ISO 26843:2015

INTERNATIONAL ISO
STANDARD 26843
First edition
2015-12-15
Metallic materials — Measurement
of fracture toughness at impact
loading rates using precracked
Charpy-type test pieces
Matériaux métalliques — Mesure de la ténacité d’éprouvettes type
Charpy préfissurées soumises à un chargement d’impact
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
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ii © ISO 2015 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Symbols . 1
4 Principle . 3
5 Test specimens. 5
6 Testing machines . 6
7 Test procedures and measurements. 6
7.1 General . 6
7.2 Impact velocity . 7
7.3 Time to fracture . 7
7.4 Multiple specimen tests. 7
7.5 Single-specimen tests . 7
7.6 Post-test crack length measurements . 8
8 Evaluation of fracture mechanics parameters . 8
9 Test report . 9
9.1 Organization . 9
9.2 Specimen, material, and test environment . 9
9.2.1 Specimen description . 9
9.2.2 Specimen dimensions . 9
9.2.3 Material description . . 9
9.2.4 Test environment .10
9.3 Fatigue precracking conditions .10
9.4 Test data qualification .10
9.4.1 Limitations .10
9.4.2 Crack length measurements .10
9.4.3 Fracture surface appearance .10
9.4.4 Resistance curves .10
9.4.5 Checklist for data qualification .10
9.5 Test results.11
Annex A (normative) Test machines suitable for each test procedure .12
Annex B (informative) Estimation of strain rate .13
Annex C (normative) Dynamic evaluation of fracture toughness .14
Annex D (normative) Determination of resistance curves at impact loading rates by
multiple specimen methods .19
Annex E (normative) Estimation of J-Δa R-curves using the normalization method .21
d
Annex F (normative) Determination of characteristic fracture toughness value J .24
0,2Bd
Annex G (normative) Validity criteria .25
Annex H (normative) Determination of fracture toughness in terms of J-integral .27
Annex I (informative) Example test reports .29
Bibliography .34
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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The committee responsible for this document is ISO/TC 164, Mechanical testing of metals, Subcommittee
SC 4, Toughness testing — Fracture (F), Pendulum (P), Tear (T).
iv © ISO 2015 – All rights reserved

Introduction
This International Standard is closely related to ISO 14556 and was derived from a draft procedure
prepared by the Working Party “European Standards on Instrumented Precracked Charpy Testing”
of the European Structural Integrity Society (ESIS) Technical Subcommittee on Dynamic Testing at
Intermediate Strain Rates (TC5).
INTERNATIONAL STANDARD ISO 26843:2015(E)
Metallic materials — Measurement of fracture toughness
at impact loading rates using precracked Charpy-type test
pieces
1 Scope
This International Standard specifies requirements for performing and evaluating instrumented
precracked Charpy impact tests on metallic materials using a fracture mechanics approach. Minimum
requirements are given for measurement and recording equipment such that similar sensitivity and
comparable measurements are achieved.
Dynamic fracture mechanics properties determined using this International Standard are comparable
with conventional large-scale fracture mechanics results when the corresponding validity criteria are
met. Because of the small absolute size of the Charpy specimen, this is often not the case. Nevertheless,
the values obtained can be used in research and development of materials, in quality control, and to
establish the variation of properties with test temperature under impact loading rates.
Fracture toughness properties determined through the use of this International Standard may differ
from values measured at quasistatic loading rates. Indeed, an increase in loading rate causes a decrease
in fracture toughness when tests are performed in the brittle or ductile-to-brittle regimes; the opposite
is observed (i.e. increase in fracture toughness) in the fully ductile regime. More information on the
dependence of fracture toughness on loading (or strain) rate is given in Reference [1]. In addition, it is
generally acknowledged that fracture toughness also depends on test temperature. For these reasons,
the user is required to report the actual test temperature and loading rate for each test performed.
In case of cleavage fracture of ferritic steels in the ductile-to-brittle transition region, variability can
be very large and cannot be adequately described by simple statistics. In this case, additional tests are
required and the analysis is to be performed using a statistical procedure applicable to this type of test,
see for example Reference [2].
NOTE Modifications to the analytical procedures prescribed in Reference [2] might be necessary to account
for the effect of elevated (impact) loading rates.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 148-1, Metallic materials — Charpy pendulum impact test — Part 1: Test method
ISO 148-2, Metallic materials — Charpy pendulum impact test — Part 2: Verification of testing machines
ISO 12135, Metallic materials — Unified method of test for the determination of quasistatic fracture toughness
ISO 14556, Steel — Charpy V-notch pendulum impact test — Instrumented test method
ISO 26203-2, Metallic materials — Tensile testing at high strain rates — Part 2: Servo-hydraulic and
other test systems
3 Symbols
For the purposes of this International Standard, the following symbols given in Table 1 apply.
Table 1 — Symbols and definit
...