EN ISO 26203-1:2010

SLOVENSKI STANDARD
01-maj-2011
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6LVWHP]HODVWLþQLPGURJRP,62
Metallic materials - Tensile testing at high strain rates - Part 1: Elastic-bar-type systems
(ISO 26203-1:2010)
Metallische Werkstoffe - Zugversuch bei hohen Dehngeschwindigkeiten - Teil 1:
Elastische Stoßwellentechnik (ISO 26203-1:2010)
Matériaux métalliques - Essai de traction à vitesses de déformation élevées - Partie 1:
Systèmes de type à barre élastique (ISO 26203-1:2010)
Ta slovenski standard je istoveten z: EN ISO 26203-1:2010
ICS:
77.040.10 Mehansko preskušanje kovin Mechanical testing of metals
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 26203-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
February 2010
ICS 77.040.10
English Version
Metallic materials - Tensile testing at high strain rates - Part 1:
Elastic-bar-type systems (ISO 26203-1:2010)
Matériaux métalliques - Essai de traction à vitesses de Metallische Werkstoffe - Zugversuch bei hohen
déformation élevées - Partie 1: Systèmes de type à barre Dehngeschwindigkeiten - Teil 1: Elastische
élastique (ISO 26203-1:2010) Stoßwellentechnik (ISO 26203-1:2010)
This European Standard was approved by CEN on 6 February 2010.

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 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 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
© 2010 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 26203-1:2010: E
worldwide for CEN national Members.

Contents Page
Foreword .3

Foreword
This document (EN ISO 26203-1:2010) 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 August 2010, and conflicting national standards shall be withdrawn at
the latest by August 2010.
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 26203-1:2010 has been approved by CEN as a EN ISO 26203-1:2010 without any
modification.
INTERNATIONAL ISO
STANDARD 26203-1
First edition
2010-02-15
Metallic materials — Tensile testing at
high strain rates —
Part 1:
Elastic-bar-type systems
Matériaux métalliques — Essai de traction à vitesses de déformation
élevées —
Partie 1: Systèmes de type à barre élastique

Reference number
ISO 26203-1:2010(E)
©
ISO 2010
ISO 26203-1:2010(E)
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ii © ISO 2010 – All rights reserved

ISO 26203-1:2010(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Principles.1
4 Terms and definitions .2
5 Symbols and designations.2
6 Apparatus.4
7 Test piece .5
7.1 Test-piece shape, size and preparation .5
7.2 Typical test piece.7
8 Calibration of the apparatus.8
8.1 General .8
8.2 Displacement measuring device.9
9 Procedure.9
9.1 General .9
9.2 Mounting the test piece .9
9.3 Applying force .9
9.4 Measuring and recording.9
10 Evaluation of the test result .11
11 Test report.12
Annex A (informative) Quasi-static tensile testing method.14
Annex B (informative) Example of one-bar method .16
Annex C (informative) Example of split Hopkinson bar (SHB) method.23
Bibliography.31

ISO 26203-1:2010(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 26203-1 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 2010 – All rights reserved

