PSI - Issue 19

Shota Hasunuma et al. / Procedia Structural Integrity 19 (2019) 194–203 Shota Hasunuma, Ogawa Takeshi/ Structural Integrity Procedia 00 (2019) 000 – 000

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conservatively predict fatigue life when there is variation in the surface shape due to the turning process. In addition, this method has the advantage that we can predict the fatigue life without measuring the scratch depth.

5. Conclusions Low cycle fatigue tests were performed for SUS316L austenitic stainless steel to reveal the effect of the machined surface layer on low cycle fatigue life. We then proposed a method for predicting the low cycle fatigue life of a component with a machined surface layer. The following aspects are clarified by the results. (1) Residual stress and variation in the material property did not affect the low cycle fatigue life. However, scratches strongly affected the low cycle fatigue life. (2) A method for predicting the low cycle fatigue life of a component having a variation in surface shape was investigated. The effect of machined surface layer was modeled by the initial crack size. Predictions of the fatigue life using the real crack size were similar to or longer than experimental results, because the measured crack depth was smaller than the real crack depth. (3) The prediction method was modified so that the initial crack depth was determined from the initial surface crack length under the assumption of a semicircular crack shape. The predicted fatigue life then became shorter than the experimental results. This method can conservatively predict the fatigue life when there is a variation in surface shape due to the turning process. References Dowling, NE., 1977. Crack Growth during Low-Cycle Fatigue of Smooth Axial Specimens. American Society for Testing and Materials Special Technical Publication 637, 97 – 121. Hasunuma, S., Isosaki, Y., Kiritani, S., Hatano, A., Izumi, S., Sakai, S., 2015. Effect of machined surface condition on fatigue strength of Ni based superalloy Alloy 718. Transactions of the JSME 81, 15-00328. Hasunuma, S., Ogawa, T., 2014. Initiation and Growth of Small Fatigue Cracks of Steels Used for Nuclear Power Plants Under Low Cycle Regime. Proceedings of ASME Pressure Vessels and Piping Conference, PVP2014-28237. Hasunuma, S., Miyata, Y., Ogawa, T., Sakaue, K., 2011a. Effect of Pre-strain on Low Cycle Fatigue Strength of Austenitic Stainless Steel SUS316NG. Transactions of the Japan Society of Mechanical Engineers Series A 77, 843 851. Hasunuma, S., Miyata, Y., Sakaue, K., Ogawa, T., 2011b. Effect of Pre-strain History on Small Crack Growth under Low Cycle Fatigue for JIS SFVQ1A Steel. Journal of the Society of Materials Science 60, 210-216. Japan Society of Mechanical Engineering, 2012, Codes for Nuclear Power Generation Facilities: Rules on Design and Construction for Nuclear Power Plants, JSME S NC1-2012. Kamaya, M., Kawakubo, M., 2010. Damage Due to Low-cycle Fatigue of Type 316 Stainless Steel : Fatigue Life under Variable Loading and Influence of Internal Cracks. Transactions of the Japan Society of Mechanical Engineers Series A 76, 1048-1058. Kozokenzensei hyouka handbook henshuiinkai, 2005. Kozokenzensei Hyouka Handbook. Kyoritsu Shuppan, Tokyo, p.334. Newman, J. C., Raju, I.S., 1984. Stress-intensity Factor Equations for Cracks in Three-dimensional Finite Bodies Subjected to Tension and Bending Loads, NASA Technical Memorandum 85793. Ozeki, H., Hasunuma, S., Ogawa, T., 2013. The Effect of Variable Amplitude Strain Conditions on Low Cycle Fatigue Strength of Stainless Steel SUS316L. Journal of the Society of Materials Science 62, 201-206. Sakakibara, Y., Kubushiro, K., Nakayama, H., 2010. Distribution of Misorientation at Grain Boundary by EBSD for Low Carbon Stainless Steel Strained by Various Deformation Modes, Journal of the Japan Institute of Metals and Materials 74, 258-263. Suresh, S., 2005. Fatigue of Materials 2nd ed. Cambridge University Press, Cambridge, p.12.