The reliability of S shaped curve creep models when the high temperature tensile strength is strain rate dependent

It is important to be able to predict the creep life of materials used in power plants and aeroengines. This paper illustrates the role played by a materials tensile strength in achieving this. It also shows that published high temperature tensile strength values are not always suitable for use in certain creep models due to its strain rate dependency. Using strain rates larger than those used by NIMS (0.00125/s) resulted in more sensible estimates of the activation energy for creep. Using these larger strain rates also resulted in an improved fit of these models to the experimental data. Using a strain rate of 0.0133/s instead of 0.00125/s also lead to substantial reduction in the proportion of any prediction error that was random in nature. When using a strain rate of 0.0133/s, good predictions of life out to 130,000 h can be made from data with a maximum life of 1230 h. • Importance of strain rate in use of S shaped curve creep models to estimate activation energy for creep. • Importance of strain rate in use of S shaped curve creep models to represent creep properties. • Importance of strain rate in use of S shaped curve creep models to obtain reliable creep life predictions. • Importance of strain rate in use of S shaped curve creep models to obtain random creep life prediction errors.