Issue34

A. Shanyavskiy, Frattura ed Integrità Strutturale, 34 (2015) 199-207; DOI: 10.3221/IGF-ESIS.34.21 206 Figure 9 . Ratio between crack growth period and durability N p /N f against durability N f for the tested specimens after different termomechanical procedures C ONCLUSION 1. Test results of specimens manufactured from billets and rods of titanium alloy VT3-1 with two-phase (  ) globular and lamellar structure have shown that, in the range of cyclic stress near “fatigue limit”, there exists transition from HCF regime to VHCF regime. 2. Crack path of “run-out specimens” not failed under cyclic tests and, then, tensed up to failure have fractographically been analysed. That has revealed fracture surface pattern related to VHCF regime with subsurface crack origination for different combination of tempering and surface hardening procedures. 3. Relationship between crack growth period and durability N p /N f against durability N f for the tested specimens after different termomechanical procedures has the same tendency, and it can be used in practice to estimate the crack growth period in VHCF regime where fatigue striations have not evidence on the fracture surface. R EFERENCES [1] Mughrabi ,H., Specific features and mechanisms of fatigue in the ultrahigh-cycle regime, Int. Journ. Fatigue, 28 (2006) 1501–1508. [2] Panin, V.E., Panin A.V., Effect of surface layer in deformed solid body. Physical Mesomechanics, 8(5) (2005) 7-15. [3] Shanyavskiy, A.A., Fatigue limit - Material property as an opened or closed system? Practical view on the aircraft components failures in GCF area. Int. J. Fatigue, 28(11) (2006) 1647 – 1657. [4] Sakai, T., Ochi Y. (Eds) Very High Cycle Fatigue, Proc. Third Intern Conf VHCF-3, September 16-19, 2004, Ritsumeikan University, Kusatsu, Japan, (2004). [5] Bathias, C., Paris, P.C., Gigacycle fatigue in mechanical practice, Marcel Dekker, NY, USA, (2005) [6] Shanyavskiy, A.A., Losev, A.I., The effect of loading waveform and microstructure on the fatigue response of titanium aero-engine compressor disk alloys. Fatigue Fracture Engng Mater. Struct., 26 (2003) 329-342. [7] Suh, C.-M., Hawing, B.W., Kim, S.C., Lee, T.S., A study on the fatigue characteristics of bearing steel in gigacycles. Proc. Third Intern Conf VHCF-3 (Sakai T. and Ochi Y. Eds), Ritsumeikan University, Kusatsu, Japan, (2004) 593- 600. [8] Liantao, L., Kazuaki, S., Effect of two-step load variation on gigacycle fatigue and internal crack growth behavior of high carbon-chromium bearing steel. Proc. Third Intern Conf VHCF-3 (Sakai T. and Ochi Y. - Eds), Ritsumeikan University, Kusatsu, Japan, (2004) 185-192. [9] Shanyavskiy, A.A., Banov, M.D., The twisting mechanism of subsurface fatigue cracking in Ti–6Al–2Sn–4Zr–2Mo– 0.1Si alloy, Engng Fracture Mechanics, 77 (2010) 1896–1906.