Evaluation of the single edge notch tension specimen for quantifying fracture toughness Participation in a round-robin test program
Christopher Bayley DRDC – Atlantic Research Centre
Defence Research and Development Canada
Scientific Report
DRDC-RDDC-2015-R156
August 2015
© Her Majesty the Queen in Right of Canada, as represented by the Minister of National Defence, 2015
© Sa Majesté la Reine (en droit du Canada), telle que représentée par le ministre de la Défense nationale,
2015
DRDC-RDDC-2015-R156 i
Abstract
DRDC was asked to participate in a round-robin program investigating a new test protocol to
measure the fracture toughness of steels and welds. The round-robin program utilized a testing
procedure being examined by the Pipeline Research Council International using a single edge
notch tension (SENT) specimen, rather than the more conventional single edge bend specimen.
Twelve SENT specimens were tested in a 500 kN test frame at room temperature with notches
located in either the base metal, fusion line or weld centerline. Periodic unloading compliance
measurements were programmed into a customized control routine in order to estimate the crack
length throughout the test duration. At each unloading point, the crack tip opening displacement
(CTOD) was determined by either a geometrically based Double Clip Gauge (DCG) procedure,
or computed from the elastic plastic fracture toughness parameter J. Tearing resistance curves
were computed, with significant discrepancies noted between the two different fracture toughness
measurement approaches. The most striking difference was associated with the fusion line
specimens, and was attributed to invalid material constants. Since the DCG approach does not
require an assumption of the mechanical properties of the given material, it is likely a better
approach for heterogeneous materials or when the notch is located within a graded
microstructure.
Significance to defence and security
The fracture toughness of materials is dependent on the specimen dimensions, and loading
configuration, as well as material properties. Conventionally fracture toughness specimens are
subjected to a bending load however this configuration is known to yield overly-conservative
results, particularly when the results are applied to structures which are loaded predominantly in
tension. By testing the sample in the same loading configuration as the structure, more realistic
conclusions can be expected.
From a Naval perspective, the use of fracture toughness values obtained from SENT specimen
could provide a more accurate means of the describing the resistance of a hull structural material
to the initiation of a ductile crack. In particular, it may be more appropriate for structures which
are subjected to primarily tensile loading during either hogging or sagging events. Fracture
toughness values obtained from SENT specimens may provide a more realistic analysis of
residual strength and provide more accurate data for determining critical crack lengths in
structural analyses.
ii DRDC-RDDC-2015-R156
Résumé
On a demandé à RDDC de participer à un programme visant l’étude, à tour de rôle, d’un nouveau
protocole d’essai élaboré pour mesurer la ténacité à la rupture d’aciers et de soudures. Le
programme reposait sur une procédure d’essai étudiée par Pipeline Research Council
International au moyen d’une éprouvette de traction entaillée d’un côté (ETEUC), plutôt que
d’une éprouvette de flexion plus classique entaillée d’un côté.
Douze ETEUC ont été éprouvées dans un bâti d’essai de 500 kN, à la température ambiante,
après avoir été entaillées dans le métal de base, dans la ligne de fusion ou dans l’axe de soudure.
Des mesures périodiques de conformité et de décharge ont été programmées dans une routine de
contrôle personnalisée pour estimer la longueur de fissuration tout au long de l’essai. Le
déplacement de l’extrémité de fissure a été déterminé à chaque point de décharge en suivant une
procédure géométrique impliquant l’utilisation d’une jauge à pince double ou en le calculant
d’après le paramètre J de ténacité à la rupture plastique et élastique. Après le calcul de courbes de
ténacité, d’importantes anomalies on été relevées entre les deux approches distinctes de mesure
de la ténacité, la plus marquée étant associée aux éprouvettes de ligne de fusion et attribuée à des
constantes de matière invalides. L’approche impliquant l’utilisation d’une jauge à pince double se
prête probablement mieux aux matières hétérogènes ou aux entailles situées dans une
microstructure stratifiée, car elle n’exige aucune présomption des propriétés mécaniques d’une
matière donnée.
Importance pour la défense et la sécurité
La ténacité à la rupture des matières dépend de leurs propriétés, de la taille des éprouvettes et de
la configuration de charge. Bien que les éprouvettes de ténacité soient habituellement soumises à
une charge de flexion, cette configuration a donné des résultats trop prudents, surtout lorsque les
résultats étaient appliqués à des structures principalement soumises à une charge de traction. En
mettant à l’essai les éprouvettes selon la même configuration de charge que la structure, on
pourrait s’attendre à tirer des conclusions plus réalistes.
Du point de vue naval, l’utilisation de valeurs de ténacité à la rupture issues d’une ETEUC devrait
permettre de décrire plus exactement la ténacité d’une matière de coque à la rupture ductile. Elle
pourrait, plus particulièrement, s’avérer davantage appropriée dans le cas de structures (coques)
principalement soumises à des charges de tension provoquant un fléchissement vers le haut ou
vers le bas. Les valeurs de ténacité à la rupture issues d’une ETEUC pourraient permettre une
analyse plus réaliste de la résistance résiduelle et fournir des données d’analyse structurale plus
exactes aux fins de la détermination des longueurs de fissures critiques.
DRDC-RDDC-2015-R156 iii
Table of contents
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Significance to defence and security . . . . . . . . . . . . . . . . . . . . . . i
Résumé . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
Importance pour la défense et la sécurité . . . . . . . . . . . . . . . . . . . . ii
Table of contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
List of figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
List of tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Testing Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1 Test Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3 Crack Opening Displacement (COD) Gauges . . . . . . . . . . . . . . 5
2.4 Knife Blocks and Fixtures . . . . . . . . . . . . . . . . . . . . . 6
2.5 Specimen Preparation . . . . . . . . . . . . . . . . . . . . . . . 8
2.6 Test Procedure . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.6.1 Displacement Control Ramping . . . . . . . . . . . . . . . . 10
2.6.2 Compliance Cycling . . . . . . . . . . . . . . . . . . . . . 10
2.6.3 Termination . . . . . . . . . . . . . . . . . . . . . . . . 10
2.6.4 Revealing the Fracture Surfaces . . . . . . . . . . . . . . . . 10
2.6.5 Data Acquisition . . . . . . . . . . . . . . . . . . . . . . 10
3 Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1 Strain Hardening Exponent . . . . . . . . . . . . . . . . . . . . . 12
3.2 Specimen dimensions . . . . . . . . . . . . . . . . . . . . . . . 13
3.3 Physical Crack Length Measurements . . . . . . . . . . . . . . . . . 15
3.4 Compliance based crack length estimates . . . . . . . . . . . . . . . . 15
3.5 Fusion line notched specimens – Metallographic Sample Preparation . . . . . 18
3.6 Determination of CTOD . . . . . . . . . . . . . . . . . . . . . . 18
3.6.1 Calculation from the double clip gauge . . . . . . . . . . . . . . 18
3.6.2 Calculation of CTOD from J . . . . . . . . . . . . . . . . . . 19
4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
6 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . 27
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Annex A Certificates . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Annex B MTS 609 alignment apparatus and 709 alignment software . . . . . . . . . 35
iv DRDC-RDDC-2015-R156
Appendix 1 Base Metal . . . . . . . . . . . . . . . . . . . . . . . . . 37
Appendix 2 All Weld Metal . . . . . . . . . . . . . . . . . . . . . . . . 43
Appendix 3 Notch Center Fusion Line . . . . . . . . . . . . . . . . . . . . 50
List of symbols/abbreviations/acronyms/initialisms . . . . . . . . . . . . . . . . 59
DRDC-RDDC-2015-R156 v
List of figures
Figure 1: Load versus crack mouth opening displacement trace. . . . . . . . . . . 3
Figure 2: Load Train showing the various components on either side of the specimen. . 4
Figure 3: Two narrow body COD gauges mounted on sample. . . . . . . . . . . . 5
Figure 4: As-received COD notch details. . . . . . . . . . . . . . . . . . . . 6
Figure 5: Custom designed knife blocks. . . . . . . . . . . . . . . . . . . . . 7
Figure 6: As specified 60o knife edges. The near planar contact resulted in the relative
motion of the contact point with the rotation of the knife edges around the
COD arm, as evidenced by fretting on the surfaces of the knife edges. . . . . 8
Figure 7: Sharpened knife edge design, decreased the relative motion of the contact
point during the rotation. Note that the termination of the knife edges were left
at 60o. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 8: Machine drawing for the specification of the side grooves. . . . . . . . . 9
Figure 9: Fitting of the strain hardening exponent to the provided stress-strain data. . . 13
Figure 10: Annotated illustration of the specimen showing the dimensions. . . . . . . 14
Figure 11: Fracture surface of W2-A1showing the points marking the notch (green) and
extent of ductile crack extensions (red). . . . . . . . . . . . . . . . . 15
Figure 12: Elastic unloading-reloading compliance cycles showing a characteristic kink
(Sample W2-A2). . . . . . . . . . . . . . . . . . . . . . . . . . 16
Figure 13: Mean and ±95% confidence intervals determined from the compliance based
crack length estimates. Peak load at compliance associated with cycle 22
(Sample W2-A2). . . . . . . . . . . . . . . . . . . . . . . . . . 17
Figure 14: Fitting of -a values to determine a0q (Sample W2-A2). . . . . . . . . . . 18
Figure 15: Illustration of triangulation scheme used to determine the CTOD (DCG) from
the two crack opening displacement gauges and the offset knife edges. . . . 19
Figure 16: Comparison of the CTODJ-R curves. The three other BM samples were
omitted due to inconsistencies associated with their crack length
measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Figure 17: CTODDCG- R curves. . . . . . . . . . . . . . . . . . . . . . . . . 23
Figure 18: J-R curve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Figure A.1: Clip Gauge Calibration Certificate. . . . . . . . . . . . . . . . . . . 31
Figure A.2: Clip Gauge Calibration Certificate. . . . . . . . . . . . . . . . . . . 32
Figure A.3: Frame 2 Load Cell Calibration Certificate. . . . . . . . . . . . . . . . 33
Figure A.4: Frame 2 LVDT Calibration Certificate. . . . . . . . . . . . . . . . . 34
Figure B.1: Alignment Output. . . . . . . . . . . . . . . . . . . . . . . . . 36
vi DRDC-RDDC-2015-R156
Figure A1.1: Base Metal A1. . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Figure A1.2: Base Metal E1. . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Figure A1.3: Base Metal H1. . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Figure A1.4: Base Metal H1 – Crack Length. . . . . . . . . . . . . . . . . . . . 40
Figure A1.5: Base Metal K1. . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Figure A1.6: Base Metal K1 – Crack Lengths. . . . . . . . . . . . . . . . . . . . 42
Figure A2.1: All Weld Metal W2-A1. . . . . . . . . . . . . . . . . . . . . . . 43
Figure A2.2: All Weld Metal W2-A1 – Crack Lengths. . . . . . . . . . . . . . . . 44
Figure A2.3: All Weld Metal W2-A3. . . . . . . . . . . . . . . . . . . . . . . 45
Figure A2.4: All Weld Metal W2-A3 – Crack Lengths. . . . . . . . . . . . . . . . 46
Figure A2.5: All Weld Metal W2-A5. . . . . . . . . . . . . . . . . . . . . . . 47
Figure A2.6: All Weld Metal W2-A5 – Crack Lengths. . . . . . . . . . . . . . . . 48
Figure A2.7: All Weld Metal W2-A8. . . . . . . . . . . . . . . . . . . . . . . 49
Figure A3.1: Notch Fusion Line W2-A2. . . . . . . . . . . . . . . . . . . . . . 50
Figure A3.2: Notch Fusion Line W2-A2 – Crack Lengths. . . . . . . . . . . . . . . 51
Figure A3.3: Notch Fusion Line W2-A4. . . . . . . . . . . . . . . . . . . . . . 52
Figure A3.4: Notch Fusion Line W2-A4 – Crack Lengths. . . . . . . . . . . . . . . 53
Figure A3.5: Notch Fusion Line W2-A6. . . . . . . . . . . . . . . . . . . . . . 54
Figure A3.6: Notch Fusion Line W2-A6 – Crack Lengths. . . . . . . . . . . . . . . 55
Figure A3.7: Notch Fusion Line W2-A7. . . . . . . . . . . . . . . . . . . . . . 56
Figure A3.8: Notch Fusion Line W2-A7 – Crack Lengths. . . . . . . . . . . . . . . 57
DRDC-RDDC-2015-R156 vii
List of tables
Table 1: ASCII data file column labels. . . . . . . . . . . . . . . . . . . . . 11
Table 2: Segment values and corresponding meaning. . . . . . . . . . . . . . . 11
Table 3: Summary of material parameters. . . . . . . . . . . . . . . . . . . . 13
Table 4: Physical specimen measurements (AWM = All Weld Metal, NCF = Notch
Centerline Fusion). . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 5: Test Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 6: Crack length measurements. Highlighted cell correspond to the specimens
which used a 60o knife edge. af is the calculated crack extension, while afp is
the optically measured crack extension. . . . . . . . . . . . . . . . . 22
Table 7: Power Law Fitting Parameters. . . . . . . . . . . . . . . . . . . . 25
viii DRDC-RDDC-2015-R156
Acknowledgements
The technical support of Mr. Joel Higgins of the DRDC – Atlantic Research Center is
acknowledged, particularly his unwavering attention to detail. The assistance provided by Nick
Pussegoda and Morvarid Ghovanlou of BMT Fleet Technology in facilitating the round-robin is
acknowledged.
