Applicability of Modified Diercks Equation with NRIM Data

The applicability of the modified Diercks equation (MDE) was assessed with elevated temperature low cycle fatigue (ETLCF) data generated by the National Research Institute for Metals (NRIM) for lCr-Mo-V, 1.25Cr-Mo, 2.25Cr-Mo and 9Cr-lMo steels respectively. The modified Diercks equation was assessed with data generated with symmetrical, slow-fast and hold-time waveforms for low alloy steels. The following characteristics were observed: Symmetrical waveforms: Five strain rates were used with these waveforms where predicted life was by a factor of ± x2 for 77%, 87%, 82% and 92% of data points for lCr-Mo-V, 1.25Cr-Mo, 2.25Cr-Mo and 9CrlMo steels respectively. Slow-fast waveforms: Diercks equation was not applicable when the test parameters in tension and compression changed. However, when assessed with such data, predicted life was by a factor of ± x2 for 93%, 66% and 66% of data for lCr-Mo-V, 2.25Cr-Mo and 9Cr-lMo steels respectively. Holdtime waveforms: Tensile only holds of 0.1 and 1 hour were applied where the predicted life was by a factor of ± x2 for 88%, 50% and 100% of test data for lCr-Mo-V, 2.25Cr-Mo and 9Cr-lMo steels respectively.