13th International Conference on Fracture June 16–21, 2013, Beijing, China who assumes that the critical distance is dependent on the number of cycles to failure, which is successfully applied to LCF issues. The relationship between critical distance DPM(Nf) and failure life Nf is shown in Eq. 5，the fitted curve is shown in Fig. 20 and Fig. 21 shows a factor of two in life prediction. 0.08153 ( ) 0.31133 PM f f D N N （5） 100 1000 10000 100000 0.01 0.1 1 850 o C, DZ125,L U-type notched plate O-type notched plate Crtical distance(mm) Cycles to Failure (Cycles) Fig. 20 The experimental critical distances for each test specimen 100 1000 10000 100000 1000000 100 1000 10000 100000 1000000 DZ125,850 o C,L O-type notched plates U-type notched plates Predicted fatigue life(Cycles) Experimental fatigue life(Cycles) Fig. 21 Experimental life with stress concentration versus predicted life 4.2.3 Life prediction under both stress concentration and dwells Based on SWTM parameter, Miner’s linear cumulative damage theory and Larson-Miller plots, acceptable life prediction on LCF with dwell times could be gotten. However, to predict LCF life affected by both stress concentration and dwell times, firstly the fatigue damage is calculated based on the critical distance concept in obtained Eq. 5, then the concentrated stress should be average processed for determining creep damage; the equivalent stress is confirmed by the tensile strain weighted correction shown in Eq. 6, where the integration interval is on the middle line of notched plate. As is shown in Table 2, this method shows acceptable accuracy for LCF life affected by both dwell times and stress concentration. , 33 33 33 / creep eq d d （6） Table 2 Experimental life with concentrated stress and dwells at 850℃ versus predicted life ∆σnet/ MPa Predicted DPM/mm Predicted pure fatigue life/Cycles Equivalent stress/MPa Predicted creep life/hour Hold time/s Predicted life/Cycles Experimental life/Cycles 25-321 0.1235 83964.85 560.825 46.6051 120 1375.3 1150 25-375 0.1348 28696.96 636.728 14.5199 120 429.1 609 25-412 0.1431 13822.23 689.174 6.8279 120 201.8 355 5 Conclusion Based on the author and co-worker’s systemically experimental investigation work on smooth and notch fatigue behavior of DZ125 at high temperatures with and without dwell times, LCF behavior analysis and life modeling considering the influence of temperature, dwells and stress concentration is carried out. The main conclusions are summarized as follows: (1) The influence of temperature, strain ratio, stress concentration, dwell types and
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