DRDC-RDDC-2015-R156 1
1 Introduction
The accurate prediction of a material’s fracture toughness plays a critical role in any structural
integrity assessment associated with either the validation of a new design, or critical defect
analyses. Such structural integrity assessments are based on the presumption that the material
fracture resistance of the component of interest is equivalent to the resistance acquired from the
toughness specimen [1, 2]. Unfortunately this is not always the case, and has led to overly
conservative designs and misleading conclusions in failure analyses. In addition, such overly
conservative conclusions also lead to excessively onerous material selection requirements [2].
This over-conservatism is generally related to differences in crack growth resistance (toughness)
associated with the loss of constraint ahead of the crack tip. Constraint is the product of plastic
strain and stress triaxiality, and is influenced by crack geometry, sample and loading
configuration.
Two approaches have been generally proposed to account for the difference in crack tip
constraints, one approach corrects numerically for the difference in constraint between the test
and actual configuration [1], while the other approach utilizes a specimen configuration which is
more representative of the intended application. It is this second approach which motivates the
development of this single edge notch tension (SENT) testing procedure. The development of the
SENT specimens have been widely received within the pipeline industry as this specimen is
believed to best represent a shallow surface breaking crack subjected to a tensile load [3, 4].
In this body of work, two methods are employed to determine the elastic-plastic fracture
toughness. One of the methods follows the standardized J-integral while the second approach
utilizes a double-clip gauge (DCG) to geometrically relate the mouth opening displacement to the
crack tip opening displacement [5]. The DCG was first proposed in the 1980’s as an alternative to
the more rigorous J-integral based experimental approaches and continued interest in this
technique exists today [6, 7]. The advantage of the DCG method is that it is based on the physical
deformation of the crack tip and does not involve the determination of J, but is based on a simple
geometric relationship. Moore and Pisarski [7] compared the CTOD value obtained from the
DCG and determined them to be within 10% of replica based measurements, at least for shallow
cracks. Yan et al [6] however investigated further the accuracy of the DCG method and
concluded that the accuracy is dependent on the extent of crack tip blunting.
The round-robin was sponsored by the Pipeline Research Council International (PRCI) initiative
and facilitated by BMT Fleet Technology Ltd of Kanata ON. The round-robin results will be
made available to the participants with their results compared to other labs. The final report
accepted by PRCI will be available to the labs; however, it will not be released as a public
document. The intention of PRCI is to have this protocol included as a test standard to develop a
test standard to measure CTOD and J R-curves suitable for use in strain-based engineering
critical assessment analysis of pipelines to predict the tensile strain capacity.
Based on the original invitation to solicit participants, eight were drawn from international
industrial and government research laboratories, six represented utilities, pipeline and steel
producers, five were from asset integrity engineering firms, and two from Academia. The only
other Defense related invitee was from the US Naval Academy. DRDC was pleased to participate
in this round-robin as it provided:
2 DRDC-RDDC-2015-R156
an opportunity for personnel development;
an opportunity to maintain abreast of current trends in fracture toughness testing;
an opportunity to validate testing and analysis procedures; and
an opportunity to establish industrial and governmental collaborative relationships.
DRDC’s motivation for participating is based on the presumed similarities in crack loading
configuration of a through-thickness crack within a nominally tensile stress field. The SENT
specimen may be more representative of the local loading conditions of a crack within the global
hogging and sagging induced moments of a ship structure. The difference in the material
toughness measured by the SENT specimen will assist in determining the inherent conservatism
associated with measurement and application of fracture toughness values acquired from
standardized single edge bend configurations.
The purpose of this report is to evaluate the testing technique on base and weld metals, not to
evaluate the candidate materials selected by the round-robin committee.
DRDC-RDDC-2015-R156 3
2 Testing Procedure
The testing procedure followed the instructions detailed in the test protocol [8], and involved both
a physical testing component in which each specimen was tested and data collected, and post
processing component in which the fracture toughness values were calculated. The physical
testing component involved loading the notched specimens past the maximum load, but before
failure, while recording the signals of load and two crack opening displacement gauges. The
change in crack length was monitored by using the compliance technique and involved periodic
elastic unloading-reloading events. These period unloading-reloading events can be easily
identified in the load displacement trace shown in Figure 1. Following the physical testing
component, the fracture toughness was post-processed using a Matlab script which read in the
data files and computed the components of the elastic-plastic fracture toughness parameter, the
J-Integral. The test procedure measures the materials resistance to stable crack extension, i.e., a
J-R curve. The testing procedure parallels the standardized ASTM E1820 [9] with some notable
differences, namely the specimen dimensions and loading path. In addition the analysis differs in
that there is no attempt to compute an initiation toughness value from the resistance curve.
Unfortunately the preservation of intellectual property rights, the testing protocol cannot be
included. Instead, references to openly available publications are cited where equivalent
formulations can be found.
Figure 1: Load versus crack mouth opening displacement trace.
2.1 Test Setup
All of the testing took place in a 500 kN servo-hydraulic computer controlled test frame. The
specimens were gripped in 250 kN hydraulic grips set at 15 MPa of pressure. Figure 2 illustrates
the load line in between the upper stationary crosshead and the lower hydraulic actuator.
Certificates for the load cell, actuator, and double clip gauges are provided in Annex A.
4 DRDC-RDDC-2015-R156
Figure 2: Load Train showing the various components on either side of the specimen.
2.2 Alignment
Prior to, and after the testing of the third specimen, the alignment of the test frame was checked
and adjusted so that the maximum out-of-plane bending was less than 50 . Alignment checking
followed the MTS 609/709 procedure (see Annex B) yielding a Class 5 alignment as defined by
VAMAS [10].
Stationary Cross Head
Alignment
Fixture
Load Cell
Hydraulic Grip
SENT Specimen
Hydraulic Grip
Actuator Rod
DRDC-RDDC-2015-R156 5
2.3 Crack Opening Displacement (COD) Gauges
Two narrow body crack opening displacement gauges were ordered from Epsilon Technology
(Jackson, WY). The specifications for these custom gauges were based on a standard cantilever
design but with the following additional specifications:
3 mm compressed gauge length;
+7/-1 mm measuring range; and
-40°C to 100°C temperature range.
The width of the gauges was sufficiently narrow as to permit the gauges to sit side-by-side on the
knife edges without touching each other. Figure 3 illustrates the attachment of the gauges within a
pair of external knife edges, while Figure 4 is an annotated image of the machined recess at the
end of the knife edges. The angles of the machined recess are measured as 135o and 48
o and thus
the notch is nearly symmetric (with internal angles of 45-45-90 degrees). In comparison, ASTM
E1820 [9], specifies that the notch geometry on the COD gauges be asymmetric with internal
angles of 70-20-90 degrees. In the case of ASTM E1820, the COD notches are paired with 60o
knife edges, the same knife edge angle that is specified in the test protocol. As discussed later,
these differences in internal angles are believed to have resulted in some measurement error.
Figure 3: Two narrow body COD gauges mounted on sample.
6 DRDC-RDDC-2015-R156
Figure 4: As-received COD notch details.
2.4 Knife Blocks and Fixtures
Custom knife blocks shown in Figure 5 were developed and manufactured in order to
accommodate the offset double clip gauges. While a knife edge angle of 60o was originally
specified in the test protocol (paragraph 7.3.6), it was changed in order to accommodate the
recess in the arms of the COD gauge. Contact between the 60o knife edge and the COD arm
recess was nearly planar (Figure 6), rather than linear (Figure 7). The planar surfaces resulted in
the contact point changing during rotation, as evidenced by both a hysteresis in the
loading-unloading compliance, and visible fretting on the internal surfaces of the knife edges. The
modified design decreased the knife edge angle to 20o, thus improving the contact between the
knife edge and COD notch recess.
47.92o
135.22o
DRDC-RDDC-2015-R156 7
Figure 5: Custom designed knife blocks.
8 DRDC-RDDC-2015-R156
Figure 6: As specified 60o knife edges. The near planar contact resulted in the relative motion
of the contact point with the rotation of the knife edges around the COD arm,
as evidenced by fretting on the surfaces of the knife edges.
Figure 7: Sharpened knife edge design, decreased the relative motion of the contact point
during the rotation. Note that the termination of the knife edges were left at 60o.
2.5 Specimen Preparation
A total of 12 specimens, four base metal, four fusion and four notch centered fusion were
delivered by the round-robin organizers. The material selected was a welded American Petroleum
Institute API low alloy steel grade 550 (X80) pipe, while the welding process and filler metal
were not disclosed by the round-robin facilitators.
