PSI- Issue 9

Khadija Kimakh et al. / Procedia Structural Integrity 9 (2018) 243–249 Khadija.KIMAKH / Structural Integrity Procedia 00 (2018) 000–000

249

7

more and more pronounced with the increase in the feed rate. Consequently, these defects generate stress concentrations or micro cracks, which produce a decrease in fatigue life. Surarachai et al. (2008) analyzed the influence of the surface condition on the fatigue life of the 7010 aluminum alloy tested in 4-point bending. They explained the strong dependence between the surface roughness and the fatigue strength by the stress concentration generated by the roughness streaks.N.A.Alang (2011) studied the effect of surface condition on fatigue behavior. The roughness was varied over three levels (1.77, 2.88, 5.48 μm). He found that for lifetimes less than 10 5 cycles, no significant difference had been recorded, but beyond 10 5 cycles, low roughness specimens had a longer lifetime than rough specimens. Finally, we can conclude that the fatigue behavior of the materials is influenced by the surface integrity which is a direct result of the machining process. 4. Conclusion This study presents an experimental approach to highlight a correlation between the feed rate and the fatigue performance of the AISI 1045 steel parts obtained by turning process. Three batches of fatigue specimen were machined with three different values of feed rate ( 0.25 mm/rev, 0.15 mm/rev and 0.05 mm/rev), Then tested on uniaxial fatigue with a stress ratio R=0.1. The S-N curves registered present a marked gab that illustrates the significant effect of feed rate on fatigue lifetime of fatigue specimen. In fact, a variation in the feed rate affects directly the surface roughness of the specimens which generates local stress concentrations. The level of these concentrations governs the damage process. For σ max =550MPa, an increase of feed rate from f = 0.25 mm/rev to f = 0.15 mm/rev leads to 30% of increase of fatigue lifetime and 184% of the increase of feed rate from 0.15 mm/rev to f = 0.05 mm/rev. Also it can be concluded that:  The effect of feed rate is very significant for feed rate higher than 0.15mm/rev.  The effect of feed rate is more pronounced for low-stress levels.  The fatigue lifetime of parts obtained by turning process improves with the decrease of feed rate. Alang, N.A., Razak, N.A., Miskam, A.K. 2011. Effect of Surface Roughness on Fatigue Life of Notched Carbon Steel. International Journal of Engineering & Technology 11, 160-163. Choi, Y. 2015. Influence of feed rate on surface integrity and fatigue performance of machined surfaces. International Journal of Fatigue 78, 46 52. Davies, D. P., Jenkinsa, S. L. Legga, S. J. 2014.The Effect Machining Processes can have on the Fatigue Life and Surface Integrity of Critical Helicopter Components. Procedia CIRP 13, 25-30. Liu, G., Huang, G., Zou, B., Wang, X., Liu, Z., 2016. Surface integrity and fatigue performance of 17-4PH stainless steel after cutting operations. Surface & Coatings Technology 307, 182-189. Novovic, D., Dewes, R.C., Aspinwall, D.K., Voice, W., Bowen, P. 2004. The effect of machined topography and integrity on fatigue life. International Journal of Machine Tools & Manufacture 44, 125-134. Suraratchai, M., Limido, J., Mabru, C., Chieragatti, R. 2008. Modelling the influence of machined surface roughness on the fatigue life of aluminium alloy. International Journal of Fatigue 30, 2119–2126. Suraratchaï, M., Mabru, C., Chieragatti, R., Rezai, F.A. 2005. Influence de gammes d'usinage sur la tenue en fatigue d'un alliage léger aéronautique. 17ème Congrès Français de Mécanique. Troyes, France. Zhang, M., Wang, W., Wang, P., Liu, Y., Li, J., 2016. The fatigue behavior and mechanism of FV520B-I with large surface roughness in a very high cycle regime. Engineering Failure Analysis 66, 432-444. References