PSI - Issue 2_B

Chretien Gaëlle et al. / Procedia Structural Integrity 2 (2016) 950–957

957

8

Gaëlle Chretien et al. / Structural Integrity Procedia 00 (2016) 000–000

 Short crack effect seems limited to crack with length shorter than 3mm at 20°C and 2mm at 400°C. This effect is attributed to the difference on crack closure level between short and long crack as shown by the evolution of K op .  Kitagawa diagram models proposed by El Haddad correctly fit the Δσ th vs. Δa plot even if a 0 can not be related to a microstructural scale. On the contrary, Chapetti’s model uses the size of the strongest microstructural barrier, but is not able to fit the bend. It requires to better study crack closure by analyzing roughness and oxide thickness and by undertaking experiments in vacuum environment in order to uncouple plasticity induced crack closure. This information will allow us to apply the approach proposed by Maierhofer.  The better understanding of crack closure phenomenon will enable to determine if it is possible to interpolate the effect of short crack between 20°C and 400°C and how make it. Acknowledgements Turbomeca-SAFRAN group is gratefully acknowledged for financial support and for providing the material. References ASTM E647-00, Standard Test Method for Measurement of Fatigue Crack Growth Rates. ASTM International, 2000. Berata, W., 1992. Résistance à la fissuration en fatigue à température élevée de l’alliage TA6V, Thèse Université de Poitiers. Brown, C.W., Hicks, M.A., 1983. A study of short fatigue crack growth behavior in Titanium alloy IMI 685. Fatigue & Fracture of Engineering Materials & Structures 6, 67–76. Chapetti, M.D., 2005. Application of a threshold curve model to high-cycle fatigue behavior of small cracks induced by foreign-object damage in Ti–6Al–4V. International Journal of Fatigue 27, 493–501. Elber, W., 1970. Fatigue crack closure under cyclic tension. Engineering Fracture Mechanics 2, 37–45. El Haddad, M.H., Topper, T.H., Smith, K.N., 1979. Prediction of non propagating cracks. Engineering Fracture Mechanics 11, 573-584. James, M.R., Morris, W.L., 1988. Effect of Fracture Surface Roughness on Growth of Short Fatigue Cracks. Metallurgical Transactions A 14, 153-155. Kikukawa, M., Jono, M., Mikami, S., 1982. Fatigue crack propagation and crack closure behavior under stationary vary loading-test results of aluminium alloy. Journal of the Society of Materials Science 31, 438–487. Kim, C.Y., 2006. A procedure for determining crack opening load from differential displacement data. Materials Science and Engineering A 416, 176-180. Kitagawa, H., Takahashi, S., 1976. Applicability of fracture mechanics to very small cracks or the cracks in the early stage. In: Proc. 2nd International Conference on Mechanical Behavior of Materials, Boston, ASM, Cleveland, Ohio, 627–631. Lankford, J., Ritchie, R.O., 1986. Small Fatigue Cracks. TMS AIME publication, Warendale, Pensilvania, USA. Maierhofer, J., Pippan, R., Gänser, H.-P., 2014. Modified NASGRO equation for physically short cracks. International Journal of Fatigue 59, 200–207. McClung, R.C., Sehitoglu, H., 1988. Closure behavior of small cracks under high strain fatigue histories. In: J. C. Newman Jr., W. Elber editors, Mechanics of Fatigue Crack closure. ASTM STP, 279-299. McEvily, A.J., Endo, M., Murakami, Y., 2003. On the area relationship and the short fatigue crack threshold. Fatigue & Fracture of Engineering Materials & Structures 26, 269-278. Miller, K.J., 1982. The short crack problem. Fatigue & Fracture of Engineering Materials & Structures 5, 223-232. Newman Jr, J.C., Elber, W., 1988. Mechanics of fatigue crack closure, ASTM STP 982. American Society for Testing and Materials, Philadelphia, USA. Oberwinkler, B., Lettner, A., Eichlseder, W., 2011. Multiscale fatigue crack observations on Ti–6Al–4V. International Journal of Fatigue 33, 710–718. Pearson, S., 1975. Initiation of fatigue cracks in commercial aluminium alloys and the subsequent propagation of very short cracks. Engineering Fracture Mechanics 7, 235-247. Petit, J., 1999. Influence of environment on small fatigue crack growth, in “Small Fatigue Cracks, Mechanics, Mechanisms and Applications”. In: K.S. Ravichandran, R.O. Ritchie and Y. Murakami eds., Elsevier Pub., 167-178. Pineau, A., 1986. Short fatigue crack behaviour in relation to three dimensional aspects and crack closure effect. Lankford J and Ritchie RO eds TMS AIME pub Warrendale, Pennsylvania, USA, 191-209. Ravichandran, K.S., Ritchie, R.O., Murakami, Y, 1999. Small fatigue cracks: mechanics and mechanisms. Engineering Foundation publication. Ritchie, R.O., Yu, W., 1986. Short crack effecting fatigue: a consequence of crack tip shielding. Small fatigue cracks. Lankford J and Ritchie RO editors TMS AIME pub Warrendale, Pennsylvania, USA, 167-189. Sinha, V., Mercer, C., Soboyejo, W.O., 2000. An investigation of short and long fatigue crack growth behavior of Ti–6Al–4V. Materials Science and Engineering A 287, 30–42. Suresh, S., Ritchie, R.O., 1984. Propagation of short fatigue cracks. International Materials Reviews 29, 445-476. Tokaji, K., 2006. High cycle fatigue behaviour of Ti–6Al–4V alloy at elevated temperatures. Scripta Materialia 54, 2143–2148. Zeghloul, A., Petit, J., 1989. Influence de l’environnement sur la propagation des fissures courtes et longues dans un alliage léger type 7075. Revue de Physique 24, 893–904.