DRDC-RDDC-2015-R156 9
The specimens came pre-machined with electric discharge machined (EDM) notches located in
the areas of interest. As directed by the test protocol, side-grooves were machined on the notch
plane in order to increase the crack-tip constraint. The specifications for the side grooves and
knife block attachments are shown in Figure 8. The side grooves were machined using an EDM
process with a 0.010” wire. While the location of the knife block attachment holes was specified
in the test protocol (para 7.3.3) as being 1.5-2 times the screw diameter (i.e., 3–4 mm), the knife
block design and thickness of the COD arms precluded locating the screw holes so close to the
notch. Instead, they were specified as 5.35 mm from the notch centerline. Apart from the location
of the knife block screw holes, other details including the screw hole depth and spacing was in
accordance with the test protocol Paragraph 7.3.3.
The test protocol does not involve fatigue pre-cracking the specimens. Rather the crack growth
develops from the ends of the EDM machined notch.
Figure 8: Machine drawing for the specification of the side grooves.
2.6 Test Procedure
Following a series of loading-unloading cycles to ensure that the COD gauges were seated within
the knife blocks, the testing procedure commenced. Testing involved loading under displacement
10 DRDC-RDDC-2015-R156
control until a pre-determined load drop was recorded. The testing procedure was programmed
into an MTS Multi-Purpose Elite test method. As the test method evolved over the course of the
testing process, slight procedural differences existed between specimens.
2.6.1 Displacement Control Ramping
Under actuator displacement control, increments of 0.035–0.065 mm were specified between the
compliance cycles. A constant displacement rate was used to ensure that the time required to
reach 0.5 Py was within the specified 0.3–3 min (18–180 s) (paragraph 8.7.2).
2.6.2 Compliance Cycling
The compliance crack length measurement technique was employed in order to estimate the
current crack length, and involved five sets of un-loading reloading cycles applied under load
control. The minimum compliance load was selected as the greater of 100N or 40% of the
maximum load prior to unloading, while the maximum compliance load was specified as either
100% or 95% of the load just prior to the unloading sequence. In all cases the load range of the
compliance cycles was within the specified 0.35 to 0.5 PY (paragraph 8.7.5). Specimen to
specimen procedural differences arose, as the compliance cycle minima and maxima loads were
fine-tuned to ensure that the unloading-loading cycle was elastic. Compliance cycles were tested
under load control with a sinusoidal shape and a loading rate of ±10 kN/s. Following the last
loading segment, a 1-second hold under force control was specified.
2.6.3 Termination
Termination of the program was set to either a 15% or 20% reduction in load. The decision to
reduce to load reduction to 15% was in response to two specimens failing prior to attaining the
required 20% load drop (paragraph 8.7.6). However, later it was determined that their failures
were related to a control issue, and after mitigation measures were introduced, the specified 20%
load drop was re-introduced. At the specified load-drop, the control mode was switched to
load-control and ramped to 0 kN at a rate of -5 kN/s.
2.6.4 Revealing the Fracture Surfaces
For the specimens which did not fracture, they were heat tinted in order to permanently mark the
extent of ductile crack tearing. Heat tinting was performed by placing the specimens in a
pre-heated 300C furnace and holding for 30 minutes (paragraph 8.8.1). After cooling to ambient
temperature, the specimen was quenched in a bath of liquid nitrogen. Once cooled, half of the
specimen was clamped in a vise, and the overhanging part was struck with a hammer, fracturing
the specimen in half.
2.6.5 Data Acquisition
The two CODs, actuator displacement, force, and time signals were acquired at a rate of 30 Hz
throughout the duration of the test, and exported as an ASCII comma-separated variable (CSV)
file. Data was saved in engineering units as per the column labels specified in Table 1.
DRDC-RDDC-2015-R156 11
Table 1: ASCII data file column labels.
Col 1 Col 2 Col 3 Col. 4 Col 4 Col 5
COD2 COD1 Segment Count Axial Displ Force Running Time
(mm) (mm) (Unitless) (mm) (kN) (s)
The Segment count of column 3 is an index which identifies the various segments of the control
program, and was exported in the data acquisition file in order to identify the compliance cycles
from the ramping and holding portions of the datafile. The segment values and their
corresponding meaning are listed in Table 2.
Table 2: Segment values and corresponding meaning.
Segment Value Meaning
0 Actuator Ramp
0.5 5 s Force control hold
1.0 Compliance Unloading Segment – Cycle 1
1.5 Compliance Loading Segment – Cycle 1
2.0 Compliance Unloading Segment – Cycle 2
2.5 Compliance Loading Segment – Cycle 2
3.0 Compliance Unloading Segment – Cycle 3
3.5 Compliance Loading Segment – Cycle 3
4.0 Compliance Unloading Segment – Cycle 4
4.5 Compliance Loading Segment – Cycle 4
5.0 Compliance Unloading Segment – Cycle 5
5.5 Compliance Loading Segment – Cycle 5
6.0 Ramp to 100% of Load
6.5 1 s Force control hold
12 DRDC-RDDC-2015-R156
3 Data Analysis
The analysis routine modified an existing ASTM E1820 Matlab function file. The code was
modified in order to accommodate the calculation of the CTOD from the double clip gauges,
along with the necessary changes to the compliance based expression. All verification checks
provided in the test protocol were confirmed, ensuring that the equations had been correctly
transcribed within the analysis module.
3.1 Strain Hardening Exponent
The strain hardening exponent (n) was obtained from the following power-law hardening
expression to stress-strain data for the base and weld metals.
휀 =𝜎𝑌𝑆
𝐸�
𝜎
𝜎𝑌𝑆
1𝑛
In these expressions and are the true strain and true stress, YS is the yield stress and E the
modulus of elasticity. The strain hardening exponent (n) was obtained by first taking natural
logarithms of each side, followed by using a least squares estimation process.
ln �휀 ∙ 𝐸
𝜎𝑌𝑆 =
1
𝑛∙ ln �
𝜎
𝜎𝑌𝑆
Figure 9 is the log-log plot of the normalized stress-strain data between yield and tensile strength
for the base and weld metal data. Only the portion of the weld metal data following the yield
point elongation was employed in determining the strain hardening exponent, however in order to
account for this strain, the intercept was not set to zero. All of the material parameters for the
weld and base metal samples are summarized in Table 3. In the absence of stress-strain data
associated with the fusion line, the weld metal data was used instead.
Following the instructions provided on September 10 [11], the supplied n values were used in the
subsequent calculations, however the present analysis is preserved in order to highlight the
difference in material fitting constants which can be obtained from the same dataset.
DRDC-RDDC-2015-R156 13
y = 0.0744x
y = 0.0718x
y = 0.1051x - 0.1734
0
0.05
0.1
0.15
0.2
0.25
0 0.5 1 1.5 2 2.5 3 3.5 4
ln(
/Y
S)
ln(E/YS)
Base (W2-Q2)
Base (W2-Q1)
Weld (W2-Strip-1)
Figure 9: Fitting of the strain hardening exponent to the provided stress-strain data.
Table 3: Summary of material parameters.
YS (MPa) TS (MPa) E (GPa) 1/n 1/n Specified [11]
Base Metal 552 653 207 0.073 0.0660
Weld Metal
(HAZ and
Fusion Line)
672 733 207 0.105 0.0422
3.2 Specimen dimensions
As specified in the testing protocol (paragraph 11.1), the physically measured specimen
dimensions, including initial crack length, are summarized in Table 4. The two side-groove (SG)
depths on either side of the specimen were measured from a calibrated digital image acquired on
a stereomicroscope, while the day-light (H) between the grips was acquired by subtracting the
length of the gripped region from the original specimen length. An annotated illustration of the
specimen is shown in Figure 10. The initial crack length (ao) measurement is described in the next
section.
14 DRDC-RDDC-2015-R156
Table 4: Physical specimen measurements
(AWM = All Weld Metal, NCF = Notch Centerline Fusion).
Specimen NOTCH
POSITION W (mm) B
(mm) BN
(mm) H/W a0 (mm) SG1
(mm) SG2
(mm)
Base
A1 Base 14.00 13.99 12.65 9.8 4.91 0.67 0.67
E1 Base 14.03 14.03 12.67 10.2 4.91 0.69 0.67
HI Base 14.01 14.01 12.67 10.1 4.92 0.67 0.68
K1 Base 13.99 14.01 12.69 10.7 4.92 0.66 0.67
W2
A1 AWM 14.17 14.18 12.80 10.1 4.98 0.69 0.69
A2 NCF 14.17 14.18 12.84 10.0 4.98 0.66 0.67
A3 AWM 14.17 14.16 12.79 10.3 4.99 0.69 0.67
A4 NCF 14.17 14.18 12.84 10.0 4.99 0.66 0.67
A5 AWM 14.16 14.19 12.82 10.0 4.98 0.68 0.68
A6 NCF 14.17 14.19 12.83 10.0 4.99 0.70 0.67
A7 NCF 14.17 14.18 12.83 10.4 5.01 0.68 0.67
A8 AWM 14.11 14.11 12.78 8.9 5.06 0.66 0.66
Figure 10: Annotated illustration of the specimen showing the dimensions.
DRDC-RDDC-2015-R156 15
3.3 Physical Crack Length Measurements
Physical crack length measurements were made from the post heat tinted specimens, after they
had been broken open to reveal the extent of ductile crack tearing. The crack length
measurements were made on calibrated digital images captured with a stereo-microscope at 10X
magnification. Both the notch and the crack front were marked with a series of points (barely
visible in Figure 11), with the coordinates exported as an ascii text file. Prior to any
measurements, the image was rotated so that the X-axis of the image was parallel with the
breadth-axis (B) of the specimen. A Matlab function was written which interpolated between the
measurements points at the specified 9 points and reported the average crack length. The output
of the Matlab function file is included within the Annexes for each sample. Note for the cases in
which the sample fractured during testing (A1, E1 and W2-A8), the extent of ductile tearing could
not be ascertained, and no corresponding physical crack length measurements were acquired.
Figure 11: Fracture surface of W2-A1showing the points marking the notch (green)
and extent of ductile crack extensions (red).
3.4 Compliance based crack length estimates
Periodic unloading-reloading elastic compliance cycles were conducted in order to estimate the
crack lengths. Prior to these unloading compliance cycles a 5s displacement controlled hold was
16 DRDC-RDDC-2015-R156
programmed into the control software. As illustrated in Figure 12 this hold resulted in a load
drop, with the lower value defining PU, the load associated with the current compliance cycle, a
value which defined the unloading-reloading minima and maxima loads (PMin and PMax). When
PMax=PU, an undesired plastic CMOD extension was observed, and was eliminated by setting the
maximum cyclic limit to 95% of PU. With PMax=0.95PU, each compliance cycle was elastic, and
repeatable, including a characteristic kink which alternated on either side of the mean compliance
load. The cause of this kink remains inconclusive.
inconclusive.
Figure
PY
LM
Load Drop Associated with 5s hold
PMax = 0.95PU
Pmin = 0.4PU
P Kink in -P
Compliance
Cycles
PU
Figure 12: Elastic unloading-reloading compliance cycles
showing a characteristic kink (Sample W2-A2).
While the analysis software included an option to limit the force-CMOD pairs in the proximity of
the PMax and PMin values, all of the force-CMOD pairs were used in the regression analysis.
