PSI - Issue 2_B

N.A. Alang et al. / Procedia Structural Integrity 2 (2016) 3177–3184 Author name / StructuralIntegrity Procedia 00 (2016) 000 – 000

3184

8

5. Conclusion

The influence of strain amplitude and strain rate on the LCF behaviour of P92 steel at 600°C was investigated. Based on the studies, the following conclusions have been drawn:

 Under the LCF test conditions, the ex-service P92 steel exhibited continuous cyclic softening and no saturation stage was observed. Rapid decrement in the cyclic stress response was shown at the initial stage before the material gradually softens until the micro-crack initiation point is reached.  The LCF life was significantly affected by both strain amplitude and strain rate. Therefore, the two factors must be considered when planning further tests. At constant strain amplitude, the relationship between the time to failure and strain rate can be expressed mathematically by the power law relation.  At higher strain rates, the crack propagated intergranularly which due to fatigue while at lower strain rates the crack may be propagated in both inter- and transgranular manner. The deformation of grain boundaries sliding are more prevalent at the lower strain rates and longer dwells therefore, the reduction of material lifetime could be due to an increasing of creep cracking. ASTM E606., 2012. Standard Test Methods for Strain-Controlled Fatigue Testing. ASTM International. Biglari, F., Lombardi, P., Budano, S., Davies, C.M., Nikbin, K.M., 2012. Predicting Damage and Failure under Low Cycle Fatigue in a 9Cr Steel. Fatigue and Fracture of Engineering Material and Structures 35, 1079-1087. Giroux, P.F., 2011. Experimental Study and Simulation of Cyclic Softening of Tempered Martensite-Ferritic Steels. PhD Thesis, MINES ParisTech., France. Haddar, N., Köster, A., Remy, L., 2012. Thermal – Mechanical and Isothermal Fatigue of 304L Stainless Steel under Middle Range Temperatures. Comptes Rendus Mécanique 340, 444 – 52. Hong, S.G., Lee, S.B., 2004. The Tensile and Low Cycle Fatigue Behaviour of Cold Worked 316L Stainless Steel: Influence of dynamics strain aging. Int. J. of Fatigue 26, 899-910. Hormozi, M.R., Biglari, F., Nikbin, K.M., 2013.Investigation of Stress Stabilization Behaviour of Type 316 Steel. Proceeding of the ASME Pressure Vessels and Piping, Paris, France, PVP2013-97593. Huang, Z.W., Wang, Z.G., Zhu. S.J., Yuan. F.H., Wang, F.G., 2006.Thermomechanical Fatigue Behaviour and Life Prediction of a Cast Nickel Based Superalloy. Material Science Eng. A 432, 308 – 16. Kannan, R., Vani, S.R., Mathew, M.D., 2013. Comparative Evaluation of the Low Cycle Fatigue Behaviours of P91 and P92 Steels. Procedia Engineering 55, 149-153. Lee, D., Shin, I., Kim, Y., Koo, J.M., Seok, C.S., 2014. A Study on Thermo-Mechanical Fatigue Life Prediction of Ni-Base Superalloy. Int J Fatigue 62, 62 – 6. Luo, Y.R., Huang, C.X., Tian, R.H., Wang, Q.Y., 2013.Effect of Strain Rate on Low Cycle Fatigue Behaviours of High-Strength Structural Steel. Journal of Iron and Steel Research 20:7, 50-56. Mishnev, R., Dudova, N., Kaibyshev, R., 2015. Low Cycle Fatigue Behaviour of a 10% Cr Martensitic Steel at 600°C.ISIJ International 55:11 2469-2476. Richa, A., Rashmi, U., Pramod, P., 2014. Low Cycle Fatigue Life Prediction. Int. J. Emerging Engineering Research and Technology 2:4, 5-15. Wang, X., Gong, J., Jiang, Y., Zhao, Y., 2015. Low Cycle Fatigue Behaviour of Original Ferritic P92 Steel at High Temperature: Experiments and Simulations. Proceeding of the ASME Pressure Vessels and Piping, Boston, USA, PVP2015-45353. Zhang, Z., Hu, Z.F., Fan. L.K., Wang, B., 2015. Low Cycle Fatigue Behaviour and Cyclic Softening of P92 Ferritic-Martensitic Steel. J. of Iron and Steel Research 22:6, 534-542. References