1、 Reference number ISO/TTA 5:2007(E) ISO 2007TECHNOLOGY TRENDS ASSESSMENT ISO/TTA 5 Second edition 2007-10-15Code of practice for creep/fatigue testing of cracked components Code de bonne pratique pour les essais de fluage/fatigue des composants fissurs ISO/TTA 5:2007(E) PDF disclaimer This PDF file
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6、ntry of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2007 All rights reservedISO/TTA 5:2007(E) ISO 2007 All rights reserved iii Foreword ISO (the Internationa
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13、n information that would normally form the basis of standardization. ISO has decided to publish such documents to promote the harmonization of the objectives of ongoing prestandardization work with those of new initiatives in the Research and Development environment. It is intended that these public
14、ations will contribute towards rationalization of technological choice prior to market entry. Whilst ISO/TTAs are not Standards, it is intended that they will be able to be used as a basis for standards development in the future by the various existing standards agencies. Attention is drawn to the p
15、ossibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO/TTA 5 was prepared by VAMAS TWA25 and published under a memorandum of understanding concluded between ISO and VAMAS. This se
16、cond edition cancels and replaces the first edition (ISO/TTA 5:2006), which has been technically revised. ISO/TTA 5:2007(E) iv ISO 2007 All rights reservedContents Page 1 EXECUTIVE SUMMARY 1 2 SCOPE 1 3 SPECIFIC OBJECTIVES 2 4 INTRODUCTION. 2 4.1 Background to VAMAS Creep Crack Growth Initiatives .
17、3 4.2 Background to Industrial needs for validated Test Data 3 4.3 Relevance of Testing Methods to Life Assessment Codes 4 4.3.1 Background to Life Assessment Codes .4 4.3.2 Relation between laboratory tests and Component Assessment Codes . 5 4.3.3 Factors involved in the development of assessment c
18、odes 5 4.4 Requirements for the VAMAS TWA 25 CoP . 6 4.5 ISO requirements 6 4.5.1 ISO Technology Trend Assessment (ISO/TTA) 7 5 Acknowledgements 7 5.1 List of participants in VAMAS TWS25. 7 6 NOMENCLATURE AND ABBREVIATIONS 8 6.1 Nomenclatures 8 6.2 Listing of abbreviations 9 7 DESCRIPTION OF CREEP A
19、ND FATIGUE CRACKING 10 7.1 Failure due Creep Crack Growth (CCG)10 7.2 Creep Crack Initiation (CCI) . 10 7.3 Transient crack growth conditions . 10 7.4 Steady state Creep Cracking (CCG) 10 7.5 Fatigue and Creep/Fatigue Crack Growth (FCG and CFCG) 11 7.5.1 Failure due to fatigue 11 7.5.2 Creep/Fatigue
20、 interaction. 11 7.6 Factors affecting CCI, CCG and CFCG .11 7.6.1 Creep properties . 11 7.6.2 Metallurgical effects 12 7.6.3 Presence of residual stress fields. 12 7.6.4 Aggressive environments 12 7.6.5 Anisotropic and inhomogeneous material characteristics 12 8 TEST METHODS 13 8.1 Overview 13 8.2
21、Test Geometries 13 8.3 Experimental Test Methods . 14 8.3.1 Material procurement 14 8.3.2 Specimen selection. 14 8.3.3 Crack-plane orientation 14 8.3.4 Specimen machining . 14 8.3.5 Specific size requirements. 15 8.3.6 Specific side-grooving requirements 15 8.3.7 Shape of the crack front . 15 8.3.8
22、Pre-cracking to introduce a sharp flat crack front . 15 8.3.9 Pre-cracking for CCI tests 15 8.3.10 Crack length measurements 16 8.3.11 The use of Potential Drop (PD) 16 8.3.12 Preparing the specimens for PD leads . 16 8.3.13 Specimen setup. 16 ISO/TTA 5:2007(E) ISO 2007 All rights reserved v 8.3.14
23、Loading and creep displacement measurements 16 8.3.15 Displacement gauge17 8.3.16 Heating of the specimens .17 8.3.17 Initial pre-load 17 8.3.18 Monitoring the temperature 17 8.3.19 Unplanned temperature excursions 17 8.3.20 Initial pre-load 18 8.3.21 Specimen loading 18 8.4 Data Collection.18 8.4.1
24、 Detailed test and data monitoring18 8.4.2 Data logging .18 8.4.3 Displacement measurements.18 8.5 Post-Test Measurements 19 8.5.1 Measurement of the final crack front.19 8.5.2 Crack tip bowing19 8.5.3 Crack extension criteria 19 8.5.4 Crack deviation criteria .19 8.6 Recommended Minimum Number and