Compliance measurements were obtained on each separate unloading and loading segment, with
the mean of all the compliance values being used to calculate the crack lengths. The repeatability
of these compliance based crack length measurements is good; with the mean crack length tightly
bounded within the 95% confidence error limits shown in Figure 13. Even though the
repeatability associated with each individual compliance based measurement is good, there
remains variability between adjacent compliance based measurements. In the case of Sample
W2-A2 shown in Figure 13, the variability is particularly prominent in the first 15 compliance
cycles, prior to the specimen reaching the peak load value which occurs in the vicinity of
compliance cycle 22.
DRDC-RDDC-2015-R156 17
The estimation of the crack length from the unloading-reloading compliance follows the
procedure of Cravero and Ruggieri [3, 12].
Figure 13: Mean and ±95% confidence intervals determined from the compliance based crack
length estimates. Peak load at compliance associated with cycle 22 (Sample W2-A2).
The implication of this variability manifests itself in the determination of a0q based on the least
squares fit of the data corresponding to data beginning with the minimum crack length and ending
at the maximum load. These CTOD-load pairs are fit to the following expression:
𝑎�𝛿 = 𝑎0𝑞 +𝛿
1.4+ 𝐶1𝛿
2 + 𝐶2𝛿3
As seen in Figure 14, the initial variability in the crack length data results in a poor correlation
coefficient (R2) value, which in the case of the data presented in Figure 14, fails the validity
requirements of ASTM E1820 of R2 > 0.96.
18 DRDC-RDDC-2015-R156
Figure 14: Fitting of -a values to determine a0q (Sample W2-A2).
3.5 Fusion line notched specimens – Metallographic Sample Preparation
The four notch centerline fusion specimens were not sectioned to reveal the microstructure
sampled by crack tip. Unfortunately budget and allocated resources were insufficient to complete
this portion of the round-robin. The samples have been returned whole for subsequent analysis.
3.6 Determination of CTOD
3.6.1 Calculation from the double clip gauge
A unique feature of the test protocol was the use of a double clip gauge to estimate the crack
mouth and crack tip opening displacement (CTOD). The double clip gauge CTOD (DCG) was
determined from a triangulation rule according to:
DRDC-RDDC-2015-R156 19
𝛿𝐷𝐶𝐺 = 𝑉1 −ℎ1 + 𝑎0ℎ2 − ℎ1
�𝑉2 − 𝑉1
where the variables h1, h2, V1, V2 and are illustrated in Figure 15. As depicted, the sensitivity of
the double clip gauge technique to measure is improved with increasing amounts of bending.
The crack mouth opening displacement (CMOD) was determined from:
𝐶𝑀𝑂𝐷 = 𝑉1 −ℎ1
ℎ2 − ℎ1�𝑉2 − 𝑉1
As both and CMOD are determined by subtracting quantities, this is a potential for error
propagation. Such error propagation, particularly for small measures of displacement may factor
into the crack length predictions, as these rely on the slope of the CMOD-Force in each loading
and unloading event.
a0
h1
h2
V1
V2
CMOD
Figure 15: Illustration of triangulation scheme used to determine the CTOD (DCG) from
the two crack opening displacement gauges and the offset knife edges.
3.6.2 Calculation of CTOD from J
The determination of the elastic-plastic fracture toughness parameter J follows the formulation
presented in ASTM E1820 which breaks the J-integral into both elastic (Jel) and plastic (Jpl)
components:
𝐽𝑖 = 𝐽𝑒𝑙 ,𝑖 + 𝐽𝑝𝑙 ,𝑖
where the subscript i is an index of the specific unloading-reloading cycle. The elastic component
is given by:
𝐽𝑒𝑙 =𝐾𝑖2�1− 𝜈
𝐸
where 𝐾𝑖 is the elastic stress intensity factor:
20 DRDC-RDDC-2015-R156
𝐾𝑖 = �𝑃𝑖 𝜋𝑎𝑖
�𝐵𝐵𝑁 1/2𝑊 𝐺
𝑎𝑖
𝑊
𝐺 𝑎𝑖
𝑊 = 𝑡𝑗
𝑎𝑖
𝑊
12
𝑗=1
In these expressions is the Poisson Ratio, Pi the load at the i’th unloading-loading compliance
measurement. The constants for the 12th order polynomial defining tj can be obtained from a PRCI
publication [13].
The plastic component given by:
𝐽𝑝𝑙 ,𝑖 = �𝐽𝑝𝑙 ,𝑖−1 +𝜂𝐶𝑀𝑂𝐷 ,𝑖−1
𝑏𝑖−1×
𝐴𝑝𝑙 ,𝑖 − 𝐴𝑝𝑙 ,𝑖−1
𝐵𝑁 �1 −
𝛾𝐿𝐿𝐷,𝑖−1(𝑎𝑖 − 𝑎𝑖−1)
𝑏𝑖−1
where b, the ligament size, is given by (W – a), Apl is the plastic area under the force-CMOD
curve, and the parameters CMOD and LLD have been developed by Finite Element Analysis (FEA)
for a 2-D plane strain assumption[14]. The parameters are expressed as high-degree polynomial
functions of a/W which can also be obtained from the same PCRI publication [13].
The determination of the CTOD from J follows from:
𝛿𝐽 =𝐽
𝑚𝜎𝑌
where m is a third order polynomial based on 1/n. The formulation of the J to CTOD formulation
used in the test protocol is that developed by Shen and Tyson [15]. This formulation has been
reviewed by The Welding Institute (TWI) and found to be in good agreement with the double clip
gauge procedure [7].
DRDC-RDDC-2015-R156 21
4 Results
Table 5 summarizes the mean COD increment (V1), the corresponding elastic loading rate and
the time to reach 0.5Py. In all cases the time to reach 0.5PY is between the stipulated 18 to
180 seconds. The last column is the load drop associated with the termination of the test. Sample
A1 and E1 fractured as a result of an improperly implemented termination sequence which
attempted to hold the partially necked specimen at the interrupt load. However, in the post-necked
state, the specimen is unstable, and fracture ensued. Once this problem was recognized,
subsequent tests unloaded to zero load as soon as the end condition was met. In all but one
specimen, the test terminated after successfully reaching the pre-determined load drop. The
welded sample W2-A8 failed after a load drop of 5.8%. The peak load, PMax, recorded during the
test is also provided in Table 5, as this value effectively discriminates the welded and base metal
samples.
Table 5: Test Conditions.
V1 (mm) Loading
Rate (N/s)
Time to
0.5Py (s) P/PMax – End Condition Pmax (kN)
A1 0.62 737 43 18.7% - Control Error 88.5
E1 0.56 734.3 43.4 14.3% - Control Error 89.2
H1 0.56 736.6 43.1 14.7% - Interrupt 88.1
K1 0.61 739.0 43.0 19.0% - Interrupt 86.7
W2-A1 0.28 550 71.5 13.1% - Interrupt 92.0
W2-A2 0.57 728 53.8 13.3% - Interrupt 94.5
W2-A3 0.501 728 54.1 18.0% - Interrupt 95.3
W2-A4 0.65 715 54.9 17.6% - Interrupt 94.2
W2-A5 0.53 711 55.6 18.2% - Interrupt 92.1
W2-A6 0.63 735.5 52.9 18.6% - Interrupt 95.4
W2-A7 0.63 712.3 56.6 17.6% - Interrupt 95.1
W2-A8 0.32 474.5 82.14 5.8% - Failure 93.6
Table 6 summarizes the crack length data associated with the compliance data (aoq and af) and
physical crack length measurements (a0 and afp). The highlighted cells correspond to the
specimens that used the 60o knife angles, and in all cases the crack lengths failed to satisfy the
validation requirements. Regardless of the knife edges, the estimation procedure used to
determine a0q resulted in poor correlation coefficients as can be seen in the a0q fitting plots
provided for each sample in 0, 0 and 0, for the Base Metal, All Weld Metal and Fusion Line
specimens, respectively.
22 DRDC-RDDC-2015-R156
Table 6: Crack length measurements. Highlighted cell correspond to the specimens
which used a 60o knife edge. af is the calculated crack extension,
while afp is the optically measured crack extension.
Compliance
Measurements
Physical
Measurement
Validations based on
Protocol Para #
aoq af a0 afp 10.4
|aoq-a0|<0.5mm
10.5
af< 0.15afp
A1 5.439 7.404 4.91 NA Invalid Invalid
E1 5.742 7.191 4.91 NA Invalid Invalid
H1 4.962 6.356 5.049 6.577 Valid Invalid
K1 5.558 7.158 5.0245 6.9655 Invalid Invalid
W2-A1 5.050 6.844 5.05 7.246 Valid Invalid
W2-A2 4.972 6.235 5.005 6.508 Valid Invalid
W2-A3 4.989 6.937 5.012 7.284 Valid Valid
W2-A4 4.941 6.559 5.087 6.743 Valid Valid
W2-A5 4.959 7.185 5.015 7.580 Valid Valid
W2-A6 4.987 6.670 5.098 6.810 Valid Valid
W2-A7 4.973 6.555 4.779 7.063 Valid Invalid
W2-A8 5.7171 6.973 5.060 NA Invalid Invalid
Individual sample test sheets which summarize the test parameters, resistance curve data,
estimates of the a0q best fit lines are displayed in Annex C through Annex E. A summary of the
crack growth resistance curves (R curves) are plotted in Figures 16–18 based on CTODJ,
CTODDCG, and J, respectively for all of the data sets whose initial crack length was valid.
The CTODJ-R curves plotted in Figure 16 prominently show three groupings depending on
whether the specimens were associated with the base, weld or notch fusion line. However, when
the same specimens are plotted based on the either the CTODDCG or J-R, only two material
groupings are noted. The samples labelled NCF and Base are grouped together, and separate from
the weld metal samples. This is despite the fact that the maximum loads recorded in Table 5,
clearly differentiate between the welded and base metal samples.
DRDC-RDDC-2015-R156 23
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 0.5 1 1.5 2 2.5
CTO
DJ
(mm
)
a (mm)
H1
A2
A4
A6
A7
A1
A3
A5
A8
Base metal
NCF
Weld Metal
Figure 16: Comparison of the CTODJ-R curves. The three other BM samples were omitted
due to inconsistencies associated with their crack length measurements.
0
0.5
1
1.5
2
2.5
3
0 0.5 1 1.5 2 2.5
CTO
DD
CG
(m
m)
a (mm)
H1
A2
A4
A6
A7
A1
A3
A5
A8
Base metal and NCF
Weld Metal
Figure 17: CTODDCG- R curves.
24 DRDC-RDDC-2015-R156
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 0.5 1 1.5 2 2.5
J(k
J/m
2)
a (mm)
H1
A2
A4
A6
A7
A1
A3
A5
A8
Base metal and NCF
Weld Metal
Figure 18: J-R curve.
A reason for the discrepancy between the CTODJ and CTODDCG is the assumption of flow stress,
and strain hardening exponent n used to compute CTODJ from the J value. In the computation of
the fusion line notched samples, the flow stress (Y) was assumed to be the same as the weld
strength, however given the similarities in the J-R and CTODDCG-R curves, the assumption of the
notched fusion line samples sharing the same strength as the weld centerline samples should be
re-examined.
