PD 6605-1:1998

Foreword
Introduction
1 Scope
2 Normative references
3 Symbols and abbreviations
4 Overview
5 Initiation phase
6 Preassessment
7 Main assessment
8 Post-assessment
9 Reporting
Annex A (normative) Dataset size
Annex B (informative) Statistical principles and technical
details of proposed models
Annex C (informative) Worked example
Annex D (informative) Summary report of assessment results
Bibliography
Figure 1 Flow diagram for assessment of stress rupture data
Figure 2 Flow diagram of the main assessment
Figure B.1 Steps in the statistical modelling procedure
Figure B.2 Soviet model isothermal trend lines including
            and excluding unfailed tests
Figure C.1 Isothermal plots of broken and unbroken test
            data for 12Cr alloy steel
Figure C.2 Isothermal plots of best-tested casts for
            12Cr alloy steel
Figure C.3 Credibility of model fit
Figure C.4 Results of model fit
Figure C.5 Effectiveness of within-data-range model fit
            (all data), PAT-2.1, MH03
Figure C.6 Effectiveness of within-data-range model fit
            (all data), PAT-2.2, MH03
Figure C.7 Identification of influential casts
Figure C.8 Isothermal plots of broken and unbroken test
            data with MH03 model strength predictions
Figure D.1 Strength values versus temperature
Table 1 Symbols and abbreviations
Table 2 Stress-rupture data assessment procedure
Table 3 Acceptability criteria for robustness in
            extrapolation discrepancies exceeding u% of tr*
Table 4 Deviance criteria for subdivision of datasets
Table A.1 Recommended interim-minimum and target-minimum
            dataset sizes for provision of creep rupture
            strength values for standards (broken points)
Table B.1 Creep rupture models included in the
            recommended procedure
Table B.2 Statistical models used in the recommended
            procedure
Table B.3 Simulation results
Table B.4 Culling statistic corresponding to 50% of
            extrapolation discrepancies exceeding u % of tr*
Table C.1 Material specification for a 12Cr alloy steel
            dataset
Table C.2 Identification of possible duplicate test data
Table C.3 Details of tested materials
Table C.4 Quantity and duration of data used in the
            assessment
Table C.5 Quantity and duration of unique materials used
            in the assessment
Table C.6 Identification of best-tested casts
Table C.7 Results of model fitting
Table C.8 Initial and final model selection
Table C.9 Preferred model selection
Table C.10 Predicted strength values for MH03
Table C.11 Results of ECCC PAT-3 time cull for MH03
Table D.1 Summary report of assessment results (12Cr
            alloy steel)
Table D.2 Quantity and duration of data used in the
            assessment
Table D.3 Predicted rupture strengths

Gives guidance in assessing multi-source, multi-cast, multi-temperature stress rupture date for determining reliable strength values for durations within and beyond the data range. Mainly intended for deriving the creep rupture strength values for including in standards, and ultimately for formation of the basis of design strength values in relevant specifications and codes. The methodology applies equally to provision of rupture strength values for other purposes, in addition to a wider spectrum of ferrous and non-ferrous materials.