ISO 26203-1:2010(E)
Introduction
Tensile testing of metallic sheet materials at high strain rates is important to achieve a reliable analysis of
3 −1
vehicle crashworthiness. During a crash event, the maximum strain rate often reaches 10 s , at which the
strength of the material can be significantly higher than that under quasi-static loading conditions. Thus, the
reliability of crash simulation depends on the accuracy of the input data specifying the strain-rate sensitivity of
the materials.
Although there are several methods for high-strain rate testing, solutions for three significant problems are
required.
The first problem is the noise in the force measurement signal.
⎯ The test force is generally detected at a measurement point on the force measurement device that is
located some distance away from the test piece.
⎯ Furthermore, the elastic wave which has already passed the measurement point returns there by
reflection at the end of the force measurement device. If the testing time is comparable to the time for
wave propagation through the force measurement device, the stress-strain curve may have large
oscillations as a result of the superposition of the direct and indirect waves. In quasi-static testing,
contrarily, the testing time is sufficiently long to have multiple round-trips of the elastic wave. Thus, the
force reaches a saturated state and equilibrates at any point of the force measurement device.
⎯ There are two opposing solutions for this problem.
⎯ The first solution is to use a short force measurement device which will reach the saturated state
quickly. This approach is often adopted in the servo-hydraulic type system.
⎯ The second solution is to use a very long force measurement device which allows the completion of
a test before the reflected wave returns to the measurement point. The elastic-bar type system is
based on the latter approach.
The second problem is the need for rapid and accurate measurements of displacement or test piece
elongation.
⎯ Conventional extensometers are unsuitable because of their large inertia. Non-contact type methods such
as optical and laser devices should be adopted. It is also acceptable to measure displacements using the
theory of elastic wave propagation in a suitably-designed apparatus, examples of which are discussed in
this document.
⎯ The displacement of the bar end can be simply calculated from the same data as force measurement, i.e.
the strain history at a known position on the bar. Thus, no assessment of machine stiffness is required in
the elastic-bar-type system.
The last problem is the inhomogeneous section force distributed along the test piece.
⎯ In quasi-static testing, a test piece with a long parallel section and large fillets is recommended to achieve
a homogeneous uniaxial-stress state in the gauge section. In order to achieve a valid test with force
equilibrium during the dynamic test, the test piece must be designed differently from the typically
designed quasi-static test piece. Dynamic test pieces must generally be smaller in the dimension parallel
to the loading axis than the test pieces typically used for quasi-static testing.

ISO 26203-1:2010(E)
The elastic-bar-type system can thus provide solutions for dynamic testing problems and is widely used to
3 −1
obtain accurate stress-strain curves at around 10 s . The International Iron and Steel Institute developed the
“Recommendations for Dynamic Tensile Testing of Sheet Steel” based on the interlaboratory test conducted
by various laboratories. The interlaboratory test results show the high data quality obtained by the elastic-bar
type system. The developed knowledge on the elastic-bar-type system is summarized in this part of
ISO 26203; part 2 of ISO 26203 covers servo-hydraulic and other test systems used for high-strain-rate tensile
testing.
vi © ISO 2010 – All rights reserved

INTERNATIONAL STANDARD ISO 26203-1:2010(E)

Metallic materials — Tensile testing at high strain rates —
Part 1:
Elastic-bar-type systems
1 Scope
This International Standard specifies methods for testing metallic sheet materials to determine the
stress-strain characteristics at high strain rates. This part of ISO 26203 covers the use of elastic-bar-type
systems.
−3 3 −1
The strain-rate range between 10 to 10 s is considered to be the most relevant to vehicle crash events
based on experimental and numerical calculations such as the Finite Element Analysis (FEA) work for
crashworthiness.
In order to evaluate the crashworthiness of a vehicle with accuracy, reliable stress-strain characterization of
−3 −1
metallic materials at strain rates higher than 10 s is essential.
2 −1
This test method covers the strain-rate range above 10 s .
−1 −1
NOTE 1 At strain rates lower than 10 s , a quasi-static tensile testing machine that is specified in ISO 7500-1 and
ISO 6892-1 can be applied.
NOTE 2 This testing method may be applied to tensile test-piece geometries other than the flat test pieces considered
here.
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 Principles
The stress-strain characteristics of metallic materials at high strain rates are evaluated.
−1
At a strain rate higher than 10 s , the signal of the loading force is greatly perturbed by multiple passages of
waves reflected within the load cell that is used in the quasi-static test. Thus, special techniques are required
for force measurement. This may be accomplished in two opposite ways:
⎯ one is to lengthen the force measurement device in the loading direction, in order to finish the
measurement before the elastic wave is reflected back from the other end (elastic-bar type systems);
⎯ another way is to shorten the force measurement device, thus reducing the time needed to attain dynamic
equilibrium within the force measurement device and realizing its higher natural frequency
(servo-hydraulic type systems).
ISO 26203-1:2010(E)
−1 −1
Tests at low strain rates (under 10 s ) can be carried out using a quasi-static tensile testing machine.
However, special considerations are required when this machine is used for tests at strain rates higher than
conventional ones. It is necessary to use a test piece specified for high-strain-rate testing methods. Annex A
provides details of the test procedure for this practice.
4 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
4.1
elastic-bar-type system
measuring system in which the force-measuring device is lengthened in the axial direction to prevent force
measurement from being affected by waves reflected from the ends of the apparatus
NOTE The designation “elastic-bar-type system” comes from the fact that this type of system normally employs a
long elastic bar as force-measuring device.
5 Symbols and designations
Symbols and corresponding designations are given in Table 1.
Table 1 — Symbols and designations
Symbol Unit Designation
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 grip section of a test piece
g
L mm Original gauge length [see 7.1 e)]
o
L mm Parallel length
c
L mm Total length that includes the parallel length and the shoulders
total
L mm Final gauge length after fracture
u
r mm Radius of the shoulder
S mm Original cross-sectional area of the parallel length
o
S mm Cross-sectional area of the elastic bar
b
Time
t s Time
Elongation
Percentage elongation after fracture
NOTE With non-proportional test pieces, the symbol A is supplemented with an index which
A %
shows the basic initial measured length in millimetres, e.g. A = Percentage elongation after fracture
20mm
with an original gauge length L = 20 mm
o
A % Specified upper limit of percentage elongation for mean strain rate
u
2 © ISO 2010 – All rights reserved

