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Fracture toughness round robin on type 316L mod. steel in a thermally aged condition

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200 pages
Nuclear energy and safety
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ISSN 1018-5593
European Commission
nuclear science
and technology
Fracture toughness round robin on
type 316L mod. steel in a thermally
aged condition
Report
EUR 14998 EN Publication of this report has been supported by the Dissemination of Scientific and Technical
Knowledge Unit, Directorate-General for Telecommunications, Information Market and
Exploitation of Research, European Commission, Luxembourg European Commission
nuclear science
and technology
Fracture toughness round robin on
type 316L mod. steel in a thermally
aged condition
H. Huthmann,1 A. Cornee,2 E. Lucon,3 P. Nicolino,4 S. Ragazzoni,5
H. J. M. Van Rongen,6 G. Wardle7
'Siemens (Interatom) - Bergisch Gladbach, Germany
2GKSS - Geesthacht, Germany
3CISE - Milan, Italy
4CEA - Saclay, France
5ENEL-Milan, Italy
TNO - Apeldoorn, The Netherlands
7AEA - Risley, United Kingdom
Contract No RA1-0107 D
Final report
This work was performed under the Commission of the European Communities for the Working Group Codes and
Standards, Activity Group 3: 'Materials' within the Fast Reactor Coordinating Committee
Directorate-General ¿çffCyJVjJ2í
Science, Research and Development
1994 Published by the
EUROPEAN COMMISSION
Directorate-General XIII
Telecommunications, Information Market and Exploitation of Research
L-2920 Luxembourg
LEGAL NOTICE
Neither the European Commission nor any person acting on
behalf of the Commission is responsible for the use which might be made of the
followina information
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1994
ISBN 92-826-7444-4
© ECSC-EC-EAEC, Brussels • Luxembourg, 1994
Printed in Belgium FOREWORD AND EXECUTIVE SUMMARY
The Commission of the European Communities is assisted in its actions regarding fast
breeder reactors by the Fast Reactor Coordinating Committee which has set up the
Safety Working Group and the Working Group Codes and Standards (WGCS). The
latter's mandate is to harmonize the codes, standards and regulations used in the EC
member countries for the design, material selection, fabrication and inspection of
LMFBR components.
The present report is the revised final report of CEC Study Contract RA1-0107-D
performed under WGCS/Activity Group 3: "Materials". As for all other study contracts
in this area, Activity Group 3 (AG3) monitored the progress of the work and discussed
the draft final report. Furthermore, the final report was reviewed before its publication
as an EUR.
Fracture toughness tests (J-Aa and CTOD-Aa) have been performed within an
experimental round robin on thermally aged 316L Mod. steel,[agreed designation for
the European Fast Reactor: 316L(N)] with a thermal ageing corresponding to end of
life conditions. Even after this ageing this steel is in a condition of high toughness with
large plastic deformations upon loading.
The applicability of the EGF recommendation for the determination of R-curves has
been checked and comparisons with ASTM E813 and further national standards have
been drawn. In conclusion, the EGF method can generally be applied, if some
modifications due to the high plastic deformations are taken into account and the
validity limits are extended for plane stress conditions.
It has been demonstrated that single specimen techniques [potential drop (PD) and
unloading compliance (ULC)] can be applied successfully providing that due
consideration is given to the large plastic deformations and displacements, e.g.
calibration of crack extension as a function of potential drop for PD-technique and
experimental checks of the large rotation correction for ULC-method are necessary.
Agreed J-Aa and CTOD-Aa curves have been found for CT- and SENB3-specimens
with about 20 mm net thickness and 50 mm width. Additional tests on specimens with
100 mm width show somewhat higher R-curves, which may be due to the different
constraint given by the ratio of thickness to ligament.
The measured R-curves are above the validity limits of the current procedures of EGF
and ASTM, which are confirmed by a reassessment of the HRR near field for austenitic
stainless steels. Not even crack initiation occurs under plane strain conditions required
for geometry-independent deformation J-integrals given by EGF and- ASTM.
The global deformation behaviour tends to quasi plane stress conditions. Side-grooving
does not promote plane strain conditions significantly and should not be applied in
future tests on austenitic stainless steels. The validity limits in dependence of the ligament size have been determined for plane
strain and plane stress conditions (Fig. 49). Additionally, the validity limits have been
assessed by an engineering approach, which increases the limit for deformation integrals
up to 1150 N/mm for specimens with 50 mm width with a crack extension limit of 6 %
of ligament.
Even higher validity limits seem to be acceptable for the J-integral, JM, modified by
Ernst and the CTOD parameters ¿æ-mod and S5, which is a directly measured
parameter. From this and because JM and Ss can be linearly correlated and they indicate
constant slopes dJ^da and dSjda after a transition range, JM and 6S are the most
promising parameters.
