated in ISO 6892-1. These markings shall be applied in such a way that
they have no effect on the deformation behaviour.
8.4 Data acquisition
The data pertaining to force and stroke/strain measurement are recorded with a sampling rate of at least four
times the limit frequency of the force measurement. These data are referred to as raw data and represent a
fundamental part of the test result. For subsequent evaluation, the number of data pairs may be reduced.
9 Evaluation of tests
9.1 Stress-strain curve
In a manner similar to the quasi-static tests in accordance with ISO 6892-1, force, extension and strain, as well
as the stress-strain curve, shall be determined.
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SIST EN ISO 26203-2:2012
ISO 26203-2:2011(E)
The stress-strain curve is calculated from the originally measured signals. For further evaluation, it is
advantageous to have a monotonically increasing strain signal for the duration of the test. If this is not possible
for technical reasons related to measurement (e.g. signal disturbance), a monotonic signal may be obtained
via different procedures, for example the application of a moving average procedure, the determination of a
polynomial approximation or a spline on a polynomial basis or a filter. If, however, other test-related factors are
responsible, such as a drop in speed, this may be applied to a limited extent only. I
...
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