ISO 26203-1:2010(E)
Table 1 (continued)
Symbol Unit Designation
Displacement
u mm Displacement by the elastic wave
u mm Displacement at the end of the original gauge length
u mm Displacement at the end of the original gauge length
u (t) mm Displacement of the end of the elastic bar at time t
B
Strain
e — Engineering strain
e — Desired engineering strain before achieving equilibrium
s
ε — Elastic strain
ε — Elastic strain at the end of the elastic bar (see Annex B)
B
ε — Elastic strain at section C (see Annex B)
g
Strain rate
−1
e s Engineering strain rate
−1

e s Mean engineering strain rate
Force
F N Force
F N Maximum force
m
Stress
R MPa Engineering stress
R MPa Tensile strength
m
R MPa Proof strength, total extension
t
Modulus of elasticity
E MPa Modulus of elasticity
E MPa Modulus of elasticity of the bar
b
Wave velociy
−1
c mm s Velocity of the wave propagation in the elastic bar
−1
c mm s Elastic wave propagation velocity in the test piece
Velocity
−1
v (t) mm s Velocity of the impact block (see Annex B)
A
−1
v mm s Particle velocity at any point in the bar (see Annex C)
−1
v mm s Incident particle velocity (see Annex C)
i
−1
v mm s Reflected particle velocity (see Annex C)
r
−1
v mm s Transmitted particle velocity (see Annex C)
t
ISO 26203-1:2010(E)
6 Apparatus
6.1 Elastic bar. By using a long elastic bar, the test should be finished before the elastic wave is reflected
back from the other end of the bar that is on the opposite side of the test piece. Consequently, the force can
be measured without being perturbed by the reflected waves. For this method, the one-bar testing machine
and the split Hopkinson bar (SHB) testing machine are normally used (see Annex B and Annex C).
6.2 Input device. For the input method, open-loop-type loading is normally applied. The upper limit of the
−1
input speed is approximately 20 m s . For the SHB testing machine, a striker tube or striker bar is used. For
the one-bar testing machine, a hammer is normally used.
6.3 Clamping mechanism. A proper clamping mechanism (a method for connecting a test piece and an
elastic bar) is critical to data quality (see Annex B and Annex C).
The clamping fixtures for the SHB or one-bar testing machines are mounted directly on the elastic bars. The
clamping fixtures should be of the same material and diameter as the elastic bars to ensure minimal
impedance change when the stress wave propagates through the loading train. If a different material or size is
used, proper consideration should be made in the evaluation of stress and strain.
6.4 Force measurement device. Force should be measured by strain gauges of a suitably short gauge
length, typically 2 mm, attached to elastic bars that are directly connected with the test piece.
The location of the strain gauges should be in an area where the elastic wave is not influenced by end effects.
In order to measure a one-dimensional elastic wave, the strain gauges shall be attached at a distance at least
five times the diameter of the bars from the ends of the bars (see Annex B and Annex C).
2 −1
NOTE The measurable strain-rate range by this method is 10 s or higher. It is impractical to construct a testing
2 −1
machine for strain rates below 10 s , because bar lengths of several tens of metres in length would be required.
To ensure the validity of stress-strain curves, the straightness of the elastic bars is crucial. Proper supports or
guides for the elastic bars are essential in achieving this.
6.5 Displacement measurement device. Strain in the tensile test is represented by the ratio between the
relative displacement between two points in the gauge section, e.g. the initial and final gauge lengths of the
test piece. Generally, in quasi-static testing, an extensometer attached to the gauge section of the test piece is
used and the measurement is accurate. However, at high strain rates, it is impossible to use this method due
to the inertia effects of the extensometer. Thus, displacement or test piece elongation measurement at high
strain rates shall use the non-contact type devices or strain gauges on elastic bars.
Measuring devices that can be utilized for measuring displacement in elastic-bar-type systems are described
3 −1
in 6.5.1 to 6.5.3. These devices are recommended for strain rates up to 10 s and measured displacements
should be recorded for the duration of the test. These devices may be used in combination. For example,
when devices 6.5.1 and 6.5.3 are used in combination, the displacement at one end of the original gauge
length (L ) is measured by the noncontact-type displacement gauge (6.5.1) and the other end is measured by
o
the strain gauge (6.5.3) that is attached on the surface of the bar.
6.5.1 Noncontact-type displacement gauge. The displacement at one end of the original gauge length
(L ) is measured and recorded by laser, optical or similar devices.
o
By using two 6.5.1 type devices or one 6.5.1 type device and one 6.5.3 type device, the variation of L in
total
Figure 1 (type-A test piece in Clause 7) with time can be measured and the elongation can be calculated.
6.5.2 Noncontact-type extensometer. High-speed cameras, Doppler or laser extensometers, or other
non-contact systems can be applied for measuring the variation of L in Figure 2 (type-B test piece in
c
Clause 7).
6.5.3 Strain gauge. The variation of displacement of the end of the elastic bar with time should be
calculated using Equation (1) which is based on the strain history measured by the strain gauge attached to
the elastic bar.
4 © ISO 2010 – All rights reserved