-IV Contents Page
Notation y-fj
1 Introduction 1
2 Objectives 2
3 Material 4
4 Test Conditions and Requirements 5
5 Evaluation Procedures 7
5.1 Estimation of J- and CTOD-Values
5.2 Crack Extension Measurements
5.3 Blunting Line 8
5.4 Critical Stretch Zone Width Measurement 9
5.5 Regression Curves for J and 8 10
6 Test Results 12
6.1 Results from Multi-Specimen Technique
6.1.1 Comparison with Validity Limits4
6.1.2 Fit of Regression Curves5
6.1.3 Critical Values of Crack Initiation 17
6.2 Single-Specimen Techniques 19
6.2.1 Unloading Compliance Technique
6.2.2 Potential Drop Technique 20
6.3 Influence of Specimen Width1
7 Promising Parameters JM and CTOD3
8 Reassessment of the Current Validity Limits 25
8.1 General Remark 2
8.2 Classical Validity Limitations 25
8.3 Thickness Criteria for Plane Strain7
8.4 Ligament Validity Limitation JD*
Including Crack Extension Aa
8.5 New Engineering Approaches8
-V-Page
8.6 Conclusions from Reassessment of Validity Limits 30
9 Transferability to Components 33
10s and Recommendations5
11 References 41
12 -Tables
13 Figures 59
Recommendations for Stretch Zone Width (SZW) Enclosure 1:
Measurements Using Scanning Electron
Microscopy (SEM) 11
The Applicability of Unloading Compliance Enclosure 2:
Testing to Austenitic Steels 117
Enclosure 3: A Recommended Procedure for the Unloading
Compliance Testing of Austenitic Metals 135
Enclosure 4: Review of the Potential Drop Method 157
Appendix A: Reassessment of the Current Available
Validity Limits for Austenitic
Stainless Steels and the Meaning of J-
Aa Curves above these Limits
Technical Note GKSS WW/90/2
Appendices B to G: Original Reports of the performed
fracture toughness test by
B: CEA, Saclay, F
C: ENEL/CISE, Milano, I
D: GKSS, Geesthacht, FRG
E: Interatom, Bergisch Gladbach, FRG
F: TNO, Apeldoorn, N
G: UKAEA, Risley, UK
Remark: Appendices A to G are given in supplementary volumes.
-VI Notation
General Abbreviations
ASS Austenitic Stainless Steel
BL Blunting line
CTOD Crack-tip opening displacement
CT Compact tension (specimen)
DVM Deutscher Verband für Materialforschung und
-prüfung e. V.
EGF European Group on Fracture
FE Finite element
HRR Asymptotic crack-tip field after Hutchingson, Rice &
Rosengren
SENB3 Three-point bend (specimen)
SZW Stretch zone width
Dimensions
a Crack length
a0 Initial crack length
B Specimen thickness
Bn Net thickness of sidegrooved specimens
S Span of single edge notch bend specimen
W Specimen width
z Knife edge height
Material Properties
Young's modulus E
Poisson's ratio v
Yield strength equivalent to 0.2 percent proof stress °y
Ultimate tensile stress
Ou
Flow stress (oy + au)/2
Of
Loads and Deformations
P Load
Py Yield load, calculated using oy
PL Ultimate load,d using au
R Ratio of lower to upper load during fatigue cracking
A Load point displacement
U Energy under load vs. load point displacement trace
Vg Mouth openingt
Vp Plastic component of the mouth opening displacement
VII Fracture Parameters and Related Quantities
Aa Average crack growth
AaSZw Critical stretch zone width
Aamax Validity limit for J-controlled crack growth
Aag Limit of J-controlled crack growth
Aai Reduced limit ford crack growth
j0 Fracture resistance not allowing for crack growth
J, Jcorree allowing for crack growth
Je Elastic J (ASTM)
Jp Plastic J)
Ji Fracture resistance at crack initiation
J0.2/BLee at 0.2 mm crack growth beyond
initiation
Jo.2e resistance at 0.2 mm crack growth
including blunting
JQ ASTM definition of Ji
dJ/da Slope of the J-Aa curve
Jg Fracture resistance at upper limit of J-controlled
crack growth
Jmax Validity limit for J
Q A non-dimensional quantity for characterizing
J-controlled crack growth
q(a/W) J-calibration function
80 Crack top opening displacement (CTOD) not allowing
for crack growth
8,8corr CTOD allowing for crack growth
8e Elastic 8
8p Plastici 8
8i CTOD at crack initiation
80.2/BLD at 0.2 mm crack growth beyond initiation
80.2D at 0.2 mmkh including blunting
d8/da Slope of the 8-Aa curve
8g CTOD at upper limit of 8-controlled crack growth
8max Validity limit for CTOD
K Stress intensity factor
AK Range of stress intensity factor in fatigue
F(a/W) Stress intensity function
VIII-