Metallic materials — Steel — Method of test for the determination of brittle crack arrest toughness, Kca

This document specifies a test method for the determination of brittle crack arrest toughness. It is applicable to ferritic steel base metals exhibiting ductile to brittle transition behaviour. Applicable materials are rolled steel plates. It is intended for materials with a tensile strength of 950 MPa or less and a test piece thickness of 200 mm or less. The range of arrest temperatures is between −196 °C and +100 °C. This document can be applied to flat rolled steel plates but not to flattened steel pipes because the flattening can cause changes in arrest toughness.

Matériaux métalliques — Acier — Méthode d'essai pour déterminer la ténacité à la rupture fragile, Kca

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Published
Publication Date
21-Jul-2019
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6060 - International Standard published
Start Date
22-Jul-2019
Completion Date
22-Jul-2019
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ISO 20064:2019 - Metallic materials -- Steel -- Method of test for the determination of brittle crack arrest toughness, Kca
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INTERNATIONAL ISO
STANDARD 20064
First edition
2019-07
Metallic materials — Steel — Method
of test for the determination of
brittle crack arrest toughness, K
Matériaux métalliques — Acier — Méthode d'essai pour déterminer
la ténacité à la rupture fragile, K
Reference number
ISO 20064:2019(E)
ISO 2019
---------------------- Page: 1 ----------------------
ISO 20064:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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Published in Switzerland
ii © ISO 2019 – All rights reserved
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ISO 20064:2019(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols .......................................................................................................................................................................................................................... 2

5 Test equipment....................................................................................................................................................................................................... 3

5.1 General ........................................................................................................................................................................................................... 3

5.2 Testing machine ..................................................................................................................................................................................... 3

5.2.1 Force implementation ................................................................................................................................................. 3

5.2.2 Calibration of the load cell ....................................................................................................................................... 3

5.2.3 Force measurement ....................................................................................................................................................... 4

5.2.4 Method for force transfer to integrated test piece .............................................................................. 4

5.2.5 Loading direction ............................................................................................................................................................ 4

5.2.6 Distance between the loading pins .................................................................................................................. 4

5.3 Impact equipment ................................................................................................................................................................................ 4

5.3.1 Impact methods ................................................................................................................................................................ 4

5.3.2 Impact energy calculation........................................................................................................................................ 6

5.3.3 Reaction force receivers ............................................................................................................................................ 6

6 Test pieces ................................................................................................................................................................................................................... 7

6.1 Test piece configurations ............................................................................................................................................................... 7

6.2 Configurations of extension plates and tab plates ................................................................................................... 9

6.2.1 General...................................................................................................................................................................................... 9

6.2.2 Extension plates ............................................................................................................................................................11

6.2.3 Tab plates ............................................................................................................................................................................11

6.3 Welding of test piece and extension plates ..................................................................................................................11

7 Test methods ..........................................................................................................................................................................................................12

7.1 Temperature control method ..................................................................................................................................................12

7.1.1 Determination of temperature gradient ...................................................................................................12

7.1.2 Method of temperature control and monitoring ...............................................................................13

7.2 Crack initiation methods .............................................................................................................................................................14

8 Test procedures ..................................................................................................................................................................................................15

8.1 Pretest procedures ...........................................................................................................................................................................15

8.2 Impacting procedures ....................................................................................................................................................................16

8.3 Post-test operations ......... ................................................................................................................................................................16

8.4 Observation of fracture surfaces ..........................................................................................................................................17

9 Determination of arrest toughness ................................................................................................................................................22

9.1 Validation of arrested crack ......................................................................................................................................................22

9.2 Assessment of impact energy ..................................................................................................................................................23

9.3 Calculation of arrest toughness .............................................................................................................................................24

10 Reporting ...................................................................................................................................................................................................................24

Annex A (informative) Devices and method for controlling and monitoring the temperature

of test pieces ...........................................................................................................................................................................................................28

Annex B (normative) Method for obtaining K at a specific temperature ................................................................31

Annex C (normative) Calculation of stress intensity factors for a curved crack ..................................................33

Annex D (informative) Double tension type arrest test .................................................................................................................34

Annex E (informative) Duplex type arrest test ........................................................................................................................................37

© ISO 2019 – All rights reserved iii
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ISO 20064:2019(E)

Annex F (informative) Dynamic measurement methods .............................................................................................................40

Bibliography .............................................................................................................................................................................................................................44

iv © ISO 2019 – All rights reserved
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ISO 20064:2019(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.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso

.org/iso/foreword .html.