ISO 26203-1:2010(E)
t
ut() =c ε (t)dt (1)
B0 B
∫
where
u (t) is the displacement of the end of the elastic bar at time t;
B
ε is the elastic strain at the end of the elastic bar (see Annex B);

B
c is the velocity of the wave propagation in the elastic bar.

6.6 Data acquisition instruments. Amplifiers and data recorders such as oscilloscopes are used to assess
stress-strain curves from raw signals. Each instrument should have a sufficiently high frequency response.
The frequency response of all elements in the electronic measurement system must be selected to ensure
that all recorded data are not negatively influenced by the frequency response of any individual component;
typically this requires minimum frequency response on the order of 500 kHz. For digital data recorders, the
minimum resolution of measured data should be 10 bits.
7 Test piece
7.1 Test-piece shape, size and preparation
Test-piece geometry is determined by the following requirements.
a) The required maximum strain rate determines the parallel length. A test piece of shorter length can
achieve higher strain rates. In order to achieve force equilibrium in the test piece, the parallel length
should be short enough at a given strain-rate range.
3 −1
b) In order to assure equilibrium of forces at the strain rates up to 10 s , the preferred parallel length is
less than 20 mm.
Uniform deformation over the parallel length of the test piece requires that the force should be
equilibrated at both ends of the test piece. Force propagates as an elastic wave. To achieve equilibrium,
at least the following inequality should be satisfied.
L e
cs
u (2)

ce
where
L is the parallel length of the test piece;
c
c is the elastic wave propagation velocity in the test piece;
e is the desired engineering strain before achieving equilibrium;
s
e is the testing strain rate.
c) The width of the test piece should be determined to obtain uniaxial stress during the test. The following
rule should be applied:
L
o
W 2 (3)
b
o
ISO 26203-1:2010(E)
b
o
W 2 (4)
a
o
where
a is the original thickness of a flat test piece;

