EN ISO 15630-3:2010

SLOVENSKI STANDARD
01-november-2011
1DGRPHãþD
SIST EN ISO 15630-3:2003
Jeklo za armiranje in prednapenjanje betona - Metode preskušanja - 3. del: Jeklo
za prednapenjanje (ISO 15630-3:2010)
Steel for the reinforcement and prestressing of concrete - Test methods - Part 3:
Prestressing steel (ISO 15630-3:2010)
Stähle für die Bewehrung und das Vorspannen von Beton - Prüfverfahren - Teil 3:
Spannstähle (ISO 15630-3:2010)
Aciers pour l'armature et la précontrainte du béton - Méthodes d'essai - Partie 3:
Armatures de précontrainte (ISO 15630-3:2010)
Ta slovenski standard je istoveten z: EN ISO 15630-3:2010
ICS:
77.140.15 Jekla za armiranje betona Steels for reinforcement of
concrete
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 15630-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2010
ICS 77.140.15 Supersedes EN ISO 15630-3:2002
English Version
Steel for the reinforcement and prestressing of concrete - Test
methods - Part 3: Prestressing steel (ISO 15630-3:2010)
Aciers pour l'armature et la précontrainte du béton - Stähle für die Bewehrung und das Vorspannen von Beton -
Méthodes d'essai - Partie 3: Armatures de précontrainte Prüfverfahren - Teil 3: Spannstähle (ISO 15630-3:2010)
(ISO 15630-3:2010)
This European Standard was approved by CEN on 14 October 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 15630-3:2010: E
worldwide for CEN national Members.

Contents Page
Foreword .3

Foreword
The text of ISO 15630-3:2010 has been prepared by Technical Committee ISO/TC 17 “Steel” of the
International Organization for Standardization (ISO) and has been taken over as EN ISO 15630-3:2010 by
Technical Committee ECISS/TC 104 “Concrete reinforcing and prestressing steels” the secretariat of which is
held by DIN.
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 2011, and conflicting national standards shall be withdrawn at the
latest by April 2011.
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.
This document supersedes EN ISO 15630-3:2002.
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 15630-3:2010 has been approved by CEN as a EN ISO 15630-3:2010 without any
modification.
INTERNATIONAL ISO
STANDARD 15630-3
Second edition
2010-10-15
Steel for the reinforcement and
prestressing of concrete — Test
methods —
Part 3:
Prestressing steel
Aciers pour l'armature et la précontrainte du béton — Méthodes
d'essai —
Partie 3: Aciers de précontrainte

Reference number
ISO 15630-3:2010(E)
©
ISO 2010
ISO 15630-3:2010(E)
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ii © ISO 2010 – All rights reserved