25、Duration for Tests20 8.6.1 Batch to batch variability 20 8.6.2 Minimum test requirements20 8.6.3 Single point data per test21 8.6.4 Multiple points data per test 21 8.6.5 Test duration requirements 21 8.7 Sensitivity and Accuracy Limits of the Results21 8.7.1 Effects of data variability on correlati
26、on for FCG, CCG and CCI21 8.8 Preparation of Test Data .22 8.8.1 Data collection .22 8.8.2 Time at which the test should be stopped 22 8.8.3 Smoothing the PD output data.22 8.8.4 Deriving the crack length from the PD output 22 8.8.5 Recommended number of data points 23 8.8.6 Calculating cracking and
27、 displacement rates 23 9 DATA ANALYSIS PROCEDURES .23 9.1 Choosing an appropriate CCI or CCG rate Correlating Parameter.23 9.1.1 Choice of parameter for correlating CCG .23 9.1.2 Choice of the C* term for CCG rate23 9.1.3 Choice of parameter for CCI .24 9.2 Definitions for the relevant Fracture Mech
28、anics Parameters .24 9.2.1 Stress intensity factor, K 24 9.2.2 J-integral.24 9.2.3 The C* parameter .24 9.2.4 Creep zone25 9.2.5 Steady state creep .25 9.2.6 The C tparameter26 9.2.7 Small-scale creep.26 9.2.8 Interpretation of C* parameter26 9.2.9 Time Dependant Failure Assessment Diagram (TDFAD) f
29、or CCI .26 9.2.10 The Q* Parameter.27 9.3 Criteria for Validity Checks of C* and K 27 9.3.1 Check for validity of C* .27 9.3.2 Components of displacement rates.27 9.3.3 Validity criteria for C* for highly ductile materials .28 9.3.4 Validity criteria for creep brittle materials.29 9.3.5 Transition t
30、ime criteria for C* .29 10 REPORTING PROCEDURES .30 10.1 Details of test information to be reported .30 10.1.1 Report of findings30 10.1.2 Pedigree of the material 30 10.1.3 Material properties to be logged 30 ISO/TTA 5:2007(E) vi ISO 2007 All rights reserved10.1.4 Test machine description. 30 10.1.
31、5 Details of starter crack . 30 10.1.6 Details for loading. 30 10.1.7 Report of data analysis. 30 10.1.8 Plots of data. 31 10.1.9 Tabulation of results. 31 10.1.10 Photographic/micrographic evidence. 31 10.1.11 Treatment of anomalous data 31 11 CORRELATING CRACK GROWTH USING FRACTURE MECHANICS 31 11
32、.1 CCG rate analysis . 31 11.2 Crack Initiation (CCI) Analysis. 32 11.3 FCG rate Analysis 32 11.4 Creep/fatigue crack growth rate analysis. 33 12 Methods for Calculating the C* Parameter . 33 12.1 Experimental Estimates of C* 33 12.2 Reference Stress Method of Estimating C* 34 13 APPENDIX I 36 13.1
33、Test Specimen Geometries 36 13.2 Geometry Definitions for Laboratory Specimens 36 14 SPECIMEN FRACTURE MECHANICS PARAMETER SOLUTIONS 38 14.1 Stress Intensity Factor K 38 14.2 Solutions for the Y function. 38 14.2.1 Y factor for C(T) 39 14.2.2 Y factor for CS(T) 39 14.2.3 Y factor for for SEN(T) . 39
34、 14.2.4 Y factor for SEN(B) (3 Point Bend Specimen). 39 14.2.5 Y factor for DEN(T). 40 14.2.6 Y factor for M(T) . 40 14.3 C* Solutions. 40 14.4 Reference Stress ( ref ) Solutions. 41 14.4.1 ref for C(T). 41 14.4.2 ref for CS(T) 42 14.4.3 reffor SEN(T) 42 14.4.4 ref for SEN(B) (3 Point Bend Specimen)
35、. 42 14.4.5 ref for DEN(T) 42 14.4.6 ref for M(T) 43 14.5 Functions for cracked geometries . 43 14.5.1 Nomenclature (see Figure A.1.3) . 43 14.5.2 Solutions for creep crack growth parameter, C* . 44 14.5.3 Best fit solutions of from finite element calculations . 45 14.5.4 Choice of for evaluating C*
36、 for material CCI and CCG properties 45 14.5.5 Choice of for evaluating C* in life assessment. 45 14.6 Function Equations . 46 14.6.1 functions for C(T). 46 14.6.2 functions for CS(T) . 46 14.6.3 functions for SEN(T). 46 14.6.4 functions for SEN(B) 3PB 47 14.6.5 functions for DEN(T). 47 14.6.6 funct
37、ions for M(T) . 47 14.7 Table for LLD . 49 14.8 Table for CMOD . 50 14.9 Geometry Definitions for Feature Type Specimens. 51 14.9.1 Details form Pipe, Plate and Notched bar feature specimens 51 14.10 Fracture Mechanics Functions for Feature Components . 52 14.10.1 K solutions for pipes and plates 52
