Interpretation of small ring creep test data

The small ring creep test method can be used to generate uniaxial secondary creep strain rate data from small samples of material. The technique used is based on the reference stress method; it enables the load-line displacement rates, obtained from testing the rings, to be converted to equivalent uniaxial creep strain rates. Accurate conversion relationships are required, in order to ensure that accurate creep properties are obtained. In this article, an analysis of the creep behaviour of small, ring-type specimens and the associated test procedures are described. This includes the determination of the conversion factors, which are used to convert the minimum creep displacement rate to the equivalent uniaxial minimum creep strain rate and to convert the nominal stress to the equivalent uniaxial stress, using the finite element method. In addition, an assessment of the effects of ring dimensions, for example, the radial thickness and mean radius, on the conversion factors, is made. Finally, the effects of...