The fitting parameters and when the data is fit to the following power-law expression are
summarized in Table 7.
𝐶𝑇𝑂𝐷 = 𝛼𝛿�Δ𝑎 𝜂𝛿
DRDC-RDDC-2015-R156 25
Table 7: Power Law Fitting Parameters.
Notch
Location
CTODJR CTODDCG-R
Base Metal A1 1.33 0.51 1.34 0.89
E1 1.49 0.41 1.64 0.67
H1 1.65 0.28 1.82 0.53
K1 1.49 0.20 1.84 0.44
Weld Metal W2-A1 0.98 0.49 1.09 0.76
W2-A3 1.07 0.38 1.28 0.64
W2-A5 0.98 0.40 1.18 0.63
W2-8 1.03 0.56 1.09 0.76
Fusion Line W2-A2 1.41 0.34 1.83 0.54
W2-A4 1.40 0.29 1.84 0.52
W2-6 1.46 0.28 1.86 0.54
W2-7 1.41 0.27 1.87 0.49
26 DRDC-RDDC-2015-R156
5 Conclusion
DRDC tested 12 singled edge notched tension specimens in a 500 kN test frame at room
temperature. Quadruplet specimens with notches positioned in the base metal, fusion line or weld
centerline were tested. Periodic unloading compliance measurements were programmed into a
customized control routine in order to estimate the current crack length. The samples were loaded
until a significant load drop occurred. The crack tip opening displacement (CTOD) was
determined by both a geometrically based Double Clip Gauge (DCG) procedure, or computed
from J.
Significant discrepancies between the CTODJ –R and CTODDCG-R were noted. These
discrepancies were determined to be related to the use of the same Y, and n for both the weld
metal and fusion line. Since the Double Clip Gauge approach does not require an assumption of
the mechanical properties of the given material, it is likely a better approach for heterogeneous
materials or materials with a graded microstructure. Alternatively every effort should be made to
acquire representative hardening and flow stress properties of the material being sampled by the
notch.
The practice of unloading-reloading cycles to estimate compliance based crack length
measurements is not trivial. Despite adjustments to the clip gauges, and ensuring that clip gauges
were properly seated in the knife blocks, negative crack growth was observed in all specimens.
Oscillations in the crack length occurred until the maximum load, after which reliable crack
extension measurements could be made.
DRDC-RDDC-2015-R156 27
6 Recommendations
The following recommendations to the test protocol are suggested:
1. In addition to specifying the angle of the knife edges, the mating groove angles on the
arms of the crack opening displacement gauge also needs to be specified. As a starting
point, the 20-90-70 degree opening angles provided in ASTM E1820 could be
considered, and would provide a complementary configuration to the 60o knife angles.
2. The test procedure should provide guidance on the output of the initial five
unloading-loading compliance measurements specified in Section 8.7.3. It is
recommended that the output of these five cycles be used to compute an estimate of the
crack length which could be compared with optical measurements of the notch length.
3. Methods to approximate the strength of the fusion line need to be addressed.
Consideration for the use of the empirical correlations between hardness and strength
available in the ISO weld fracture toughness standard may be adopted [16].
4. In order to prevent instability in the test frame control procedure, dwell times in the
post-necked configuration need to be minimized. At the end of the test, the standard
should specify that the test frame ramp to zero load, rather than attempt to hold at the
final load.
28 DRDC-RDDC-2015-R156
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DRDC-RDDC-2015-R156 29
References
[1] ISO, Metallic Materials – Method of Constraint Loss Correction of CTOD Fracture
Toughness for Fracture Assessment of Steel Components. 2009, ISO.
[2] Shen, G., Xu, S., and Tyson, W. R., Constraint Effects on Fracture Toughness, DND DREA
CR 2001-091, 2001,
[3] Cravero, S. and Ruggieri, C., Estimation Procedure of J-Resistance Curves for SE(T) Fracture
Specimens Using Unloading Compliance. Engineering Fracture Mechanics, 2007. 74:
p. 2735–2757.
[4] Ruggieri, C., Further Results in J and CTOD Estimation Procedures for SE(T) Fracture
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p. 245–265.
[5] Shen, D. Z., Chyun-Hua, C., and Te-ken, W., Measuring and Calculating CTOD and the
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Evaluating CTOD of SE(T) Specimens in International Pipeline Conference 2014, ASME:
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[7] Moore, P. L. and Pisarski, H. G., Validation of Methods to Determine CTOD from SENT
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[8] Pussegoda, N., Tiku, S., and Tyson, B., Test Protocol: Measurement of Crack Tip Opening
Displacement (CTOD) and J-Fracture Reistance Curves Using Single Edge Notched Tension
(SENT) Specimens, 30166–001 (rev. 01), 2014.
[9] ASTM, Standard Test Method for Measurement of Fracture Toughness, in Metals Test
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[11] Ghovanlou, M., Email to: Christopher Bayley, Standardization of Weld Testing Methods –
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[12] Tyson, W. R., Ding, P., and Wang, X., Elastic Compliance of Single-Edge-Notched Tension
SE(T) (or SENT) Specimens. Frattura e Integrita Strutturale, 2014. 30.
[13] G. Shen, Gianetto, J. A., and Tyson, W. R., Development of Procedure for Low-Constraint
Toughness Testing Using a Single-Specimen Technique, Pipeline Reseach Council
International L52342, 2011.
30 DRDC-RDDC-2015-R156
[14] Lucon, E., Weeks, T. S., Gianetto, J. A., Tyson, W. R., and Park, D. Y., Fracture Toughness
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SE(T) Specimens, in ASTM Committee Week. 2014, ASTM.
[15] Shen, G. and Tyson, W. R. Evaluation of CTOD from J-Integral for SE(T) Specimens. in
Pipeline Technology Conference. Ostend, BE, (2009),
[16] ISO, Metallic Materials - Method of Test for the Determination of Quasistatic Fracture
Toughness of Welds. 2010, BS EN ISO.
[17] ASTM, Standard Practice for Verification of Test Frame and Specimen Alignment under
Tensile and Compressive Axial Force Application, 2005.
.
DRDC-RDDC-2015-R156 31
Annex A Certificates
Figure A.1: Clip Gauge Calibration Certificate.
32 DRDC-RDDC-2015-R156
Figure A.2: Clip Gauge Calibration Certificate.
DRDC-RDDC-2015-R156 33
Figure A.3: Frame 2 Load Cell Calibration Certificate.
34 DRDC-RDDC-2015-R156
Figure A.4: Frame 2 LVDT Calibration Certificate.
DRDC-RDDC-2015-R156 35
Annex B MTS 609 alignment apparatus and 709 alignment software
Alignment performed by: Joel Higgins Equipment: MTS Frame 2 – 641.36 Hydraulic wedge grips Date: 2014/7/23 Thin Rectangular specimen MTS part# 56-651-702, 12 gauge alignment specimen Serial 10388810A Specimen C:\709Align\Specimen\DLP 56-651-702 SN 10388810A.specimen Target Class 5 Target Strain 50 µe Cross Section Type Thin Rectangular Gauge (ohm) 350 Gauge Factor 2.155 Gauge Constant -1856 µe Section Thickness 6.35 mm Rectangular Width 12.7 mm Section Area 80.65 sq mm Distance to Edge 3.175 mm Width Factor 2.000 Elastic Modulus 206.843 GPa Load Factor 0.01668 kN/µe Serial Number 10388810A Material Steel Load at alignment: 5KN Procedure Alignment preformed in accordance with MTS 609/709 alignment practice.
- Specimen installed and gauge offsets measured/recorded. - Initiate alignment wizard in MTS 709 software, and follow onscreen prompts to change
angular and concentric component of the 609 apparatus to remove bending stress from gauged specimen.
Grip information: Rectangular specimen wedges with 6mm backing plates. Validation preformed in accordance to ASTM E1012 [17]
Validation Status: Maximum bending passes 50 micro strain criteria.
36 DRDC-RDDC-2015-R156
Figure B.1: Alignment Output.
DRDC-RDDC-2015-R156 37
Appendix 1 Base Metal
0 0.5 1 1.5 2 2.5-2
0
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
5.4 5.5 5.6 5.7 5.8 5.9 6 6.10
0.2
0.4
0.6
0.8
1
a (mm)
CT
OD
(m
m)
-0.5 0 0.5 1 1.5 20
0.5
1
1.5
2
2.5
a mm
CT
OD
(m
m)
0 10 20 30 40 50 60 70 805
5.5
6
6.5
7
7.5
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.91
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
BM\A1\ Test Date:07/23/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=4.910 a
fp=6.300 a
fp=1.390
Calculated (mm): a0q
=5.419 af=7.338 a
f=1.920
(10.4) a0 Check: a
0-a
0q=-0.50889. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=-0.52953. Requirement: <0.2085
W=14.00 B=13.99 BN
=12.65 mm
Y=602.5
YS=552
T=653 E=207000 (MPa) nu=0.3 n=15.1515
Power Law: CTODJ-R = 1.33 da 0.51 (mm)
Power Law: CTODDCG
-R = 1.41 da 0.82 (mm)
dPdt = 737.3 (N/s) Time to 0.5Py=43.0449 s
Mean V1 Increment=0.61887 mm
0 0.5 1 1.5 2 2.5-2
0
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
5.4 5.5 5.6 5.7 5.8 5.9 6 6.10
0.2
0.4
0.6
0.8
1
a (mm)
CT
OD
(m
m)
-0.5 0 0.5 1 1.5 20
0.5
1
1.5
2
2.5
a mm
CT
OD
(m
m)
0 10 20 30 40 50 60 70 805
5.5
6
6.5
7
7.5
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.91
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
BM\A1\ Test Date:07/23/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=4.910 a
fp=6.300 a
fp=1.390
Calculated (mm): a0q
=5.419 af=7.338 a
f=1.920
(10.4) a0 Check: a
0-a
0q=-0.50889. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=-0.52953. Requirement: <0.2085
W=14.00 B=13.99 BN
=12.65 mm
Y=602.5
YS=552
T=653 E=207000 (MPa) nu=0.3 n=15.1515
Power Law: CTODJ-R = 1.33 da 0.51 (mm)
Power Law: CTODDCG
-R = 1.41 da 0.82 (mm)
dPdt = 737.3 (N/s) Time to 0.5Py=43.0449 s
Mean V1 Increment=0.61887 mm
Figure A1.1: Base Metal A1.
38 DRDC-RDDC-2015-R156
0 0.5 1 1.5 2-2
0
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
5.5 5.6 5.7 5.8 5.9 6 6.10
0.2
0.4
0.6
0.8
a (mm)
CT
OD
(m
m)
-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.60
0.5
1
1.5
2
2.5
a mm
CT
OD
(m
m)
0 10 20 30 40 50 60 705.5
6
6.5
7
7.5
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.77
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
BM\E1\ Test Date:07/24/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=4.910 a
fp=6.300 a
fp=1.390
Calculated (mm): a0q
=5.725 af=7.182 a
f=1.457
(10.4) a0 Check: a
0-a
0q=-0.8149. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=-0.06664. Requirement: <0.2085
W=14.03 B=14.03 BN
=12.67 mm
Y=602.5
YS=552
T=653 E=207000 (MPa) nu=0.3 n=15.1515
Power Law: CTODJ-R = 1.49 da 0.41 (mm)
Power Law: CTODDCG
-R = 1.64 da 0.67 (mm)
dPdt = 734.3 (N/s) Time to 0.5Py=43.4307 s
Mean V1 Increment=0.56257 mm
Figure A1.2: Base Metal E1.
