Issue 49

M. Bannikov et alii, Frattura ed Integrità Strutturale, 49 (2019) 383-395; DOI: 10.3221/IGF-ESIS.49.38 394 second harmonic of displacements in the experiment gives adequate information about the accumulation of damage in the material. C ONCLUSION n analysis of the free end oscillations during gigacyclic tests showed a significant increase in the second harmonic amplitude and nonlinearity coefficient during the formation of fatigue cracks. In conjunction with the simulation results, we can conclude that the deviation from the linear-elastic law (“anomaly of elastic compliance”) is due to the accumulation of defects in the material, and the avalanche-like growth of the second harmonic displacement corresponds to the avalanche-like growth of defects and the formation of a macroscopic crack. Thus, it is possible to judge the accumulation of damage, including - in the amount of material based on the acoustic signal. Using the proposed equations, it can to predict the fatigue life of the material and identify internal defects and cracks before macroscopic destruction occurs. A CKNOWLEDGMENTS uthors thank Prof. Valery Matveyenko for the proposal to present the paper in the issue. This work was supported by the Russian Science Foundation, grant number 18-72-00142. R EFERENCES [1] Botvina, L.R. (2004) Gigacycle fatigue is a new problem in physics and mechanics of destruction // Factory Laboratory. Diagnostics of materials 70(4), pp. 41. (In Russian). [2] Bathias, C., Paris, P.C. (2005), Gigacycle Fatigue in Mechanical Practice, Marcel Dekker Publisher Co., pp. 328. [3] Oborin, V., Bannikov, M., Naimark, O., Palin-Luc, T. (2010). Scaling invariance of fatigue crack growth in gigacycle loading regime, Technical Physics Letters, 36 (11), pp. 1061-1063. DOI: 10.1134/S106378501011026X. [4] Cowles, B.A. (1996). High cycle fatigue in aircraft gas turbines - an industry perspective, International Journal of Fracture 80, pp.147-163. DOI: 10.1007/BF00012667. [5] Shanyavsky, A.A. (2007) Simulation of fatigue damage of metals. Synergetic in aviation, Ufa: Monograph LLC. (In Russian). [6] Nicholas, T. (2006). High Cycle Fatigue. A Mechanics of Material Perspective, Elsevier., pp. 641. [7] Peters, J.O., Ritchie, R.O. (2000). Influence of foreign object damage on crack initiation and early crack growth during high-cycle fatigue of Ti-6Al-4V, Eng. Fract. Mech. 67, pp. 193-207. DOI: 10.1016/S0013-7944(00)00045-X. [8] Spanrad, S., Tong, J. (2011). Characterisation of foreign object damage (FOD) and early fatigue crack growth in laser shock peened Ti–6Al–4V aerofoil specimens, Materials Science and Engineering A, 528, pp. 2128–2136. DOI: 10.1016/j.msea.2010.11.045. [9] Oakley, S.Y., Nowell, D. (2007) Prediction of the combined high- and low-cycle fatigue performance of gas turbine blades after foreign object damage, International Journal of Fatigue, 29, pp. 69–80. DOI: 10.1016/j.ijfatigue.2006.02.042. [10] Chen, Xi (2005). Foreign object damage on the leading edge of a thin blade, Mechanics of Materials, 37, pp. 447–457. DOI: https://doi.org/10.1016/j.mechmat.2004.03.005. [11] Nowell, D., Duó, P., Stewart, I.F. (2003). Prediction of fatigue performance in gas turbine blades after foreign object damage, International Journal of Fatigue, 25, pp. 963-969. DOI: 10.1016/S0142-1123(03)00160-9. [12] Mughrabi, H. (2015). Microstructural mechanisms of cyclic deformation, fatigue crack initiation and early crack growth, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 373(2038), 20140132. DOI: 10.1098/rsta.2014.0132. [13] Zhang, Li-Li, et al. (2016). On the formation mechanisms of fine granular area (FGA) on the fracture surface for high strength steels in the VHCF regime, International Journal of Fatigue, 82, pp. 402-410. DOI: 10.1016/j.ijfatigue.2015.08.021. A A