PSI - Issue 7

L.L. Liu et al. / Procedia Structural Integrity 7 (2017) 174–181

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L. L. Liu et al. / Structural Integrity Procedia 00 (2017) 000–000

strengthening theory. The SEM pictures of fracture surface provide a reliable evidence for the observed grain size effect on LCF behaviors for material. Based on the fractographic analysis, transgranular cracks dominate the LCF failure at 600 °C. For smaller grain size specimens with more grain boundaries, when it is subjected to external force, plastic deformation is more uniform and the stress and dislocations concentrate at grain boundaries. (3) The scattering band (i.e. the slope of the predicted LCF lifetime vs. tested data) is 5.49 reducing by about 10 times, indicating the grain size plays an important role in LCF lifetime prediction and the LCF lifetime can be described well with the modified SWT model. This modified model can make the fatigue test result with great dispersion be processed reasonably, so as to provide correct test data for appraisal of material fatigue and estimation of fatigue lifetime. Acknowledgements We acknowledge financial support from National Natural Science Foundation of China (NSFC) (Grant Nos. 51675024, 51305012 and 51375031). Reference [1] Wang, R., Li, D., Hu, D., et al., 2016. A Combined Critical Distance and Highly-Stressed-Volume Model to Evaluate the Statistical Size Effect of the Stress Concentrator on Low Cycle Fatigue of TA19 Plate. International Journal of Fatigue 95, 8-17. [2] Hall, E., 1951. The Deformation and Ageing of Mild Steel: III Discussion of Results. Proceedings of the Physical Society B64, 747. [3] Petch, N., 1953. The Cleavage Strength of Polycrystals. J Iron Steel Inst 174(1), 25--28. [4] Pieraggi, B., Uginet, J., 1994. Fatigue and Creep Properties in Relation with Alloy 718 Microstructure. Superalloys 535-544. [5] Spath, N., Zerrouki, V., Poubanne, P., et al., 2001. 718 Superalloy Forging Simulation: A Way to Improve Process and Material Potentialities. Journal of Japan Society of Perinatal and Neonatal Medicine 47, 951-955. [6] Merrick, H., 1974. The Low Cycle Fatigue of Three Wrought Nickel-Base Alloys. Metallurgical and Materials Transactions B 5(4), 891-897. [7] Jia, X., Lv, H., Yao, C., 2003. Fine-Grain Forming Process, Mechanism and Properties of GH4169 Alloy. Materials for Mechanical Engineering 27(1), 15-50. [8] Kobayashi, K., Yamaguchi, K., Hayakawa, M., et al., 2005. Grain Size Effect on High-Temperature Fatigue Properties of Alloy718. Materials Letters 59(2–3), 383-386. [9] Andersson, J., 2005. The Influence of Grain Size Variation on Metal Fatigue. International Journal of Fatigue 27(8), 847-852. [10] Sweeney, C. , O’Brien , B., Dunne, F., et al., 2014. Strain-Gradient Modelling of Grain Size Effects on Fatigue of Cocr Alloy. Acta Materialia 78(5), 341-353. [11] Zhang, K., Ju, J., Li, Z., et al., 2015. Micromechanics Based Fatigue Lifetime Prediction of A Polycrystalline Metal Applying Crystal Plasticity. Mechanics of Materials 85, 16-37. [12] Li, Z., Wang, Q., Luo, A., et al., 2015. Fatigue Behaviour and Life Prediction of Cast Magnesium Alloys. Materials Science and Engineering A 647, 113-126. [13] Alexandre, F., Deyber, S., Pineau, A., 2004. Modelling the Optimum Grain Size on the Low Cycle Fatigue Life of A Ni Based Superalloy in the Presence of Two Possible Crack Initiation Sites. Scripta Materialia 50(1), 25 – 30. [14] Zhao, R., Han, J., Liu, B., et al., 2016. Interaction of Forming Temperature and Grain Size Effect in Micro/Meso-Scale Plastic Deformation of Nickel-Base Superalloy. Materials and Design 94, 195-206. [15] Zhang, L., Wu, X., Huang, X., et al., 2014. Fractographical Investigation on High-Cycle Fatigue Behaviour Of Direct Aging GH4169 Superalloy. Materials Science Forum 789, 627-632. [16] Maderbacher, H., Oberwinkler, B., Gänser, H., et al., 2013. The Influence of Microstructure and Operating Temperature on the Fatigue Endurance of Hot Forged Inconel ®, 718. Components. Materials Science and Engineering A 585, 123-131. [17] Deng, G., Tu, S., Zhang, X., et al., 2016. Small Fatigue Crack Initiation and Growth Mechanisms of Nickel-Based Superalloy GH4169 at 650° C in Air. Engineering Fracture Mechanics 153, 35-49. [18] Du, W., Wang, W., Min, H., et al., 2009. Research on Low Cycle Fatigue Life of A Compressor Disc. Gas Turbine Experiment and Research. [19] Sattar, S., Sundt, C., 2015. Gas Turbine Engine Disk Cyclic Life Prediction. Journal of Aircraft 12(12), 360-365. [20] Smith, R., Watson, P., Topper, T., 1970. A Stress-Strain Function for the Fatigue of Metals. Journal of Materials 5(4), 767-778. [21] Fash, J., Socie, D., 1982. Fatigue Behavior and Mean Effects in Grey Cast Iron. International Journal of Fatigue 4(3), 137-142. [22] Socie, D., 1987. Multiaxial Fatigue Damage Models. Transactions of the ASME. Journal of Engineering Materials and Technology 109, 293 298. [23] Xing, X., 1999. A Statistical Theory of Transgranular Brittle Fracture for Metals. Acta Physica Sinica (1):107-113.

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