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P. Gallo et alii, Frattura ed Integrità Strutturale, 34 (2015) 180-189; DOI: 10.3221/IGF-ESIS.34.19 189  The decrement of the fatigue life of the specimens with rough surfaces at high temperature suggests this result is originated from the reduction in the number of cycles for crack initiation and it is clear the beneficial effect of the surface roughness on the fatigue behaviour.  The ratio between N i (number of cycles to crack initiation) and N (number of cycles to failure) is always greater than 0.8, for all of the surface roughness values, proving that a large fraction of the fatigue life is spent in the crack initiation phase. R EFERENCES [1] Krukemyer, T.H., Fatemi, A., Swindeman, R.W., Fatigue Behavior of a 22Cr-20Ni-18Co-Fe Alloy at Elevated Temperatures, J. Eng. Mater. Technol., 116 (1994) 54. DOI:10.1115/1.2904255. [2] Kobayashi, H., Todoroki, a, Oomura, T., Sano, T., Takehana, T., Ultra-high-cycle fatigue properties and fracture mechanism of modified 2.25Cr-1Mo steel at elevated temperatures, Int. J. Fatigue., 28 (2006) 1633-1639. DOI:10.1016/j.ijfatigue.2005.08.016. [3] Fan, Z., Chen, X., Chen, L., Jiang, J., Fatigue-creep behavior of 1.25Cr0.5Mo steel at high temperature and its life prediction, Int. J. Fatigue, 29 (2007) 1174-1183. DOI:10.1016/j.ijfatigue.2006.07.008. [4] Chen, Q., Kawagoishi, N., Nisitani, H., Evaluation of notched fatigue strength at elevated temperature by linear notch mechanics, Int. J. Fatigue, 21 (1999) 925-931. DOI:10.1016/S0142-1123(99)00081-X. [5] Kawagoishi, N., Chen, Q., Nisitani, H., Fatigue strength of Inconel 718 at elevated temperatures, Fatigue Fract. Eng. Mater. Struct., 23 (2000) 209-216. DOI:10.1046/j.1460-2695.2000.00263.x. [6] Berto, F., Gallo, P., Lazzarin, P., High Temperature Fatigue Tests of a Cu-Be Alloy and Synthesis in Terms of Linear Elastic Strain Energy Density, Key Eng. Mater., 627 (2014) 77-80. DOI:10.4028 /www.scientific.net/KEM.627.77. [7] Shi, D.Q., Hu, X.A., Wang, J.K., Yu, H.C., Yang, X.G., Huang, J., Effect of notch on fatigue behaviour of a directionally solidi fi ed superalloy at high temperature, (2013) 1288-1297. DOI:10.1111/ffe.12065. [8] Berto, F., Lazzarin, P., Gallo, P., High-temperature fatigue strength of a copper-cobalt-beryllium alloy, J. Strain Anal. Eng. Des., 49 (2014) 244-256. DOI:10.1177/0309324713511804. [9] Gallo, P., Berto, F., Lazzarin, P., High temperature fatigue tests of notched specimens made of titanium Grade 2, Theor. Appl. Fract. Mech., In press (2015). DOI:10.1016/j.tafmec.2014.12.007. [10] Louks, R., Susmel, L., The linear-elastic Theory of Critical Distances to estimate high-cycle fatigue strength of notched metallic materials at elevated temperatures, Fatigue Fract. Eng. Mater. Struct., (2014) In press. DOI:10.1111/ffe.12273. [11] Kim, J.J., Nam, S.W., Ryu, J.H., The sensitivity of surface crack initiation to surface roughness in low-cycle fatigue at high temperature, Mater. Sci. Eng. A., 130 (1990) L7-L10. DOI:10.1016/0921-5093(90)90069-F. [12] Ryu, J., Nam, S., Effect of surface roughness on low-cycle fatigue life of Cr-Mo-V steel at 550 °C, Int. J. Fatigue, 11 (1989) 433-436. DOI:10.1016/0142-1123(89)90183-7. [13] Berto, F., Lazzarin, P., Marangon, C., Fatigue strength of notched specimens made of 40CrMoV13.9 under multiaxial loading, Mater. Des., 54 (2014) 57-66. DOI:10.1016/j.matdes.2013.08.013. [14] Hussain, K., Wilkinson, D.S., Embury, J.D., Effect of surface finish on high temperature fatigue of a nickel based super alloy, Int. J. Fatigue, 31 (2009) 743-750. DOI:10.1016/j.ijfatigue.2008.03.033. [15] Gao, Y.K., Li, X. Bin, Yang, Q.X., Yao, M., Influence of surface integrity on fatigue strength of 40CrNi2Si2MoVA steel, Mater. Lett., 61 (2007) 466-469. DOI:10.1016/j.matlet.2006.04.089. [16] Lazzarin, P., Sonsino, C.M., Zambardi, R., A notch stress intensity approach to assess the multiaxial fatigue strength of welded tube-to-flange joints subjected to combined loadings, Fatigue Fract. Eng. Mater. Struct., 27 (2004) 127-140. DOI:10.1111/j.1460-2695.2004.00733.x. [17] Latella, B.A., Humphries, S.R., Young’s modulus of a 2.25Cr-1Mo steel at elevated temperature, Scr. Mater., 51 (2004) 635-639. DOI:10.1016/j.scriptamat.2004.06.028. [18] Lazzarin, P., Berto, F., Some Expressions for the Strain Energy in a Finite Volume Surrounding the Root of Blunt V- notches, Int. J. Fract., 135 (2005) 161-185. DOI:10.1007/s10704-005-3943-6.