o
b is the original width of the parallel length of a flat test piece;
o
L is the original gauge length.
o
d) Generally, unless impractical or unnecessary, the thickness of the test piece should be the full thickness
of the material as far as testing capacity permits.
e) The radius at the shoulder of the type-A test piece (see Figure 1) should be small enough that L is
total
considered as the original gauge length (L ). The radius at the shoulder of the type-B test piece (see
o
Figure 2) should be large enough that L is considered as the original gauge length (L ).
c o
For type-A and type-B test pieces, uncertainties exist in uniaxial tensile data calculated from bar
displacement. These uncertainties result from the non-uniformity of axial strain within the original gauge
length, used here as the reference gauge length for strain calculations. To assess the potential effects of
strain non-uniformity, it is recommended that two sets of quasi-static true-stress versus true-strain data be
compared, i.e.
1) one obtained from strain measurements based on bar displacements (i.e. the displacements at the
bar-end positions on the test piece) and referenced to L or L for the selected high strain-rate test
total o
piece geometry, and
2) the other obtained from strain measurements with an extensometer mounted to the central part of the
parallel reduced section of a conventional tensile test piece conforming to ISO 6892-1.
The result of this comparison should be incorporated in the test report to provide an assessment to
potential users of high-strain-rate tensile data obtained with this specification. If the difference is outside
of a value agreed by the user and tester, then strain measurements based on local strain measurements
within the gauge length should be used.
f) The grip should have a much larger cross section than that of the parallel length of the test piece to
ensure negligible deformation and definitely no plastic deformation at the grip zone. Usually, because the
thicknesses of the grip and gauge length of the test piece are the same, the ratio of the grip and the
gauge length width shall comply with the following rule
bR
ot
< (5)
bR
gm
where
b is the original width of the parallel length of a flat test piece;
o
b is the width of the grip section of a test piece;
g
R is the tensile strength;
m
R is the proof strength, total extension.
t
g) Machined surface should be free of cold work, cracks, notches and other surface defects, which can
cause stress concentration.
6 © ISO 2010 – All rights reserved

ISO 26203-1:2010(E)
Key
b original width of the parallel length
o
b width of the grip section
g
L parallel length
c
L total length that includes the parallel length and the shoulders
total
r radius of the shoulder
Figure 1 — Type-A test piece
Key
b original width of the parallel length

o
b width of the grip section
g
L parallel length
c
r radius of the shoulder
Figure 2 — Type-B test piece
7.2 Typical test piece
Recommended dimensions of test pieces are shown in Figures 3 and 4. The ratio between the widths of the
grip and gauge section is normally above 2.
Based on the test methods and/or test purposes, other test piece configurations can be used.
The typical test pieces in Figures 3 and 4 are appropriate when the maximum measured strain rate is up to
3 −1
10 s and when the comparison of test results obtained at several strain rates is required. During uniform
elongation, the size effect of a test piece would be small. However, because after uniform elongation,
measured properties depend on the test-piece size, it is recommended that all test pieces used to obtain a
single data set should have the same geometry and dimensions, even for the low-strain-rate tests.
ISO 26203-1:2010(E)
Dimensions in millimetres
b
maximum 5
o
L
total
r 1,5
Figure 3 — Typical dimensions of a type-A test piece

Dimensions in millimetres
b maximum 5
o
L 10
c
r 5,0
Figure 4 — Typical dimensions of a type-B test piece
8 Calibration of the apparatus
8.1 General
The output of the strain gauge should be calibrated by applying a known static force to the strain gauged
elastic bar. Figure B.1 shows an example of the one-bar testing machine.
In the case of the SHB testing machine, stress and strain can be calculated by applying the theoretical
equation with the density, modulus of elasticity and the transmission speed of the longitudinal wave in the
elastic bar. In this case, it is necessary to carry out tests after precisely measuring each physical property and
ensuring its consistency. (Details are given in Annex C.)
8 © ISO 2010 – All rights reserved