ISO 15630-3:2010(E)
Contents Page
Foreword .v
Introduction.vi
1 Scope.1
2 Normative references.1
3 Symbols.2
4 General provisions concerning test pieces.4
5 Tensile test.4
5.1 Test piece .4
5.2 Test equipment .4
5.3 Test procedure.4
5.3.1 General .4
5.3.2 Determination of the modulus of elasticity.5
6 Bend test .5
6.1 Test piece .5
6.2 Test equipment .6
6.3 Test procedure.6
6.4 Interpretation of test results.6
7 Reverse bend test.6
7.1 Test piece .6
7.2 Test equipment .7
7.3 Test procedure.7
8 Isothermal stress relaxation test .7
8.1 Principle of test.7
8.2 Test piece .8
8.3 Test equipment .8
8.3.1 Frame.8
8.3.2 Force-measuring device .8
8.3.3 Length-measuring device (extensometer).8
8.3.4 Anchoring device .8
8.3.5 Loading device .8
8.4 Test procedure.8
8.4.1 Provisions concerning the test piece.8
8.4.2 Application of force.9
8.4.3 Initial force .9
8.4.4 Force during the test.10
8.4.5 Maintenance of strain.10
8.4.6 Temperature.10
8.4.7 Frequency of force recording .10
8.4.8 Frequency of strain recording .10
8.4.9 Duration of the test.10
9 Axial force fatigue test.11
9.1 Principle of test.11
9.2 Test piece .11
9.3 Test equipment .11
9.4 Test procedure.12
9.4.1 Provisions concerning the test piece.12
9.4.2 Stability of force and frequency.12
ISO 15630-3:2010(E)
9.4.3 Counting of force cycles.12
9.4.4 Frequency.12
9.4.5 Temperature .12
9.4.6 Validity of the test.12
10 Stress corrosion test in a solution of thiocyanate .12
10.1 Principle of test.12
10.2 Sample and test piece .12
10.3 Test equipment .13
10.3.1 Frame .13
10.3.2 Force-measuring device .13
10.3.3 Time-measuring device.13
10.3.4 Cell containing the test solution .13
10.3.5 Test solution.13
10.4 Test procedure.14
10.4.1 Provisions concerning the test pieces.14
10.4.2 Application and maintenance of force.14
10.4.3 Filling of the cell.14
10.4.4 Temperature during the test .14
10.4.5 Termination of the test .14
10.4.6 Determination of median lifetime to fracture ( t ).15
f
11 Deflected tensile test.15
11.1 Principle of test.15
11.2 Sample and test piece .15
11.3 Test equipment .15
11.3.1 General description .15
11.3.2 Dimensions.15
11.3.3 Anchorages .16
11.3.4 Mandrel .16
11.3.5 Loading device.18
11.4 Test procedure.18
12 Chemical analysis.18
13 Measurement of the geometrical characteristics.18
13.1 Test piece .18
13.2 Test equipment .19
13.3 Test procedures.19
13.3.1 Rib measurements.19
13.3.2 Indentation measurements .20
13.3.3 Lay length of strand (P).20
13.3.4 Straightness .20
14 Determination of the relative rib area (f ).21
R
14.1 General.21
14.2 Calculation of f .21
R
14.2.1 Relative rib area .21
14.2.2 Simplified formulae.23
14.2.3 Formula used for the calculation of f .23
R
15 Determination of deviation from nominal mass per metre.23
15.1 Test piece .23
15.2 Accuracy of measurement.23
15.3 Test procedure.23
16 Test report .24
Bibliography .25

iv © ISO 2010 – All rights reserved

ISO 15630-3:2010(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 15630-3 was prepared by Technical Committee ISO/TC 17, Steel, Subcommittee SC 16, Steels for the
reinforcement and prestressing of concrete.
This second edition cancels and replaces the first edition (ISO 15630-3:2002), which has been technically
revised.
ISO 15630 consists of the following parts, under the general title Steel for the reinforcement and prestressing
of concrete — Test methods:
⎯ Part 1: Reinforcing bars, wire rod and wire
⎯ Part 2: Welded fabric
⎯ Part 3: Prestressing steel
ISO 15630-3:2010(E)
Introduction
The aim of ISO 15630 is to provide all relevant test methods for reinforcing and prestressing steels in one
standard. In that context, the existing International Standards for testing these products have been revised
and updated. Some further test methods have been added.
Reference is made to International Standards on the testing of metals, in general, as they are applicable.
Complementary provisions have been given if needed.

vi © ISO 2010 – All rights reserved

INTERNATIONAL STANDARD ISO 15630-3:2010(E)