DRDC-RDDC-2015-R156 39
0 0.5 1 1.5 2-2
0
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
4.9 4.95 5 5.05 5.1 5.150
0.2
0.4
0.6
0.8
1
a (mm)
CT
OD
(m
m)
-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.40
0.5
1
1.5
2
2.5
a mm
CT
OD
(m
m)
0 10 20 30 40 50 60 704.5
5
5.5
6
6.5
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.57
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
BM\H1\ Test Date:08/06/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=5.049 a
fp=6.577 a
fp=1.528
Calculated (mm): a0q
=4.965 af=6.361 a
f=1.396
(10.4) a0 Check: a
0-a
0q=0.084369. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=0.13193. Requirement: <0.22924
W=14.01 B=14.01 BN
=12.67 mm
Y=602.5
YS=552
T=653 E=207000 (MPa) nu=0.3 n=15.1515
Power Law: CTODJ-R = 1.65 da 0.28 (mm)
Power Law: CTODDCG
-R = 1.82 da 0.53 (mm)
dPdt = 736.6 (N/s) Time to 0.5Py=42.5397 s
Mean V1 Increment=0.55558 mm
Figure A1.3: Base Metal H1.
40 DRDC-RDDC-2015-R156
0 2 4 6 8 10 12 14
5
5.2
5.4
5.6
5.8
6
6.2
6.4
6.6
6.8
mm
mm
BM\H1\ Test Date:08/06/2014 Temp:20 C
Analysis Date:21-Aug-2014
W=14.01mmB
N=12.67mm
afp
=6.5774mm
a0=5.0491mm
ap=1.5283mm
X (mm) Y (mm) X (mm) Y (mm)0.883243 6.06703 0.133691 4.90777 2.26142 6.45096 1.70102 5.05007 3.63959 6.63217 3.26835 5.10237 5.01776 6.71512 4.83568 5.07224 6.39594 6.75799 6.40301 5.06333 7.77411 6.71768 7.97034 5.07928 9.15229 6.69715 9.53767 5.07633 10.5305 6.51035 11.105 5.05157 11.9086 6.20855 12.6723 4.8871
Crack Validation
(10.2.a) Not Applicable as No Fatigue Crack(10.2.b) Crack Curvature Okay (0.51037) mm Less than (7.005 )
Figure A1.4: Base Metal H1 – Crack Length.
DRDC-RDDC-2015-R156 41
0 0.5 1 1.5 2 2.5-2
0
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
5.35 5.4 5.45 5.5 5.55 5.6 5.65 5.7 5.75 5.80
0.2
0.4
0.6
0.8
a (mm)
CT
OD
(m
m)
-0.5 0 0.5 1 1.5 20
0.5
1
1.5
2
2.5
a mm
CT
OD
(m
m)
0 20 40 60 80 1005
5.5
6
6.5
7
7.5
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.61
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
BM\K1\ Test Date:07/23/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=5.024 a
fp=6.965 a
fp=1.941
Calculated (mm): a0q
=5.563 af=7.164 a
f=1.601
(10.4) a0 Check: a
0-a
0q=-0.53843. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=0.34007. Requirement: <0.29115
W=13.99 B=14.01 BN
=12.69 mm
Y=602.5
YS=552
T=653 E=207000 (MPa) nu=0.3 n=15.1515
Power Law: CTODJ-R = 1.49 da 0.20 (mm)
Power Law: CTODDCG
-R = 1.84 da 0.44 (mm)
dPdt = 739.0 (N/s) Time to 0.5Py=42.4914 s
Mean V1 Increment=0.60531 mm
Figure A1.5: Base Metal K1.
42 DRDC-RDDC-2015-R156
0 2 4 6 8 10 12 144.5
5
5.5
6
6.5
7
7.5
mm
mm
BM\K1\ Test Date:07/23/2014 Temp:20 C
Analysis Date:21-Aug-2014
W=13.99mmB
N=12.69mm
afp
=6.9655mm
a0=5.0245mm
ap=1.9409mm
X (mm) Y (mm) X (mm) Y (mm)0.911428 6.86738 0.119449 4.92761 2.28609 6.87005 1.69034 5.0308 3.66075 7.01864 3.26123 5.06511 5.03542 7.08519 4.83212 5.07008 6.41008 7.12074 6.40301 5.06875 7.78474 7.08833 7.9739 5.02948 9.15941 7.01409 9.54479 5.01312 10.5341 6.86117 11.1157 5.01209 11.9087 6.46376 12.6866 4.88593
Crack Validation
(10.2.a) Not Applicable as No Fatigue Crack(10.2.b) Crack Curvature Okay (0.50171) mm Less than (6.995 )
Figure A1.6: Base Metal K1 – Crack Lengths.
DRDC-RDDC-2015-R156 43
Appendix 2 All Weld Metal
0 0.5 1 1.5 2-2
0
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
3.5 4 4.5 5 5.5 60
0.1
0.2
0.3
0.4
0.5
0.6
0.7
a (mm)
CT
OD
(m
m)
-1.5 -1 -0.5 0 0.5 1 1.5 20
0.5
1
1.5
2
a mm
CT
OD
(m
m)
0 20 40 60 80 100 120 1402
3
4
5
6
7
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.15
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
AWM\A1\ Test Date:08/06/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=5.050 a
fp=7.246 a
fp=2.196
Calculated (mm): a0q
=5.085 af=6.864 a
f=1.779
(10.4) a0 Check: a
0-a
0q=-0.034989. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=0.41735. Requirement: <0.3294
W=14.17 B=14.18 BN
=12.84 mm
Y=702.5
YS=672
T=733 E=207000 (MPa) nu=0.3 n=23.6967
Power Law: CTODJ-R = 0.98 da 0.49 (mm)
Power Law: CTODDCG
-R = 1.10 da 0.76 (mm)
dPdt = 550.1 (N/s) Time to 0.5Py=71.5306 s
Mean V1 Increment=0.3039 mm
0 0.5 1 1.5 2-2
0
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
3.5 4 4.5 5 5.5 60
0.1
0.2
0.3
0.4
0.5
0.6
0.7
a (mm)
CT
OD
(m
m)
-1.5 -1 -0.5 0 0.5 1 1.5 20
0.5
1
1.5
2
a mm
CT
OD
(m
m)
0 20 40 60 80 100 120 1402
3
4
5
6
7
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.15
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
AWM\A1\ Test Date:08/06/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=5.050 a
fp=7.246 a
fp=2.196
Calculated (mm): a0q
=5.085 af=6.864 a
f=1.779
(10.4) a0 Check: a
0-a
0q=-0.034989. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=0.41735. Requirement: <0.3294
W=14.17 B=14.18 BN
=12.84 mm
Y=702.5
YS=672
T=733 E=207000 (MPa) nu=0.3 n=23.6967
Power Law: CTODJ-R = 0.98 da 0.49 (mm)
Power Law: CTODDCG
-R = 1.10 da 0.76 (mm)
dPdt = 550.1 (N/s) Time to 0.5Py=71.5306 s
Mean V1 Increment=0.3039 mm
Figure A2.1: All Weld Metal W2-A1.
44 DRDC-RDDC-2015-R156
0 2 4 6 8 10 12 145
5.5
6
6.5
7
7.5
8
mm
mm
AWM\A1\ Test Date:08/06/2014 Temp:20 C
Analysis Date:21-Aug-2014
W=14.17mmB
N=12.84mm
afp
=7.2458mm
a0=5.0534mm
ap=2.1924mm
X (mm) Y (mm) X (mm) Y (mm)0.721404 7.12624 0.120349 5.047 2.17097 7.13123 1.71842 5.02765 3.62054 7.36521 3.31648 5.05754 5.07011 7.38371 4.91455 5.06301 6.51969 7.45937 6.51261 5.04997 7.96926 7.36589 8.11068 5.06578 9.41883 7.24161 9.70875 5.04887 10.8684 7.04722 11.3068 5.05914 12.318 6.81761 12.9049 5.06301
Crack Validation
(10.2.a) Not Applicable as No Fatigue Crack(10.2.b) Crack Curvature Okay (0.42816) mm Less than (7.085 )
Figure A2.2: All Weld Metal W2-A1 – Crack Lengths.
DRDC-RDDC-2015-R156 45
0 0.5 1 1.5 20
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
4.96 4.98 5 5.02 5.04 5.06 5.08 5.1 5.12 5.140
0.1
0.2
0.3
0.4
0.5
0.6
0.7
a (mm)
CT
OD
(m
m)
-0.5 0 0.5 1 1.5 20
0.5
1
1.5
2
a mm
CT
OD
(m
m)
0 5 10 15 20 25 30 35 404.5
5
5.5
6
6.5
7
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.17
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
AWM\A3\ Test Date:08/18/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=5.012 a
fp=7.284 a
fp=2.272
Calculated (mm): a0q
=5.008 af=6.915 a
f=1.907
(10.4) a0 Check: a
0-a
0q=0.003481. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=0.36561. Requirement: <0.34084
W=14.17 B=14.16 BN
=12.79 mm
Y=703.5
YS=674
T=733 E=207000 (MPa) nu=0.3 n=23.6967
Power Law: CTODJ-R = 1.07 da 0.38 (mm)
Power Law: CTODDCG
-R = 1.28 da 0.64 (mm)
dPdt = 728.7 (N/s) Time to 0.5Py=54.1681 s
Mean V1 Increment=0.50979 mm
Figure A2.3: All Weld Metal W2-A3.
46 DRDC-RDDC-2015-R156
0 2 4 6 8 10 12 144.5
5
5.5
6
6.5
7
7.5
mm
mm
AWM\A3\ Test Date:08/18/2014 Temp:20 C
Analysis Date:21-Aug-2014
W=14.17mmB
N=12.79mm
afp
=7.2841mm
a0=5.0118mm
ap=2.2724mm
X (mm) Y (mm) X (mm) Y (mm)0.749689 6.88036 0.12742 4.94715 2.16037 7.19618 1.69367 5.00186 3.57105 7.3681 3.25991 5.02058 4.98172 7.45309 4.82616 5.03102 6.3924 7.46406 6.3924 5.02152 7.80308 7.4334 7.95865 5.0188 9.21376 7.35677 9.52489 5.02235 10.6244 7.15524 11.0911 5.01535 12.0351 6.81201 12.6574 4.97815
Crack Validation
(10.2.a) Not Applicable as No Fatigue Crack(10.2.b) Crack Curvature Okay (0.47212) mm Less than (7.085 )
Figure A2.4: All Weld Metal W2-A3 – Crack Lengths.