ISO 26203-1:2010(E)
8.2 Displacement measuring device
For the displacement measuring devices, the appropriate calibration shall be carried out in the static condition.
9 Procedure
9.1 General
Using the input device (6.2), high speed strain is applied on the test piece along the axial direction of the test
piece. The force applied to the test piece is measured by the force measurement device (6.4). At the same
instance, the variation of L , L or L of the test piece is measured by the displacement measurement
total c o
device (6.5).
The configuration of the test piece should be determined based on the designated strain-rate range, the input
device (6.2), the force measurement device (6.4), and displacement measurement device (6.5).
The test is carried out at room temperature between 10 °C and 35 °C, unless otherwise specified. The test
temperature may be recorded if needed. Tests carried out under controlled conditions should be conducted at
a temperature of (23 ± 5)°C.
9.2 Mounting the test piece
When the test piece is mounted in the clamp, ensure good alignment to apply only axial force. Also the test
piece and the elastic bar should be connected carefully to ensure a good alignment.
When a type-A test piece is selected, the test piece should be mounted such that the spacing between grip
ends is L (see Figure 1) and the test-piece reduced-gauge section should be centred within this space (see
total
Figure C.3).
9.3 Applying force
Force is applied by the methods described in 6.2. To obtain the targeted strain rate, the velocity of the striker
tube, striker bar or hammer should be determined in advance.
NOTE Guidelines on the velocity of the hammer for the one-bar method and the velocity of the striker for the split
Hopkinson bar method are provided in B.2 and C.2, respectively.
9.4 Measuring and recording
The force measurement devices specified in 6.4 measure the time variation of elastic strain, and the
displacement measuring devices specified in 6.5 measure the time variation of the displacement of the
interfaces between the elastic bars and the test piece or of both end points of L . These measured data shall
o
be recorded.

a) Engineering strain and engineering strain rate (ee, )

Engineering strain (e) and engineering strain rate ( e ) should be calculated from displacement data
obtained following the technique outlined in 6.5. Engineering strain and engineering strain rate should be
calculated using the following equations.
eu=−()u/L (6)
12 0
ISO 26203-1:2010(E)
ee−
nn+1

e = (7)
∆t
where
u , u are displacements at the ends of the original gauge length;

1 2
e is the engineering strain at step n+1;
n+1
e is the engineering strain at step n;
n
∆t is time increment between steps n and n+1.
b) Engineering stress (R)
Using the force measured according to 6.4, the engineering stress is calculated by the following equation.
R = F/S (8)
o
where
R is the engineering stress;
F is the force;
S is the original cross-sectional area of the parallel length.
o
c) Percentage elongation after fracture (A)
Percentage elongation after fracture should be determined using the following equations as appropriate.
For a type-A test piece,
LL−
utotal
A = (9)
L
total
where
A is the percentage elongation after fracture;
L is the gauge length after fracture;
u
L is the original gauge length of a type-A test piece.
total
For a type-B test piece,
L − L
uc
A = (10)
L
c
where
A is the percentage elongation after fracture;
L is the gauge length after fracture;
u
L is the original gauge length of a type-B test piece.
c
10 © ISO 2010 – All rights reserved

ISO 26203-1:2010(E)

d) Mean strain rate ( e )
The mean value of the strain rate is obtained by averaging between strains of 1 % (0,01) and 10 % (0,1).
(0,1− 0,01)
e = (11)
tt−
10 1
where
−1

e is mean strain rate (s );
t is the time at a strain of 1 %;
t is the time at a strain of 10 %.
When the fracture strain is less than 10 %, calculate the mean strain rate between a strain of 1 % and the
measured fracture strain.
By agreement, the upper limit of strain range can be changed from 10 % to another specified value such
as the strain at the peak force.
When another specified value is applied as the upper limit of percentage elongation, the symbol should
be as follows

