ISO 12135:2021

INTERNATIONAL ISO
STANDARD 12135
Third edition
2021-07
Metallic materials — Unified method
of test for the determination of
quasistatic fracture toughness
Matériaux métalliques — Méthode unifiée d'essai pour la
détermination de la ténacité quasi statique
Reference number
©
ISO 2021
© ISO 2021
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ii © ISO 2021 – All rights reserved

Contents Page
Foreword .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 General requirements . 5
5.1 General . 5
5.2 Fracture parameters. 7
5.3 Fracture toughness symbols . 8
5.4 Test specimens . 8
5.4.1 Specimen configuration and size . 8
5.4.2 Specimen preparation .13
5.5 Pre-test requirements .19
5.5.1 Pre-test measurements .19
5.5.2 Crack shape/length requirements .19
5.6 Test apparatus .19
5.6.1 Calibration .19
5.6.2 Force application .20
5.6.3 Displacement measurement .20
5.6.4 Test fixtures .20
5.7 Test requirements .24
5.7.1 Three-point bend testing .24
5.7.2 Compact tension testing .24
5.7.3 Specimen test temperature.24
5.7.4 Recording .25
5.7.5 Testing rates .25
5.7.6 Test analyses .25
5.8 Post-test crack measurements .25
5.8.1 General.25
5.8.2 Initial crack length, a .25
5.8.3 Stable crack extension, Δa .30
5.8.4 Unstable crack extension .30
6 Determination of fracture toughness for stable and unstable crack extension .31
6.1 General .31
6.2 Determination of plane strain fracture toughness, K .32
lc
6.2.1 General.32
6.2.2 Interpretation of the test record for F .32
Q
6.2.3 Calculation of K .33
Q
6.2.4 Qualification of K as K .34
Q lc
6.3 Determination of fracture toughness in terms of δ .34
6.3.1 Determination of F and V , F and V , or F and V .34
c c u u uc uc
6.3.2 Determination of F and V .35
m m
6.3.3 Determination of V .36
p
6.3.4 Calculation of δ .36
6.3.5 Qualification of δ fracture toughness value .37
6.4 Determination of fracture toughness in terms of J .38
6.4.1 Determination of F and V or q , F and V or q , or F and V or q .38
c c c u u u uc uc uc
6.4.2 Determination of F and q .38
m m
6.4.3 Determination of U .38
p
6.4.4 Calculation of J .39
6.4.5 Qualification of J fracture toughness value .40
7 Determination of resistance curves δ-Δa and J-Δa and initiation toughness δ and
0,2BL
J and δ and J for stable crack extension .41
0,2BL i i
7.1 General .41
7.2 Test procedure .41
7.2.1 General.41
7.2.2 Multiple-specimen procedure .41
7.2.3 Single-specimen procedure .41
7.2.4 Final crack front straightness .42
7.3 Calculation of J and δ .42
7.3.1 Calculation of J .42
7.3.2 Calculation of δ .42
7.4 R-curve plot .43
7.4.1 Plot construction .44
7.4.2 Data spacing and curve fitting .45
7.5 Qualification of resistance curves .46
7.5.1 Qualification of J-Δa resistance curves .46
7.5.2 Qualification of δ−Δa resistance curves .46
7.6 Determination and qualification of J and δ .47
0,2BL 0,2BL
7.6.1 Determination of J .47
0,2BL
7.6.2 Determination of δ .48
0,2BL
7.7 Determination of initiation toughness J and δ by scanning electron microscopy (SEM) .49
i i
8 Test report .49
8.1 Organization .49
8.2 Specimen, material and test environment .50
8.2.1 Specimen description .50
8.2.2 Specimen dimensions .50
8.2.3 Material description .
...