Experience in Applying the New UK Procedure for Creep Rupture Data Assessment to Gas Turbine Materials

A new procedure being developed in British Standards for the assessment of creep-rupture data is described, and evaluated with trial data sets of gas turbine blading materials. The procedure is applied in phases. An important development by statistical experts is a framework for the main assessment phase which uses maximum-likelihood fitting methods for the treatment of unfailed test points and error variance. The framework selects models from a standard suite (together with any other linear models supplied by the assessor) using statistical criteria, but also incorporates metallurgical judgement. The improved representation of the experimental data compared with previous fitting methods, and the associated statistical tests indicate that the new procedure can be used to derive rupture strength values for gas turbine materials with confidence.