DRDC-RDDC-2015-R156 47
0 0.5 1 1.5 20
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
4.9 5 5.1 5.2 5.3 5.4 5.50
0.1
0.2
0.3
0.4
0.5
0.6
0.7
a (mm)
CT
OD
(m
m)
0 0.5 1 1.5 2 2.50
0.5
1
1.5
2
a mm
CT
OD
(m
m)
0 5 10 15 20 25 30 35 404.5
5
5.5
6
6.5
7
7.5
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.92
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
AWM\A5\ Test Date:08/18/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=5.015 a
fp=7.580 a
fp=2.566
Calculated (mm): a0q
=4.988 af=7.183 a
f=2.195
(10.4) a0 Check: a
0-a
0q=0.026626. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=0.37053. Requirement: <0.38488
W=14.16 B=14.19 BN
=12.82 mm
Y=703.5
YS=674
T=733 E=207000 (MPa) nu=0.3 n=23.6967
Power Law: CTODJ-R = 0.98 da 0.40 (mm)
Power Law: CTODDCG
-R = 1.18 da 0.63 (mm)
dPdt = 711.1 (N/s) Time to 0.5Py=55.5608 s
Mean V1 Increment=0.53325 mm
Figure A2.5: All Weld Metal W2-A5.
48 DRDC-RDDC-2015-R156
0 2 4 6 8 10 12 144.5
5
5.5
6
6.5
7
7.5
8
mm
mm
AWM\A5\ Test Date:08/18/2014 Temp:20 C
Analysis Date:21-Aug-2014
W=14.16mmB
N=12.82mm
afp
=7.5805mm
a0=5.0146mm
ap=2.5659mm
X (mm) Y (mm) X (mm) Y (mm)0.784995 7.5578 0.148584 4.99798 2.21336 7.38211 1.73429 4.99487 3.64173 7.57734 3.31999 5.02578 5.0701 7.73873 4.9057 5.01124 6.49847 7.64401 6.4914 5.02624 7.92684 7.62987 8.0771 5.01606 9.35521 7.70261 9.66281 5.02476 10.7836 7.47274 11.2485 5.02262 12.2119 7.43535 12.8342 4.99173
Crack Validation
(10.2.a) Not Applicable as No Fatigue Crack(10.2.b) Crack Curvature Okay (0.19839) mm Less than (7.08 )
Figure A2.6: All Weld Metal W2-A5 – Crack Lengths.
DRDC-RDDC-2015-R156 49
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.60
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
5.6 5.7 5.8 5.9 6 6.1 6.2 6.30
0.1
0.2
0.3
0.4
0.5
0.6
0.7
a (mm)
CT
OD
(m
m)
-0.2 0 0.2 0.4 0.6 0.8 1 1.20
0.2
0.4
0.6
0.8
1
1.2
1.4
a mm
CT
OD
(m
m)
0 2 4 6 8 10 12 14 16 185.5
6
6.5
7
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.84
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
AWM\A8\ Test Date:07/23/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=5.060 a
fp=6.300 a
fp=1.240
Calculated (mm): a0q
=5.710 af=6.909 a
f=1.199
(10.4) a0 Check: a
0-a
0q=-0.65044. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=0.041467. Requirement: <0.186
W=14.11 B=14.11 BN
=12.78 mm
Y=703.5
YS=674
T=733 E=207000 (MPa) nu=0.3 n=23.6967
Power Law: CTODJ-R = 1.03 da 0.56 (mm)
Power Law: CTODDCG
-R = 1.09 da 0.76 (mm)
dPdt = 474.5 (N/s) Time to 0.5Py=82.14 s
Mean V1 Increment=0.31612 mm
Figure A2.7: All Weld Metal W2-A8.
50 DRDC-RDDC-2015-R156
Appendix 3 Notch Center Fusion Line
0 0.5 1 1.5 2-2
0
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
4.96 4.98 5 5.02 5.04 5.06 5.08 5.1 5.12 5.140
0.2
0.4
0.6
0.8
a (mm)
CT
OD
(m
m)
-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.40
0.5
1
1.5
2
2.5
a mm
CT
OD
(m
m)
0 5 10 15 20 25 30 35 40 454.5
5
5.5
6
6.5
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.18
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
AWM\A2\ Test Date:07/23/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=5.005 a
fp=6.508 a
fp=1.503
Calculated (mm): a0q
=4.986 af=6.265 a
f=1.279
(10.4) a0 Check: a
0-a
0q=0.018603. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=0.22476. Requirement: <0.2255
W=14.11 B=14.11 BN
=12.78 mm
Y=703.5
YS=674
T=733 E=207000 (MPa) nu=0.3 n=23.6967
Power Law: CTODJ-R = 1.41 da 0.34 (mm)
Power Law: CTODDCG
-R = 1.83 da 0.54 (mm)
dPdt = 728.2 (N/s) Time to 0.5Py=53.8496 s
Mean V1 Increment=0.57002 mm
0 0.5 1 1.5 2-2
0
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
4.96 4.98 5 5.02 5.04 5.06 5.08 5.1 5.12 5.140
0.2
0.4
0.6
0.8
a (mm)
CT
OD
(m
m)
-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.40
0.5
1
1.5
2
2.5
a mm
CT
OD
(m
m)
0 5 10 15 20 25 30 35 40 454.5
5
5.5
6
6.5
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.18
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
AWM\A2\ Test Date:07/23/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=5.005 a
fp=6.508 a
fp=1.503
Calculated (mm): a0q
=4.986 af=6.265 a
f=1.279
(10.4) a0 Check: a
0-a
0q=0.018603. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=0.22476. Requirement: <0.2255
W=14.11 B=14.11 BN
=12.78 mm
Y=703.5
YS=674
T=733 E=207000 (MPa) nu=0.3 n=23.6967
Power Law: CTODJ-R = 1.41 da 0.34 (mm)
Power Law: CTODDCG
-R = 1.83 da 0.54 (mm)
dPdt = 728.2 (N/s) Time to 0.5Py=53.8496 s
Mean V1 Increment=0.57002 mm
Figure A3.1: Notch Fusion Line W2-A2.
DRDC-RDDC-2015-R156 51
0 2 4 6 8 10 12 14
5
5.2
5.4
5.6
5.8
6
6.2
6.4
6.6
6.8
mm
mm
AWM\A2\ Test Date:07/23/2014 Temp:20 C
Analysis Date:21-Aug-2014
W=14.11mmB
N=12.78mm
afp
=6.5083mm
a0=5.0052mm
ap=1.5031mm
X (mm) Y (mm) X (mm) Y (mm)1.01103 5.93031 0.155405 4.97207 2.3714 6.37775 1.73764 5.003143.73177 6.58665 3.31987 5.002125.09214 6.70377 4.9021 5.027656.45251 6.73338 6.48433 5.01727.81288 6.7097 8.06656 4.999379.17325 6.62273 9.64879 5.0053110.5336 6.37735 11.231 5.02353 11.894 5.98052 12.8133 4.95525
Crack Validation
(10.2.a) Not Applicable as No Fatigue Crack(10.2.b) Crack Curvature Okay (0.57804) mm Less than (7.055 )
Figure A3.2: Notch Fusion Line W2-A2 – Crack Lengths.
52 DRDC-RDDC-2015-R156
0 0.5 1 1.5 2 2.50
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
4.95 5 5.05 5.1 5.15 5.2 5.250
0.2
0.4
0.6
0.8
1
a (mm)
CT
OD
(m
m)
-0.5 0 0.5 1 1.5 20
0.5
1
1.5
2
2.5
a mm
CT
OD
(m
m)
0 5 10 15 20 25 30 35 40 454.5
5
5.5
6
6.5
7
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.51
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
AWM\A4\ Test Date:08/18/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=5.087 a
fp=6.743 a
fp=1.657
Calculated (mm): a0q
=4.968 af=6.584 a
f=1.616
(10.4) a0 Check: a
0-a
0q=0.11815. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=0.041238. Requirement: <0.24852
W=14.17 B=14.18 BN
=12.84 mm
Y=703.5
YS=674
T=733 E=207000 (MPa) nu=0.3 n=23.6967
Power Law: CTODJ-R = 1.40 da 0.29 (mm)
Power Law: CTODDCG
-R = 1.84 da 0.52 (mm)
dPdt = 715.5 (N/s) Time to 0.5Py=54.9302 s
Mean V1 Increment=0.65427 mm
Figure A3.3: Notch Fusion Line W2-A4.
DRDC-RDDC-2015-R156 53
0 2 4 6 8 10 12 144.5
5
5.5
6
6.5
7
7.5
mm
mm
AWM\A4\ Test Date:08/18/2014 Temp:20 C
Analysis Date:21-Aug-2014
W=14.17mmB
N=12.84mm
afp
=6.7434mm
a0=5.0866mm
ap=1.6568mm
X (mm) Y (mm) X (mm) Y (mm)0.990111 6.17772 0.134491 4.97733 2.35483 6.55825 1.72725 5.06789 3.71954 6.8282 3.32002 5.06229 5.08426 6.98639 4.91278 5.10051 6.44897 7.00617 6.50554 5.12665 7.81369 6.98712 8.09831 5.12665 9.1784 6.83726 9.69107 5.11355 10.5431 6.6115 11.2838 5.11988 11.9078 6.08699 12.8766 4.97361
Crack Validation
(10.2.a) Not Applicable as No Fatigue Crack(10.2.b) Crack Curvature Okay (0.65641) mm Less than (7.085 )
Figure A3.4: Notch Fusion Line W2-A4 – Crack Lengths.
54 DRDC-RDDC-2015-R156
0 0.5 1 1.5 2 2.50
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
5 5.05 5.1 5.15 5.2 5.25 5.30
0.2
0.4
0.6
0.8
1
a (mm)
CT
OD
(m
m)
-0.5 0 0.5 1 1.5 20
0.5
1
1.5
2
2.5
a mm
CT
OD
(m
m)
0 10 20 30 40 504.5
5
5.5
6
6.5
7
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.68
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
AWM\A6\ Test Date:08/18/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=5.098 a
fp=6.810 a
fp=1.712
Calculated (mm): a0q
=5.006 af=6.659 a
f=1.654
(10.4) a0 Check: a
0-a
0q=0.0916. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=0.058766. Requirement: <0.25684
W=14.10 B=14.19 BN
=12.83 mm
Y=703.5
YS=674
T=733 E=207000 (MPa) nu=0.3 n=23.6967
Power Law: CTODJ-R = 1.46 da 0.28 (mm)
Power Law: CTODDCG
-R = 1.86 da 0.54 (mm)
dPdt = 735.5 (N/s) Time to 0.5Py=52.9245 s
Mean V1 Increment=0.62949 mm
Figure A3.5: Notch Fusion Line W2-A6.
DRDC-RDDC-2015-R156 55
0 2 4 6 8 10 12 144.5
5
5.5
6
6.5
7
7.5
mm
mm
AWM\A6\ Test Date:08/18/2014 Temp:20 C
Analysis Date:21-Aug-2014
W=14.1mmB
N=12.83mm
afp
=6.8098mm
a0=5.0975mm
ap=1.7123mm
X (mm) Y (mm) X (mm) Y (mm)1.21604 6.21473 0.162426 4.94981 2.5446 6.6406 1.74113 5.079023.87317 6.90773 3.31984 5.117155.20173 7.03042 4.89855 5.126656.53029 7.0741 6.47726 5.139947.85885 7.04905 8.05597 5.143399.18742 6.94255 9.63467 5.11078 10.516 6.66452 11.2134 5.1025411.8445 6.12485 12.7921 4.97183
Crack Validation
(10.2.a) Not Applicable as No Fatigue Crack(10.2.b) Crack Curvature Okay (0.685) mm Less than (7.05 )
Figure A3.6: Notch Fusion Line W2-A6 – Crack Lengths.