Steel for the reinforcement and prestressing of concrete — Test
methods —
Part 3:
Prestressing steel
1 Scope
This part of ISO 15630 specifies test methods applicable to prestressing steels (bar, wire or strand) for
concrete.
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 4957, Tool steels
ISO 6508-1, Metallic materials — Rockwell hardness test — Part 1: Test method (scales A, B, C, D, E, F, G, H,
K, N, T)
ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
ISO 7500-1, Metallic materials — Verification of static uniaxial testing machines — Part 1: Tension/
compression testing machines — Verification and calibration of the force-measuring system
ISO 7801:1984, Metallic materials — Wire — Reverse bend test
ISO 9513, Metallic materials — Calibration of extensometers used in uniaxial testing
ISO 15630-3:2010(E)
3 Symbols
The symbols used in this part of ISO 15630 are given in Table 1.
Table 1 — Symbols
Symbol Unit Description Reference
a mm Rib height at the mid-point 13.3, 14.2
m
a mm Maximum height of rib or depth of indentation 13.3
max
a mm Average height of a portion i of a rib subdivided into p parts of length ∆l 14.2
s, i
a mm Rib height at the quarter-point 13.3, 14.2
1/4
a mm Rib height at the three-quarters point 13.3, 14.2
3/4
A % Percentage elongation after fracture 5.1, 5.3
A % Percentage total elongation at maximum force Clause 5
gt
b mm Width of transversal rib at the mid-point 13.3.1.6
c mm Rib or indentation spacing 13.3
C mm Groove width at nominal diameter of the mandrel, d , used for the deflected 11.3.4
a
tensile test
d mm Nominal diameter of the bar, wire or strand 5.3.1, 7.2, 9.2,
9.4.6, 10.3.4
d mm Nominal diameter of the mandrel used for the deflected tensile test 11.3.4
a
d mm Diameter with 2 gauge cylinders in the groove of the mandrel used for the 11.3.4
b
deflected tensile test
d mm Diameter of the gauge cylinder used for the deflected tensile test 11.3.4
e
d mm Diameter of guide hole 7.2
g
d mm Inner diameter of the groove of the mandrel used for the deflected tensile test 11.3.4
i
D % Average coefficient of reduction of the maximum force in the deflected tensile 11.2, 11.4
test
D mm Inner diameter of the cell in the stress corrosion test 10.3.4
c
D % Individual percentage of reduction of the maximum force in the deflected tensile 11.4
i
test
D mm Diameter of the mandrel of the bending device in the bend test 6.2.1
m
e mm Average gap between two adjacent ribs or indentation rows 13.3.1.4,
13.3.2.5
E MPa Modulus of elasticity 5.2, 5.3
f Hz Frequency of force cycles in the axial force fatigue test 9.1, 9.4.2
f — Relative rib area Clause 14
R
F N Individual breaking force in the deflected tensile test 11.4
a, i
F N Maximum force in the tensile test 5.3
m
F N Mean value of the maximum force 8.2, 10.2, 11.2,
m
11.4
F N 0,1 % proof force, non-proportional extension 5.2, 5.3
p0,1
F N 0,2 % proof force, non-proportional extension 5.2, 5.3
p0,2
F N Force range in the axial force fatigue test 9.1, 9.3, 9.4.2
r
2 © ISO 2010 – All rights reserved