This document was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals,

Subcommittee SC 4, Fatigue, fracture and toughness testing.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
© ISO 2019 – All rights reserved v
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ISO 20064:2019(E)
Introduction

This document provides a test method for determining the crack arrest toughness of steels. Experimental

[2]

methods of crack propagation and arrest are documented in Reference [1] Among these, ASTM E1221

is a test method to evaluate lower bound crack arrest toughness, K , under plane strain conditions. On

[3]

the other hand, crack arrest testing methods using wide plates were developed in the 1950s and have

[3] [4][5][6]

been used for assessing the crack arrest capabilities of cryogenic tanks and pressure vessels .

In recent years, these methods have been extensively used for evaluating the crack arrest toughness of

[7]
ship steels .

The wide plate crack arrest test is intended to evaluate the arrest toughness, K , of steel plate at

its thickness of actual use and not the lower bound arrest toughness, K . However, the relationship

[4][6]

between the two arrest toughness values has been investigated . It was shown that K and

K values agreed at lower bound of K . Moreover, the wide plate crack arrest tests were shown to

ca ca

evaluate the arrest toughness at a higher temperature range at which K evaluation is impossible. The

theoretical background of crack arrest toughness testing with a temperature gradient is described in

References [8] and [9].

This document provides a test method for the determination of brittle crack arrest toughness of steel

by using wide plates with a temperature gradient.

The test method can be summarized as follows: after setting a temperature gradient across the width

of a test piece and applying uniform stress to the test piece, the test piece is struck to initiate a brittle

crack from a mechanical notch in either edge of the test piece and cause crack arrest after propagating

in the width direction (temperature gradient type arrest testing). Annex A describes typical devices

and a method of setting the temperature gradient on the piece. Using the stress intensity factor, the

arrest toughness, K , is calculated from the applied stress and the arrest crack length. This value is

the arrest toughness at the temperature at the point of crack arrest (arrest temperature). To determine

K at a specific temperature, such as the design temperature of a structure, the method specified in

Annex B is applicable.

The method described in Annex C can be used to determine the stress intensity factor for a curved

crack, in order to check the validity of a crack propagation path.

As a method for initiating a brittle crack, a secondary loading mechanism can be used (see Annex D).

The arrest characteristics of the test piece can also be evaluated by welding a crack starter plate to the

test plate in the width direction to enable a brittle crack initiated from the mechanical notch at the edge

of the test piece to propagate in the crack running plate and observing the propagation behaviour of the

crack immediately after entering the test plate (see Annex E).

The method explained in Annex F can be used to determine the dynamic behaviour of crack propagation

and measure the dynamic strain of a test piece.
vi © ISO 2019 – All rights reserved
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INTERNATIONAL STANDARD ISO 20064:2019(E)
Metallic materials — Steel — Method of test for the
determination of brittle crack arrest toughness, K
1 Scope

This document specifies a test method for the determination of brittle crack arrest toughness.

It is applicable to ferritic steel base metals exhibiting ductile to brittle transition behaviour. Applicable

materials are rolled steel plates. It is intended for materials with a tensile strength of 950 MPa or less

and a test piece thickness of 200 mm or less. The range of arrest temperatures is between −196 °C and

+100 °C. This document can be applied to flat rolled steel plates but not to flattened steel pipes because

the flattening can cause changes in arrest toughness.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements 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 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:

Tension/compression testing machines — Calibration and verification of the force-measuring system

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:/ /www. iso. org/obp
— IEC Electropedia: available at http:/ /www.e lectropedia. org/
3.1
brittle fracture
fracture with predominantly cleavage
3.2
arrest
sudden halt of a propagating brittle crack (3.4)
3.3
arrest toughness

materials resistance against brittle crack (3.4) propagation expressed in terms of stress intensity factor

3.4
brittle crack

crack propagating at approximately 300 m/s or more due to a brittle fracture (3.1)

3.5
arrest temperature

temperature at the point where a brittle crack (3.4) is arrested in the temperature gradient type arrest

toughness (3.3) test
© ISO 2019 – All rights reserved 1
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ISO 20064:2019(E)
3.6
test piece
flat steel plate in which arrest toughness (3.3) is to be evaluated
3.7
tab plate
thick end inserted for transferring force from a testing machine
3.8
extension plate
flat plate welded between the test piece (3.6) and tab plates (3.7)
3.9
integrated test piece
weld assembly of test piece (3.6), extension plates (3.8) and tab plates (3.7)
3.10
loading pin

pin used for the transfer of the force from the testing machine into the integrated test piece (3.9)

3.11
distance between loading pins

distance between the centres of the loading pins (3.10) inserted into the holes of the tab plates (3.7)

3.12
impact energy

energy applied to a wedge placed on a notch formed at the edge of a test piece (3.6) to initiate a brittle

crack (3.4)
3.13
crack branching

case when two or more cracks form during initiation or propagation of a brittle crack (3.4)

Note 1 to entry: Secondary cracks that are not a main crack are called branch cracks.