56 DRDC-RDDC-2015-R156
0 0.5 1 1.5 2 2.5-2
0
2
4
6
8
10x 10
4
CMOD (mm)
Fo
rce
(N
)
4.95 5 5.05 5.1 5.15 5.2 5.250
0.2
0.4
0.6
0.8
a (mm)
CT
OD
(m
m)
-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.60
0.5
1
1.5
2
2.5
a mm
CT
OD
(m
m)
0 5 10 15 20 25 30 35 40 454.5
5
5.5
6
6.5
7
Index
a (
mm
)
CMODLmPy
a0q
Fit R2=0.41
CTOD
CTODmin
CTODJ
CTODDCG
aMean
a+-95%
AWM\A7\ Test Date:08/18/2014 Temp:20 C
Analysis Date:15-Sep-2014
Crack Length Data - Based on All Unloading-Loading Curves
Measure (mm): a0=4.779 a
fp=7.063 a
fp=2.284
Calculated (mm): a0q
=5.004 af=6.579 a
f=1.575
(10.4) a0 Check: a
0-a
0q=-0.22526. Requirement: <0.5mm
(10.5) afp
Check: afp
-af=0.70942. Requirement: <0.34262
W=14.10 B=14.18 BN
=12.83 mm
Y=703.5
YS=674
T=733 E=207000 (MPa) nu=0.3 n=23.6967
Power Law: CTODJ-R = 1.41 da 0.27 (mm)
Power Law: CTODDCG
-R = 1.87 da 0.49 (mm)
dPdt = 712.3 (N/s) Time to 0.5Py=56.583 s
Mean V1 Increment=0.62972 mm
Figure A3.7: Notch Fusion Line W2-A7.
DRDC-RDDC-2015-R156 57
0 2 4 6 8 10 12 144.5
5
5.5
6
6.5
7
7.5
mm
mm
AWM\A7\ Test Date:08/18/2014 Temp:20 C
Analysis Date:21-Aug-2014
W=14.1mmB
N=12.83mm
afp
=7.0627mm
a0=4.7786mm
ap=2.2841mm
X (mm) Y (mm) X (mm) Y (mm)1.03219 6.81312 0.105856 4.847872.39257 6.85775 1.6828 4.790853.75296 7.16195 3.25974 4.77375.11334 7.31993 4.83668 4.766026.47372 7.32581 6.41362 4.766027.83411 7.2692 7.99056 4.766029.19449 7.0899 9.5675 4.7721410.5549 6.87112 11.1444 4.7801611.9153 6.39828 12.7214 4.78016
Crack Validation
(10.2.a) Not Applicable as No Fatigue Crack(10.2.b) Crack Curvature Okay (0.66439) mm Less than (7.05 )
Figure A3.8: Notch Fusion Line W2-A7 – Crack Lengths.
58 DRDC-RDDC-2015-R156
This page intentionally left blank.
DRDC-RDDC-2015-R156 59
List of symbols/abbreviations/acronyms/initialisms
a Crack length
a0q Calculated Initial crack length
af Calculated final crack length
a0 Optically measured initial crack length
afp Optically measured final crack length
af Calculated crack extension
afp Optically measured crack extension
b Ligament length (W-a)
B Specimen Breadth
BN Specimen Breadth at notches
CMOD (m) Crack Mouth Opening Displacement
CTODDCG (DCG) Crack Tip Opening Displacement from Double Clip Gauge
CTODJ (J) CTOD converted from J Integral
CTODDCG CTOD determined from Double Clip Gauges
E Modulus of elasticity
G Shape correction for stress intensity factor calculation
i Index to denote the unloading-reloading compliance cycle
Poisson Ratio
Eta factor for determination of Jpl
h1 and h2 Height of the knife edges
H “Day Light” between grips
J Elastic-Plastic Fracture Toughness parameter
K Stress intensity factor
LM Estimated maximum load (LM=(W-a0)BTS)
n Strain hardening exponent
SG1 and SG2 Depth of the side grooves
Y Flow stress (average of yield and tensile strength)
YS 0.2% offset Yield Strength
TS Tensile strength
PY Yield point load
PU Load at onset of compliance cycle
PMAX Maximum Load associated with compliance cycles
PMIN Minimum Load associated with compliance cycles
P Load Range associated with compliance cycle
V1 and V2 Opening displacements of the COD gauges
W Specimen Width in direction of crack propagation
60 DRDC-RDDC-2015-R156
This page intentionally left blank.
DOCUMENT CONTROL DATA (Security markings for the title, abstract and indexing annotation must be entered when the document is Classified or Designated)
1. ORIGINATOR (The name and address of the organization preparing the document.
Organizations for whom the document was prepared, e.g., Centre sponsoring a
contractor's report, or tasking agency, are entered in Section 8.)
DRDC – Atlantic Research Centre Defence Research and Development Canada 9 Grove Street P.O. Box 1012 Dartmouth, Nova Scotia B2Y 3Z7 Canada
2a. SECURITY MARKING (Overall security marking of the document including
special supplemental markings if applicable.)
UNCLASSIFIED
2b. CONTROLLED GOODS
(NON-CONTROLLED GOODS) DMC A REVIEW: GCEC DECEMBER 2012
3. TITLE (The complete document title as indicated on the title page. Its classification should be indicated by the appropriate abbreviation (S, C or U) in
parentheses after the title.)
Evaluation of the single edge notch tension specimen for quantifying fracture toughness : Participation in a round-robin test program
4. AUTHORS (last name, followed by initials – ranks, titles, etc., not to be used)
Bayley, C.
5. DATE OF PUBLICATION (Month and year of publication of document.)
August 2015
6a. NO. OF PAGES
(Total containing information,
including Annexes, Appendices,
etc.)
70
6b. NO. OF REFS
(Total cited in document.)
17
7. DESCRIPTIVE NOTES (The category of the document, e.g., technical report, technical note or memorandum. If appropriate, enter the type of report,
e.g., interim, progress, summary, annual or final. Give the inclusive dates when a specific reporting period is covered.)
Scientific Report
8. SPONSORING ACTIVITY (The name of the department project office or laboratory sponsoring the research and development – include address.)
DRDC – Atlantic Research Centre Defence Research and Development Canada 9 Grove Street P.O. Box 1012 Dartmouth, Nova Scotia B2Y 3Z7 Canada
9a. PROJECT OR GRANT NO. (If appropriate, the applicable research
and development project or grant number under which the document
was written. Please specify whether project or grant.)
9b. CONTRACT NO. (If appropriate, the applicable number under
which the document was written.)
10a. ORIGINATOR’S DOCUMENT NUMBER (The official document
number by which the document is identified by the originating
activity. This number must be unique to this document.)
DRDC-RDDC-2015-R156
10b. OTHER DOCUMENT NO(s). (Any other numbers which may be
assigned this document either by the originator or by the sponsor.)
11. DOCUMENT AVAILABILITY (Any limitations on further dissemination of the document, other than those imposed by security classification.)
Unlimited
12. DOCUMENT ANNOUNCEMENT (Any limitation to the bibliographic announcement of this document. This will normally correspond to the
Document Availability (11). However, where further distribution (beyond the audience specified in (11) is possible, a wider announcement
audience may be selected.))
Unlimited
13. ABSTRACT (A brief and factual summary of the document. It may also appear elsewhere in the body of the document itself. It is highly desirable that
the abstract of classified documents be unclassified. Each paragraph of the abstract shall begin with an indication of the security classification of the
information in the paragraph (unless the document itself is unclassified) represented as (S), (C), (R), or (U). It is not necessary to include here abstracts in
both official languages unless the text is bilingual.)
DRDC was asked to participate in a round-robin program investigating a new test protocol to
measure the fracture toughness of steels and welds. The round-robin program utilized a testing
procedure being examined by the Pipeline Research Council International using a single edge
notch tension (SENT) specimen, rather than the more conventional single edge bend specimen.
Twelve SENT specimens were tested in a 500 kN test frame at room temperature with notches
located in either the base metal, fusion line or weld centerline. Periodic unloading compliance
measurements were programmed into a customized control routine in order to estimate the crack
length throughout the test duration. At each unloading point, the crack tip opening displacement
(CTOD) was determined by either a geometrically based Double Clip Gauge (DCG) procedure,
or computed from the elastic plastic fracture toughness parameter J. Tearing resistance curves
were computed, with significant discrepancies noted between the two different fracture
toughness measurement approaches. The most striking difference was associated with the fusion
line specimens, and was attributed to invalid material constants. Since the DCG approach does
not require an assumption of the mechanical properties of the given material, it is likely a better
approach for heterogeneous materials or when the notch is located within a graded
microstructure.
---------------------------------------------------------------------------------------------------------------
On a demandé à RDDC de participer à un programme visant l’étude, à tour de rôle, d’un
nouveau protocole d’essai élaboré pour mesurer la ténacité à la rupture d’aciers et de soudures.
Le programme reposait sur une procédure d’essai étudiée par Pipeline Research Council
International au moyen d’une éprouvette de traction entaillée d’un côté (ETEUC), plutôt que
d’une éprouvette de flexion plus classique entaillée d’un côté.
Douze ETEUC ont été éprouvées dans un bâti d’essai de 500 kN, à la température ambiante,
après avoir été entaillées dans le métal de base, dans la ligne de fusion ou dans l’axe de soudure.
Des mesures périodiques de conformité et de décharge ont été programmées dans une routine de
contrôle personnalisée pour estimer la longueur de fissuration tout au long de l’essai. Le
déplacement de l’extrémité de fissure a été déterminé à chaque point de décharge en suivant une
procédure géométrique impliquant l’utilisation d’une jauge à pince double ou en le calculant
d’après le paramètre J de ténacité à la rupture plastique et élastique. Après le calcul de courbes
de ténacité, d’importantes anomalies on été relevées entre les deux approches distinctes de
mesure de la ténacité, la plus marquée étant associée aux éprouvettes de ligne de fusion et
attribuée à des constantes de matière invalides. L’approche impliquant l’utilisation d’une jauge
à pince double se prête probablement mieux aux matières hétérogènes ou aux entailles situées
dans une microstructure stratifiée, car elle n’exige aucune présomption des propriétés
mécaniques d’une matière donnée.
14. KEYWORDS, DESCRIPTORS or IDENTIFIERS (Technically meaningful terms or short phrases that characterize a document and could be helpful
in cataloguing the document. They should be selected so that no security classification is required. Identifiers, such as equipment model designation,
trade name, military project code name, geographic location may also be included. If possible keywords should be selected from a published thesaurus,
e.g., Thesaurus of Engineering and Scientific Terms (TEST) and that thesaurus identified. If it is not possible to select indexing terms which are
Unclassified, the classification of each should be indicated as with the title.)
Fracture Mechanics; Steel