Evaluation of the single edge notch tension specimen for ...cradpdf.drdc-rddc.gc.ca/PDFS/unc203/p802059_A1b.pdf · specimen for quantifying fracture toughness Participation in a round-robin

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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 A3.1: Notch Fusion Line W2-A2. . . . . . . . . . . . . . . . . . . . . . 50

Figure A3.2: Notch Fusion Line W2-A2 – Crack Lengths. . . . . . . . . . . . . . . 51







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.


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.


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


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.


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


Figure 5: Custom designed knife blocks.


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.


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


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.


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









6.0 Ramp to 100% of Load

6.5 1 s Force control hold


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.


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.


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.


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


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.


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.


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:


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:


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].


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.


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.


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.


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


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


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.


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.


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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

Specimens – Part I: Homogeneous Materials. Engineering Fracture Mechanics, 2012. 79:

p. 245–265.

[5] Shen, D. Z., Chyun-Hua, C., and Te-ken, W., Measuring and Calculating CTOD and the

J·Integral with a Double Clip Gauge. Strain, 1980. 16(2): p. 63–67.

[6] Zijian Yan, Yifan Huang, and Zhou, W., Accuracy of the Double-Clip on Gauge Method for

Evaluating CTOD of SE(T) Specimens in International Pipeline Conference 2014, ASME:

Calgary, AB.

[7] Moore, P. L. and Pisarski, H. G., Validation of Methods to Determine CTOD from SENT

Specimens, in The 22nd International Ocean and Polar Engineering Conference 2012: Rhodes

(Rodos), Greece.

[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

Methods and Analytical Procedures. 2011, ASTM: USA.

[10] Kandil, F., A Procedure for the Measurement of Machine Alignment in Axial Testing,

VAMAS 42, 2001.

[11] Ghovanlou, M., Email to: Christopher Bayley, Standardization of Weld Testing Methods –

Single Edge Notched Test (SENT) Fracture Toughness Measurements, Sept 10, 2014.

[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.


[14] Lucon, E., Weeks, T. S., Gianetto, J. A., Tyson, W. R., and Park, D. Y., Fracture Toughness

Characterization of High-Pressure Pipe Girth Welds Using Single-Edge Notched Tension

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.

.


Annex A Certificates

Figure A.1: Clip Gauge Calibration Certificate.


Figure A.2: Clip Gauge Calibration Certificate.


Figure A.3: Frame 2 Load Cell Calibration Certificate.


Figure A.4: Frame 2 LVDT Calibration Certificate.


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.


Figure B.1: Alignment Output.


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




fp=6.300 a

fp=1.390


=5.419 af=7.338 a

f=1.920

(10.4) a0 Check: a

0-a


(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: CTODDCG

-R = 1.41 da 0.82 (mm)



Figure A1.1: Base Metal A1.


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




fp=6.300 a

fp=1.390


=5.725 af=7.182 a

f=1.457

(10.4) a0 Check: a

0-a


(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: CTODDCG

-R = 1.64 da 0.67 (mm)



Figure A1.2: Base Metal E1.


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




fp=6.577 a

fp=1.528


=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: CTODDCG

-R = 1.82 da 0.53 (mm)



Figure A1.3: Base Metal H1.


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.


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




fp=6.965 a

fp=1.941


=5.563 af=7.164 a

f=1.601

(10.4) a0 Check: a

0-a


(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: CTODDCG

-R = 1.84 da 0.44 (mm)



Figure A1.5: Base Metal K1.


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


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


Figure A1.6: Base Metal K1 – Crack Lengths.


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




fp=7.246 a

fp=2.196


=5.085 af=6.864 a

f=1.779

(10.4) a0 Check: a

0-a


(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: CTODDCG

-R = 1.10 da 0.76 (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%





fp=7.246 a

fp=2.196


=5.085 af=6.864 a

f=1.779

(10.4) a0 Check: a

0-a


(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: CTODDCG

-R = 1.10 da 0.76 (mm)



Figure A2.1: All Weld Metal W2-A1.


0 2 4 6 8 10 12 145

5.5

6

6.5

7

7.5

8

mm

mm



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


Figure A2.2: All Weld Metal W2-A1 – Crack Lengths.


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%





fp=7.284 a

fp=2.272


=5.008 af=6.915 a

f=1.907

(10.4) a0 Check: a

0-a


(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: CTODDCG

-R = 1.28 da 0.64 (mm)





0 2 4 6 8 10 12 144.5

5

5.5

6

6.5

7

7.5

mm

mm



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




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%





fp=7.580 a

fp=2.566


=4.988 af=7.183 a

f=2.195

(10.4) a0 Check: a

0-a


(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: CTODDCG

-R = 1.18 da 0.63 (mm)





0 2 4 6 8 10 12 144.5

5

5.5

6

6.5

7

7.5

8

mm

mm



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




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%





fp=6.300 a

fp=1.240


=5.710 af=6.909 a

f=1.199

(10.4) a0 Check: a

0-a


(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: CTODDCG

-R = 1.09 da 0.76 (mm)





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%





fp=6.508 a

fp=1.503


=4.986 af=6.265 a

f=1.279

(10.4) a0 Check: a

0-a


(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: CTODDCG

-R = 1.83 da 0.54 (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%





fp=6.508 a

fp=1.503


=4.986 af=6.265 a

f=1.279

(10.4) a0 Check: a

0-a


(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: CTODDCG

-R = 1.83 da 0.54 (mm)



Figure A3.1: Notch Fusion Line W2-A2.


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



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


Figure A3.2: Notch Fusion Line W2-A2 – Crack Lengths.


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%





fp=6.743 a

fp=1.657


=4.968 af=6.584 a

f=1.616

(10.4) a0 Check: a

0-a


(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: CTODDCG

-R = 1.84 da 0.52 (mm)





0 2 4 6 8 10 12 144.5

5

5.5

6

6.5

7

7.5

mm

mm



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




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%





fp=6.810 a

fp=1.712


=5.006 af=6.659 a

f=1.654

(10.4) a0 Check: a

0-a


(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: CTODDCG

-R = 1.86 da 0.54 (mm)





0 2 4 6 8 10 12 144.5

5

5.5

6

6.5

7

7.5

mm

mm



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




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%





fp=7.063 a

fp=2.284


=5.004 af=6.579 a

f=1.575

(10.4) a0 Check: a

0-a


(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: CTODDCG

-R = 1.87 da 0.49 (mm)





0 2 4 6 8 10 12 144.5

5

5.5

6

6.5

7

7.5

mm

mm



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






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



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.

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DRDC – Atlantic Research Centre Defence Research and Development Canada 9 Grove Street P.O. Box 1012 Dartmouth, Nova Scotia B2Y 3Z7 Canada

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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

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e.g., interim, progress, summary, annual or final. Give the inclusive dates when a specific reporting period is covered.)

Scientific Report

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DRDC – Atlantic Research Centre Defence Research and Development Canada 9 Grove Street P.O. Box 1012 Dartmouth, Nova Scotia B2Y 3Z7 Canada

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10a. ORIGINATOR’S DOCUMENT NUMBER (The official document

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DRDC-RDDC-2015-R156

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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

Documents

Evaluation of the single edge notch tension specimen for ...cradpdf.drdc-rddc.gc.ca/PDFS/unc203/p802059_A1b.pdf · specimen for quantifying fracture toughness Participation in a round-robin