38、 14.10.2 Reference stress solutions for pipes 53 14.10.3 Reference stress solutions for plates. 53 ISO/TTA 5:2007(E) ISO 2007 All rights reserved vii 14.10.4 Stress intensity factor K for the round notch bar 54 14.10.5 C* parameter for the notched bar.54 15 APPENDIX II :(TDFAD) c mat K approach for
39、CCI.55 15.1 Introduction55 15.2 Nomenclature.55 15.3 Failure Assessment Diagram .56 15.4 Materials Data Requirements .57 16 APPENDIX III: The Q* Parameter61 16.1 Symbols and Designations.61 16.2 Scope 62 16.3 Specimen Geometry 62 16.4 Guideline for Calculation of the Q* parameter62 16.4.1 Crack Grow
40、th Analysis .62 16.4.2 Crack initiation Analysis .63 17 APPENDIX IV: Local CTOD Approach .64 17.1 Crack Tip Opening Displacement (CTOD).64 18 APPENDIX V: Further Detailed Advice on Testing66 18.1 Advice on Testing and Machine Specification .66 18.2 Loading Machine66 18.3 Machine Tolerances 66 18.4 G
41、rips66 18.5 Alignment .66 18.6 Specimen Dimensional Measurement .67 18.7 Specimen Preparation.67 18.8 Permissible Temperature Deviation.67 18.9 Temperature Hold-time before start of Test67 18.10 Thermocouple Junction and Wiring 67 18.11 Thermocouple Attachment .68 18.12 Verification of Thermocouple.
42、68 18.13 Application of Load .68 18.14 Loading Precautions .68 18.15 Displacement Measurement .68 18.16 Apparatus for Crack Size Measurement69 18.17 Potential Difference (PD) Performance .69 18.18 Specimen Preparation for Electric Potential Measurement 69 18.19 Premature Test Failure69 18.20 Recomme
43、nded Method for Treating Extensive Plasticity .69 18.21 Recommended Data Reduction Techniques 70 18.21.1 Calculating the cracking and displacement rates70 18.21.2 Method for calculating the cracking and displacement rates.70 18.21.3 Secant method for deriving CCG and displacement rates70 18.21.4 Inc
44、remental polynomial method to derive CCG and displacement rates 70 18.21.5 Calculating crack length .71 18.21.6 Voltage versus crack length relation.71 19 REFERENCES Related International Standards and Codes 72 20 REFERENCES Relevant Publications.74 TECHNOLOGY TRENDS ASSESSMENT ISO/TTA 5:2007(E) ISO
45、 2007 All rights reserved 1 Code of practice for creep/fatigue testing of cracked components 1 EXECUTIVE SUMMARY Following a brief description of the mechanism for creep and creep/fatigue this document details testing methods and analysis procedures needed for creep and creep/fatigue crack growth te
46、sting of generic geometries containing cracks. Use of the terms generic geometries, component or feature component, feature specimens in testing assumes that the test geometry is non-standard as compared to standard laboratory fracture mechanics geometry such as the Compact Tension (C(T). These test
47、s maybe needed when the users need additional validation of results and in cases where excessive costs, unavailability of pedigree material, and other testing constraints would allow nominal numbers of tests can be carried out. So far as available, specific advice and additional reference material i
48、s given throughout the document in order to assist the user in carrying out a programme of testing and analysis of the data. Specific geometries are identified and appropriate fracture mechanics parameters are presented for each of them. This document takes into account the experience gained in test
49、ing techniques from previous Standards and Codes of Practice a-kk and integrates early advances in the field of high temperature fracture mechanics 1-23 with the more recent findings 24-80 to give advice on testing, measurement and analysis of CCI, CCG and CFCG data for a range of creep brittle to creep ductile materials using a very wide range of pre-cracked geometries. In quantitative terms the information from these tests can be used to consider the individual and combined effects of