e
1− A
u
where A is the specified upper limit of percentage elongation for mean strain rate.
u
10 Evaluation of the test result
Due to problems in evaluation of material characteristics, a retest or a suitable interpretation of the test data
should be considered for the following cases:
a) the fracture of a test piece does not occur within a quarter distance of the gauge length from the centre of
the test piece;
b) the signal of stress has large oscillations (see Figure 5);
c) the mean strain rate is significantly different from the target strain rate and the initial rise in the strain rate
is not within the agreed strain range (e.g. 5 % of strain);
d) within the agreed strain range, the variation of strain rate exceeds ± 30 % of the mean strain rate;
e) the slope of the stress-strain curve in the elastic region in the dynamic condition is significantly different
from expected slope (irregular slope, Figure 5).
ISO 26203-1:2010(E)
Key
1 data without measurement problems
2 irregular slope
3 irregular slope + oscillation
R engineering stress (MPa)
e engineering strain
Figure 5 — Example of a measurement problem in a high-strain-rate test
There are two major quality issues for high-strain-rate tensile testing: 1) load oscillation; and 2) irregular slope
of the stress-strain curve in the elastic region.
The first issue is due to a problem in the force measurement system. Load oscillations appear when the test
machine, or elements in the load train, are not properly aligned (e.g. non-straight or misaligned elastic bar).
This can be remedied through a careful readjustment of the machine configuration and/or alignment of the
support or guides for the elastic bar.
The second issue concerns an irregular slope in the elastic region of the stress-strain curve. This can be due
to the addition of deformation in elements of the load train outside the gauge section of the test piece. This
problem is seldom seen in bar-type systems because the displacement of the bar end can be obtained using
the theory of elastic wave propagation. However, an irregular slope can appear when the mounting or
clamping strength between the test piece and the attachment (see Figures B.2 and B.3) is insufficient and/or
when the edge of the test piece (i.e. the edge of L ) is located at a position significantly different from the
total
bar end.
In such cases, the testing configuration should be adjusted.
11 Test report
By agreement between interested parties, the test report should contain items selected from the following:
a) reference to this part of ISO 26203;
b) specified materials, if known;
12 © ISO 2010 – All rights reserved

ISO 26203-1:2010(E)
c) test method (force-measuring method, displacement-measuring method, and type of load cell, etc.);
d) identification of test piece;
e) geometry and dimensions of sampling of test piece;
f) location and direction of test piece;
g) measured properties and results, i.e. stress-strain curve with strain rate, mean strain rate, maximum
tensile stress–strain, percent elongation after fracture, etc.
ISO 26203-1:2010(E)
Annex A
(informative)
Quasi-static tensile testing method
A.1 Scope
This annex explains the method to be used for determination of tensile properties of metallic materials using
−3 −1 −1 −1
strain-control within an approximate strain-rate range between 10 s and 10 s .
A.2 Input method/machine types
The testing machine used for causing strain shall be in conformity with ISO 7500-1. The grade of the testing
machine shall be subject to agreement between the parties concerned. For this test, a testing machine of the
electro-mechanical or servo-hydraulic type is usually used.
A.3 Clamping method
The testing machine shall be equipped with a clamp suitable for the test piece. The clamp shall be capable of
securely holding the test piece over the operation centreline of the tester throughout the test, and shall have a
construction that does not apply force other than tensile force.
A.4 Force measurement method
The force during the test is measured with a load cell usually comprising an electrical-resistance strain gauge
attached to an elastic body.
A.5 Displacement measurement
Depending on the shape of the test piece, L , L or L is measured.
o c total
Displacement during the test is measured by the travel of the crosshead or, preferably, with an extensometer
attached to the test piece.
In cases where the crosshead travel is measured, the resulting strain rate at the test piece may be lower than
strain rate determined from the crosshead travel, because the compliance of the testing machine is not
considered. An explanation is given in ISO 6892-1:2009, Annex F.
NOTE An extensometer of a type that uses a differential transformer, an optical extensometer or a strain gauge can
be used.
A.6 Test piece
Using same configurations of test pieces for high-strain-rate testing and quasi-static testing is recommended.
Depending on agreement between the parties concerned, however, a test piece of a different size may be
used.
14 © ISO 2010 – All rights reserved

ISO 26203-1:2010(E)
NOTE In the evaluation of automotive crash properties, material properties at different strain rates are required. For
consistent evaluation at all strain rates in the strain range, the use of identical test pieces is desirable.
A.7 Procedure
A.7.1 Test piece setup
Using a clamp suitable for the test piece with a particular geometry, it should be ensured that axial force only
is applied to the test piece throughout the test.
A.7.2 Straining
By feedback c
...