3.14
main crack
crack with the longest propagation length when crack branching (3.13) occurs
3.15
shear lip

fracture surface generated by ductile fracture adjacent to the front and back surfaces of a steel plate

3.16
stretch zone
plastic deformation at tip of the arrested crack front
4 Symbols
For the purposes of this document, the symbols given in Table 1 apply.
Table 1 — Symbols used in this document
Symbol Unit Designation
a mm Arrest crack length
B mm Test piece thickness
B mm Extension plate thickness
a 1/2 = -3/2 -3/2
0,031 6 MPa m 1 N mm =0,031 6 MN m .
2 © ISO 2019 – All rights reserved
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ISO 20064:2019(E)
Table 1 (continued)
Symbol Unit Designation
B mm Tab plate thickness
E MPa Modulus of elasticity
E J Impact energy
E J Strain energy stored in a test piece
E J Total strain energy stored in extension plates and tab plates
F MN Applied force
1/2
MPa m
K Stress intensity factor
3/2 a
(N/mm )
1/2
MPa m
K Arrest toughness
3/2 a
(N/mm )
L mm Test piece length
L mm Distance between loading pins
L mm Extension plate length
L mm Tab plate length
R MPa Yield stress at room temperature
T °C
Arrest temperature
T K
caK
W mm Test piece width
W mm Extension plate width
W mm Tab plate width
x mm Coordinate of the main crack tip in the width direction
x mm Coordinate of the longest branch crack tip in the width direction
y mm Coordinate of the main crack tip in the loading direction
y mm Coordinate of the longest branch crack tip in the loading direction
σ MPa Applied stress in unnotched cross section
a 1/2 = -3/2 -3/2
0,031 6 MPa m 1 N mm =0,031 6 MN m .
5 Test equipment
5.1 General

The following provides specifications for the testing machine needed for conducting the test. The

testing machine is used to apply tensile force to an integrated test piece, and the impact equipment is

used to initiate a brittle crack on the test piece.
5.2 Testing machine
5.2.1 Force implementation

Tensile force to an integrated test piece can be either hydraulically or mechanically applied using either

force or displacement control.
5.2.2 Calibration of the load cell

Load cells shall be calibrated to check the accuracy of force measurement. The force-measuring system

of the testing machine shall be calibrated in accordance with ISO 7500-1, class 1, or better.

© ISO 2019 – All rights reserved 3
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ISO 20064:2019(E)
The accuracy of the load cells shall be 1 % of the full scale or less.
5.2.3 Force measurement
Force is measured using a calibrated load cell attached to the testing machine.
5.2.4 Method for force transfer to integrated test piece

The force applied to an integrated test piece by the test machine shall be via a clevis pin type loading

method as shown in Figure 1. Centres of the loading pins at both ends shall align with the neutral axis

of the integrated test piece.
Key
1 integrated test piece
2 load clevis
3 pin
Force.
Figure 1 — Method for loading an integrated test piece through loading pins
5.2.5 Loading direction

The test machine may be either horizontal or vertical. In the case of the horizontal direction, the test

piece surfaces shall be placed either perpendicular or parallel to the ground. However, when using the

parallel position, care should be taken to ensure that the temperature difference between the top and

bottom surfaces of the test piece is within the values specified in 7.1.1.2.
5.2.6 Distance between the loading pins

The distance between the loading pins, L , as defined in Figure 8, shall be 3,4W or more for preventing

force drop by a reflection of stress wave at the loading pins. Since the distance between the loading

pins potentially has an effect on the force drop associated with crack propagation, especially for a long

[11]

arrested crack, the validity of the test results shall be verified using the method described in 9.1 .

5.3 Impact equipment
5.3.1 Impact methods

Recommended methods for applying an impact force to a wedge mounted on the notch of an integrated

test piece include the drop-weight type and the air gun type, as shown in Figure 2 a) and Figure 2 b),

respectively. The drop weight type method applies an impact force to the wedge by freely dropping a

weight from a predetermined height. The air gun type method applies an impact force to the wedge by

4 © ISO 2019 – All rights reserved
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ISO 20064:2019(E)

introducing a predetermined gas pressure into a piston-sealed cylinder, and then releasing the lock of

the piston.

The wedge shall be of sufficient hardness not to plastically deform during impact. The wedge thickness

shall be equal to or greater than that of the test piece, and the wedge angle shall be greater than that

of the notch formed in the test piece and shall have a shape capable of opening up the notch of the test

piece. The recommended shape of the wedge is shown in Figure 3.
a) Drop weight type b) Air gun type
Key
1 drop weight (before impact)
2 drop weight (after impact)
3 wedge
4 cylinder
5 piston (before impact)
6 piston (after impact)
Free fall of drop weight.
Figure 2 — Impact apparatus
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ISO 20064:2019(E)
Dimensions in millimetres
Key
1 wedge
2 test piece
Figure 3 — Recommended wedge shape
5.3.2 Impact energy calculation

Formula (1) shall be used to calculate the impact energy for the drop weight type method.

