The ECCC Approach to Creep Data Assessment

The ECCC (European Creep Collaborative Committee) approach to creep data assessment has now been established for almost 10 years. The methodology covers the analysis of rupture strength and ductility, creep strain and stress relaxation data, for a range of material conditions. This paper reviews the concepts and procedures involved. The original approach was devised to determine Data Sheets for use by committees responsible for the preparation of National and International Design and Product Standards, and the methods developed for data quality evaluation and data analysis were therefore intentionally rigorous. The focus was clearly on the determination of long time property values from the largest possible datasets involving a significant number of observations in the mechanism regime for which predictions were required. More recently, the emphasis has changed. There is now an increasing requirement for full property descriptions from very short times to very long, and hence the need for much more flexible model representations than were previously required. There continues to be a requirement for reliable long time predictions from relatively small datasets comprising relatively short duration tests, in particular to exploit new alloy developments at the earliest practical opportunity. In such circumstances, it is not feasible to apply the same degree of rigour adopted for large dataset assessment. Current developments are reviewed.