ISO 15630-3:2010(E)
Table 1 (continued)
Symbol Unit Description Reference
F N Residual force in the test piece at time t in the relaxation test 8.1
rt
∆F N Force loss in the test piece at time t in the relaxation test 8.1
rt
F mm Area of longitudinal section of one rib 14.2
R
F N Upper force in the axial force fatigue test 9.1, 9.3, 9.4.2
up
F N Initial force in the isothermal stress relaxation test and the stress corrosion test 8.1, 8.2, 8.3, 8.4,
10.1, 10.2,
10.4.2
G mm Depth of the groove of the mandrel used for the deflected tensile test 11.3.4
h mm Distance from the top tangential plane of cylindrical supports to the bottom face 7.2
of the guide
h mm Bow height in the plane of the bow 13.3.4
b
l mm Length of indentation 13.3.2.4
L mm Length of the test piece in the stress corrosion test 10.2
t
L mm Gauge length (without force on the test piece) in the isothermal stress relaxation 8.1, 8.3, 8.4
test
10.2, 10.3.4,
Length of the test piece in contact with the solution in the stress corrosion test 10.4.1, 10.4.3,
10.4.5
∆L mm Elongation of the gauge length, L , under force, F , in the isothermal stress 8.1, 8.3, 8.4
0 0 0
relaxation test
L mm Length of the passive side in the deflected tensile test 11.3.2
L mm Length of the active side in the deflected tensile test 11.3.2
m, n — Coefficients or numbers 8.4.9, 13.3, 14.2
P mm Lay length of a strand 13.3.3
r mm Radius of cylindrical supports 7.2
R mm Radius at the base of the mandrel used for the deflected tensile test 11.3.4
Ra µm Surface roughness of the mandrel used for the deflected tensile test 11.3.4
S mm Nominal cross-sectional area of the test piece 5.3.2
n
t h Maximum agreed time for the stress corrosion test 10.4.5
a
t h Individual lifetime to fracture in the stress corrosion test 10.4.5
f, i
t h Median lifetime to fracture in the stress corrosion test 10.4.6
f
t s Starting time in the isothermal stress relaxation test and in the stress corrosion 8.4.2, 10.4
test
V mm Volume of test solution to fill the test cell in the stress corrosion test 10.4.3
Z % Percentage reduction of area 5.3.1
α ° Angle of deviation in the deflected tensile test 11.3.2
β ° Rib or indentation angle to the bar or wire axis 13.3
ε — Value of the strain for a force equal to x 5.3.2
x
ρ % Relaxation 8.4.9
e mm Part of the circumference without indentation or rib 13.3.1.4,
∑ i
13.3.2.5, 14.2
NOTE 1 MPa = 1 N/mm .
ISO 15630-3:2010(E)
4 General provisions concerning test pieces
Unless otherwise agreed or specified in the product standard, the pieces shall be taken from the finished
product normally before packaging.
Special care should be taken when sampling is made from the packaged product (e.g. coil or bundle), in order
to avoid plastic deformation which could change the properties of the samples used to provide the test pieces.
Specific complementary provisions concerning the test pieces may be indicated in the relevant clauses of this
part of ISO 15630, if applicable.
5 Tensile test
5.1 Test piece
In addition to the general provisions given in Clause 4, the free length of the test piece shall be sufficient for
the determination of the percentage total elongation at maximum force (A ) in accordance with 5.3.1.
gt
If the percentage elongation after fracture (A) is determined manually, the test piece shall be marked in
accordance with ISO 6892-1.
If the percentage total elongation at maximum force (A ) is determined by the manual method for bar or wire,
gt
equidistant marks shall be made on the free length of the test piece (see ISO 6892-1). The distance between
the marks shall be 20 mm, 10 mm or 5 mm, depending on the test piece diameter.
5.2 Test equipment
The test equipment shall be verified and calibrated in accordance with ISO 7500-1 and shall be at least of
class 1.
If an extensometer is used, it shall be of class 1 in accordance with ISO 9513 for the determination of E, F
p0,1
or F ; for the determination of A , a class 2 extensometer (see ISO 9513) may be used.

p0,2 gt
Grips shall be such as to avoid breaks in or very near the grips.
5.3 Test procedure
5.3.1 General
The tensile test for the determination of the modulus of elasticity (E), 0,1 % and 0,2 % proof force (F and
p0,1
F ), percentage total elongation at maximum force (A ) and/or percentage elongation after fracture (A) and
p0,2 gt
percentage reduction of area (Z) shall be carried out in accordance with ISO 6892-1.
An extensometer shall be used for the determination of the modulus of elasticity (E), 0,1 % and 0,2 % proof
force (F and F ) and percentage total elongation at maximum force (A ). The extensometer gauge
p0,1 p0,2 gt
length shall be as given in the relevant product standard.
Accurate values of A can only be obtained with an extensometer. If it is not possible to leave the
gt
extensometer on the test piece to fracture, the elongation may be measured as follows.
⎯ Continue loading until the extensometer records an elongation just greater than the elongation
corresponding to F , at which the extensometer is removed and the distance between the testing
p0,2
machine cross-heads is noted. The loading is continued until fracture occurs. The final distance between
the cross-heads is noted.
4 © ISO 2010 – All rights reserved