Em= gh (1)
where
m is the mass of the drop weight (kg);
g is the acceleration of gravity (9,81 m/s );
h is the height from the wedge to the drop weight (m).

For the air gun type method, an energy conversion table specific to the impact apparatus used for

testing shall be used to calculate the impact energy. Impact energy shall be controlled by changing the

cylinder pressure.

NOTE The energy conversion table is generally provided by the manufacturer of the air gun type impact

apparatus.

Setting of the impact energy value before the test and its validity check after the test are described in

7.2 and 9.2, respectively.
5.3.3 Reaction force receivers

To suppress the bending moment caused by impact, a reaction force receiver shall be applied opposite

the impact edge of the integrated test piece. Two types of recommended reaction force receivers are

shown in Figure 4. The floor type, shown in Figure 4 a), is fixed on the ground. The hold type, shown

[12][13][14]

in Figure 4 b), connects to the frame of the impact apparatus . Other methods which are

equivalent to the methods shown in Figure 4 a) and Figure 4 b) may be applied.
6 © ISO 2019 – All rights reserved
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ISO 20064:2019(E)
a) Floor type b) Hold type
Key
1 impact apparatus
2 wedge
3 test piece
4 reaction force receiver
5 ground
6 frame
Figure 4 — Fixing methods of reaction force receivers
6 Test pieces
6.1 Test piece configurations

The standard test piece configuration is shown in Figure 5. Table 2 shows the ranges of test piece

[11][12][15]
thicknesses, widths and width-to-thickness ratios .

The test piece length shall be equal to or greater than 500 mm or W, whichever is greater.

A crack starter notch shall be introduced at a test piece edge. The notch may be a mechanical or pressed

notch. The pressed notch can be formed by placing a jig having a sharp edge on the bottom of the

mechanical notch and applying hydraulic pressure to the jig. The length of the notch shall be 29 mm.

No other requirements are specified for the notch shape, but the notch edge shape shall be designed so

that a brittle crack is initiated by impact within the impact energy value specified in 9.2 but does not

initiate during force increase before attaining a specified force value. Figure 6 shows the recommended

notch configurations. Side-grooves at the notch-root may be machined on both faces of the test piece to

minimize crack deviation and branching. However, the side-groove depth shall be equal to or less than

0,1B and the side-groove length measured from the notch-root shall be equal to or less than B or 0,1W,

whichever is smaller. A notch of the same length shall be introduced at the opposite edge to avoid bending

moment by matching the net-section centre with the loading axis. In case the side-grooves are applied,

however, the notch length at the opposite edge shall be determined so that there is no bending moment.

© ISO 2019 – All rights reserved 7
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ISO 20064:2019(E)
Table 2 — Dimensions of test pieces
Thickness Width Width to thickness ratio
350 mm ≤ W ≤ 1 000 mm
6 mm ≤ B ≤ 200 mm W/B ≥ 5
(standard width: W = 500 mm)
Dimensions in millimetres
Key
W 500
L 500
Figure 5 — Standard test piece configuration
Dimensions in millimetres
a) Mechanical notch b) Pressed notch
Key
1 pressed notch
Figure 6 — Recommended notch configurations of test pieces
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ISO 20064:2019(E)
6.2 Configurations of extension plates and tab plates
6.2.1 General

The definitions of the dimensions of the extension plates and tab plates are shown in Figure 7. Typical

examples are shown in Figure 8.

As for loading pins, either the single-pin type or the double-pin type shall be used.

a) Single-pin type
b) Double-pin type
Key
1 tab plate (thickness: B )
2 extension plate (thickness: B )
3 test piece (thickness: B)
Figure 7 — Definitions of dimensions of extension plates and tab plates
© ISO 2019 – All rights reserved 9
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ISO 20064:2019(E)
a) Example 1
b) Example 2
c) Example 3
10 © ISO 2019 – All rights reserved
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ISO 20064:2019(E)
d) Example 4
Figure 8 — Examples of configurations of extension plates and tab plates
6.2.2 Extension plates
[10][11][15]

The tolerances of extension plate dimensions are shown in Table 3 . When the lengths of the

extension plates attached to the two ends of a test piece are different, the shorter length shall be used

as the extension length, L .
Table 3 — Tolerances of extension plate dimensions
Thickness 0,8t ≤ B ≤ 1,5t
Width W ≤ W ≤ 2,0W
Total length of a test piece and extension plates L + 2L ≥ 3,0W

(Total length of a test piece and a single extension plate L + L ) (L + L ≥ 2,0W)

ex ex
Length to width ratio L /W ≥ 1,0
6.2.3 Tab plates
The tab plate width, W , shall be equal to o
...

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