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Nuclear energy and safety

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• Publié par: EUROPEAN-UNION
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• Langue: English
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Commission of the European Communities
nuclear science and technology
STATE OF THE ART REPORT
ON FRACTURE MECHANICS
(FRACTURE IN THE CREEP RANGE)
Volume 1 : Report
Report
EUR 11728/1 EN
Blow-up from microfiche original Commission of the European Communities
nuclear science and technology
STATE OF THE ART REPORT
ON FRACTURE MECHANICS
(FRACTURE IN THE CREEP RANGE)
Volume 1 : Report
E.G. ELLISON, Coordinator (UK)
G.G. MUSICCO (Italy)
A. PINEAU (France)
Contract RAP 053 UK
FINAL REPORT
This work was performed
under the Commission of the European Communities
Study Contract
For the Working Group Codes and Standards
For the Activity Group 2 "Structural Analysis"
Within the Fast Reactor Coordinating Committee
PARI r •
Directorate-General Science, Research and Developme t|\| Q
i
1988 ¿EUR 11728 EN/
¿EUR 11" Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Telecommunications, Information Industries and Innovation
L-2920
LUXEMBOURG
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting on behalf
of then is responsible for the use which might be made of the following
information
Volume 1: Report
Volume 2: Appendices A-G e 3:s H-M
© ECSC—EEC—EAEC Brussels - Luxembourg, 1988 Ili
FOREWORD
A CEC State of the Art Report on Fracture Mechanics for Fast
Breeder Reactors (Fracture below the Creep Range) has recently been
published by Bhandarl and coworkers (1984). There has also been a
compilation of Creep Crack Growth Data from Germany, France and the
U.K. for 304 and 316 stainless steel by Lloyd et al (1984).
The present Report provides considerably more data and
analytical techniques taken from Worldwide sources on creep crack
initiation and propagation. Since the subject is moving quickly
there is an emphasis on the most recent work; indeed research
studies as yet unpublished are also included. The total Report is in
3 volumes. The main body of the report is contained in Volume 1;
this includes recommendations for the designer and for future work.
Volumes 2 and 3 contains the most important and up-to-date information
in some detail in Appendices A to M; this provides a sound base for
the Report and for future workers.
I would wish to thank my two collaborators Drs Musicco and
Pineau for their help in discussing, debating and critically assessing
the various data and techniques.
(PROFESSOR E G ELLISON)
1st October 1985 CONTENTS
Chapter
1 Introduction
1
1.1 Background
2
1.2 The Report
CEC Joint Exercise; Phases I and II
4
2.1 Summary
6
2.2 Preliminary Comments on Lloyd Phase II report
8
2.3 Concludings
12
Creep Fracture Mechanics
* 12
3.1 Creep Crack Parameter J 14
3.2p Regimes and Transition Times
3.3 Transition J* 2
3.4 Preliminary Experimental Data; Transition Times 25
Creep Crack Growth for Stainless Steels - Recent results 27
4.1 Static Creep Case7
4.2 Cyclic Creep Case 35
Critical Assessment of Experimental Data 42 46
4
5.1 The a vs J*Plot 448
5.2 Laboratory Crack Growth Rates
5.3 The Effect of Geometry
5.4 Temperature8
5.5 Concluding Comments
* 51
Use of the J Parameter
65
6.1 Transient J * 63
6.2 Analytical Calculation of J 63 6
Creep Crack Initiation
6.3 Concluding Comments
6
7.1 Introduction
69
7.2 Creep Crack Initiation from Notches
7.2.1 Stress - Strain Distribution9
70
7.2.2 Crackn
72
7.3 Creep Crack Initiation from Precracks
7
7.4 Concluding Remarks VI
Chapter
8 General Discussion
80
8.1 Influence of Creep and/or Environment 80
8.2 Remaining Life Prediction 81
8.2.1 Parameter J*
8.2.2 Local Approach3
8.2.3 Empirical Approaches5
(a) Frequency Factors 8
(b) Parametric Approach7
8.3 Constraint 8
8.4 Defining Dominant Regimes 89
8.5 Final Failure 92
9 Recommendations for the Designer 94
9.1 Creep Crack Initiation
9.2pk Propagation 95
9.2.1 Correlating Parameters
9.2.2 Which Correlating Parameter? 97
9.3 Final Failure 97
10 Recommendations for Future Work 99
11 Report Bibliography 102 CHAPTER 1
INTRODUCTION
1.1, Background
In modern power plant operating at elevated temperature,
components can be working under conditions when creep, fatigue and
environmental processes are present. In this report the l effect is not dealt with in any detail; the object has
been mainly to define how the combined effects of creep and fatigue
can affect crack propagation though some attention has also been given
to crack initiation.
The combined effects of creep and fatigue usually arise from
thermal transients and this entails advanced methods of analysis so
that a reliable assessment of the performance of the component or
structure can be made. The present ASME Code Case N-47 attempts to
deal with creep-fatigue essentially by predicting life to "crack
initiation" based on some definition of failure observed in laboratory
tests. The combination of creep and fatigue damage is estimated by a
simple linear summation. This approach for nominally unnotched and
undefected materials is of doubtful merit but again it must be stated
that this topic is not considered in this report. Suffice to say
that, in the opinion of the writers, a more promising route would be
based on ductility exhaustion; indeed this could well then be merged
into future crack analyses. However the major problem which concerns
us here is that the current design codes [ASME CC N-47 or BS 5500
1982] do not make any recommendations with regard to crack growth in
the creep regime. In addition to being able to predict the time required to
initiate a crack, it is essential that predictions of subsequent crack
growth be available. This would enable the remaining life of
components to be estimated when inspection during service operation
reveals defects. An appreciation of this aspect should also help
designers of advanced structures to take into account the possibility
of manufacture defects, as well as other cracks which may develop
during service, at the design stage. Then, of course, failure either
by fast catastrophic break or ductile collapse oust be assessed to
decide final failure; this final stage might be carried out by a
method analogous to the CEGB R.6 failure assessment route. In fact
in some circumstances, for example a very creep ductile material in a
plane stress state situation, it is possible that even in cracked
materials the life may be predicted by reference stress techniques
since the cracks are effectively blunted.
1.2. The Report
Since the subject of crack propagation in the creep regime
is moving at a rapid pace, this Report is in the main based on work
carried out in the last four years. Indeed there is some data and
analysis included which has not yet been published. All this
information has been reviewed in detail, and the more important parts
summarised and written into the Appendices A-fl As agreed at the
outset, information on materials not directly used in Fast Reactor
application are considered where it helps to provide a better under­
standing of this complex problem. The Appendices contain sections on
creep-fatigue, notched creep behaviour, damage mechanics, creep
fracture mechanics, as well as sections summarising the latest