ISO 15630-3:2010(E)
⎯ The difference between the cross-head measurements is calculated as a percentage of the original
distance between the cross-heads and this value is added to the percentage obtained by an
extensometer.
For wire and bars, it is also permissible to determine A by the manual method (see ISO 6892-1).
gt
It is preferable to apply a preliminary force to the test piece, e.g. to about 10 % of the expected maximum
force before placing the extensometer.
1)
If A is not completely determined with an extensometer, this shall be indicated in the test report .
gt
Tensile properties, F , F , F , are recorded in force units.
p0,1 p0,2 m
For the determination of percentage elongation after fracture (A), the original gauge length shall be 8 times the
nominal diameter (d), unless otherwise specified in the relevant product standard. In case of dispute, A shall
be determined manually.
If the rupture occurs within a distance of 3 mm from the grips, the test shall, in principle, be considered as
invalid and it shall be permissible to carry out a retest. However, it shall be permitted to take into account the
test results if all values meet the relevant specified values.
5.3.2 Determination of the modulus of elasticity
The modulus of elasticity (E) shall be determined from the slope of the linear portion of the force-extension
diagram in the range between 0,2F and 0,7F , divided by the nominal cross-sectional area of the test piece
m m
(S ).
n
⎡⎤
E=−(0,7FF0,2 )/(εε− ) /S (1)
mm 0,7FF0,2 n
mm
⎣⎦
The slope may be calculated either by a linear regression of the measured data stored in a data storage
facility or by a best-fit visual technique over the above-defined portion of the registered curve.
In some special cases, e.g. hot-rolled and stretched bars, the above-mentioned method cannot be applied; a
secant modulus between 0,05F and 0,7F may then be determined as follows:
m m
⎡⎤
(0,7F−−0,05FS)/(εε ) /
mm0,7FF0,05 n
⎣⎦mm
In addition to the provisions given in 5.3.1, it shall be ensured that the stress rate shall not be changed within
the force range over which the modulus of elasticity is determined.
6 Bend test
6.1 Test piece
The general provisions given in Clause 4 apply.

1) For routine tests conducted by prestressing steel producers, the test information should be contained within internal
documentation.
ISO 15630-3:2010(E)
6.2 Test equipment
6.2.1 A bending device, the principle of which is shown in Figure 1, shall be used.
NOTE Figure 1 shows a configuration where the mandrel and support rotate and the carrier is locked. It is also
possible that the carrier rotates and the support or mandrel is locked.

Key
1 mandrel
2 support
3 carrier
Figure 1 — Principle of a bending device
6.2.2 The bend test may also be carried out by using a device with supports and a mandrel (e.g.
see ISO 7438).
6.3 Test procedure
The bend test shall be carried out at a temperature between 10 °C and 35 °C. The test piece shall be bent
over a mandrel.
The angle of bend and the diameter of the mandrel shall be in accordance with the relevant product standard.
6.4 Interpretation of test results
The interpretation of the bend test shall be carried out in accordance with the requirements of the relevant
product standard.
If these requirements are not specified, the absence of cracks visible to a person with normal or corrected
vision is considered as evidence that the test piece withstood the bend test.
A superficial ductile tear may occur at the base of the ribs or indentations and is not considered to be a failure.
The tear may be considered superficial when the depth of the tear is not greater than the width of the tear.
7 Reverse bend test
7.1 Test piece
In addition to the general provisions given in Clause 4, the test piece shall comply with ISO 7801.
6 © ISO 2010 – All rights reserved

ISO 15630-3:2010(E)
7.2 Test equipment
The test equipment shall comply with ISO 7801:1984, Clause 4.
For wire of nominal diameter 10 mm < d u 12,5 mm, the following conditions apply to the test equipment as
defined in ISO 7801: r = (30 ± 1) mm, h = 125 mm, d = 11 mm or 13 mm.
g
7.3 Test procedure
The reverse bend test shall be carried out in accordance with ISO 7801.
8 Isothermal stress relaxation test
8.1 Principle of test
The isothermal stress relaxation test consists of measuring, at a given temperature (generally fixed at 20 °C
unless otherwise agreed) the variations of force of a test piece maintained at constant length (L + ∆L ), from
0 0
an initial force (F ) (see Figure 2).
The loss in force is expressed as a percentage of the initial force for a given period of time.

Key
t time
L length
F force
Figure 2 — Principle of the isothermal stress relaxation test
ISO 15630-3:2010(E)
8.2 Test piece
The general provisions given in Clause 4 apply.
The test piece for the relaxation test shall be maintained in a straight condition. The free length of the test
piece between the grips shall not be subjected to any mechanical deformation or treatment of any kind.
Two test pieces adjacent to the test pieces for the stress relaxation test shall be taken for the determination of
the mean value of maximum force ( F m ), if the initial force, F , is expressed as a percentage of F m , e.g.
70 % × F .
m
8.3 Test equipment
8.3.1 Frame
Any deformation of the frame shall be within such limits that it does not influence the results of the test.
8.3.2 Force-measuring device
The force shall be measured either by a coaxial force cell or another appropriate device (e.g. lever loading
system).
The force cell shall be calibrated in accordance with ISO 7500-1 and have an accuracy of ±1 % for forces up
to 1 000 kN and ±2 % for forces greater than 1 000 kN.
Any other appropriate device shall provide the same accuracy as the one specified for the force cell.
−4
The resolution of the output of the force-measuring device shall be 5 × 10 F or better.
8.3.3 Length-measuring device (extensometer)
The gauge length (L ) shall be not less than 200 mm. For strands, it should preferably be 1 000 mm or an
integer number of the strand lay length where the actual length (L + ∆L ) is measured on the same wire of
0 0
the strand. The extensometer shall have an output or calibration of scale capable of a resolution of at least
−6
1 × 10 L or 1 µm, whichever is the greater.
8.3.4 Anchoring device
The anchoring device shall be constructed in such a way that slipping during the test either is not possible or
is corrected and rotation of the anchoring device is prevented.
8.3.5 Loading device
The loading device shall allow a smooth increase in loading the test piece without shock. It shall be
constructed in such a way that the length (L + ∆L ) can be maintained within the limits fixed in 8.4.5,
0 0
throughout the test, by reduction of force.
8.4 Test procedure
8.4.1 Provisions concerning the test piece
The test piece shall remain at least 24 h in the testing laboratory prior to the test.
The test piece shall be securely gripped in the anchorages of the test device in order to avoid any slip during
loading and during the test.
8 © ISO 2010 – All rights reserved

ISO 15630-3:2010(E)
8.4.2 Application of force
Application of force shall at all times be carried out smoothly and without shock.
The loading up to 20 % of the initial force, F , may be carried out as desired. Loading of the test piece from
20 % up to 80 % of F shall be applied continuously or in three or more uniform steps or with a uniform rate of
loading and shall be completed within 6 min. Application of the force between 80 % and 100 % of F shall be
continuous and shall be completed within 2 min, after achievement of 80 % of F .
−1
NOTE A rate of loading up to F of (200 ± 50) MPa⋅min is considered as a uniform rate of loading.
On attainment of the initial force, F , the force shall be kept constant for a period of 2 min. Immediately on
completion of this 2 min period, time, t , is established and recorded. Any subsequent adjustment of force
shall only be made in order to ensure that L + ∆L is kept constant.
0 0
The application of force is illustrated schematically in Figure 3.

Key
t time (min)
F/F ratio between the applied force and the initial force, F
0 0
Figure 3 — Application of force in the relaxation test
8.4.3 Initial force
The initial force, F , shall be as specified in the appropriate product standard. The measured value of the
initial force shall be within the tolerances of the specified value given in Table 2.
Table 2 — Tolerance of F
Value of F Tolerance of F
0 0
F u 1 000 kN ±1 %
F > 1 000 kN ±2 %
ISO 15630-3:2010(E)
8.4.4 Force during the test
At any time, the force shall not be permitted to exceed the initial force by more than the tolerances given in
Table 2.
8.4.5 Maintenance of strain
The strain imposed by the initial force, F , at time, t , shall be measured with a suitable mechanical, electrical
0 0
or optical extensometer having the precision defined in 8.3.3 at the selected initial gauge length, L . The
−6
variation of ∆L shall not exceed 5 × 10 L or 5 µm, whichever is the greater, during the force measurement
0 0
−6
and 7 × 10 L or 7 µm, whichever is the greater, between two consecutive force measurements.
8.4.6 Temperature
The temperature of the testing laboratory shall be such that the temperature of the test piece shall be
maintained within 20 °C ± 2 °C.
8.4.7 Frequency of force recording
The loss of force shall be continuously recorded or measured at least approximately at the standard time
intervals given in Table 3 after starting the test and then at least once per week.
Table 3 — Standard times of force recording
Minutes 1 2 4 8 15 30 60
Hours 2 4 6 24 48 96 120
8.4.8 Frequency of strain recording
The strain measured by the extensometer shall be recorded continuously, or at least during force
measurements, and twice between two consecutive force measurements (at equal time intervals).
8.4.9 Duration of the test
The duration of the test shall be not less than 120 h.
NOTE A common duration of a test is 120 h or 1 000 h.
The value of stress relaxation at 1 000 h (or more) may be extrapolated from tests terminating at not less than
120 h, where adequate evidence is p
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