PSI - Issue 13

Valeriy Lepov et al. / Procedia Structural Integrity 13 (2018) 1201–1208 Valeriy Lepov et al/ Structural Integrity Procedia 00 (2018) 000 – 000

1208

8

4. Conclusion The microstructure analysis shown the significance of inhomogeneity for mechanical properties, lifetime and prospect recycling possibilities of steel. The experimental testing of locomotive tire steel shows the impact toughness drop at low temperature conditions. The microstructural study for weld joints reveals the small cracks in heat affected zone, so the size and distance between such defects are used for stochastic modeling visualization of crack propagation and crack velocity estimation. The revealing mechanisms and proposed relationships could be used for theoretical and numerical modeling of damage accumulation and fracture in welded steel structures and machines. Fractal dimension of surface images increased from in as-received condition steel probes to hardening material and steel after long usage and hardening processed. So the initial phase and structure inhomogeneity of steel could influence the mechanical properties after the hardening by severe plastic deformation process. The new criterion and approach of damage estimation for locomotive tire in extreme uncertainty conditions are offered. It is revealed that the lifetime of tire is significantly sensitive to impact strength at low temperature during operation. In case of presence of some defects in welded zone or between the welded and heat affected zone (or base metal) the crack will grow rapidly. Actually the energy dissipation in the welded zone is half the value in base metal. To avoid the catastrophic failure of welded structures, special techniques should be applied to reduce hardness of the material. Systematic monitoring of structures like railway, locomotive tire, bridges, pipe lines, energy stations and buildings is necessary. One of the good methods of non-destructive testing could be microhardness control of the weld and heat affected zone to avoid the significant modification of mechanical properties of welded structures. Acknowledgements This research has been partially supported by Russian Foundation for Basic Research (Project 18-48-140015) and Federal Agency of Scientific Organization of Ministry of Science and Education of Russian Federation. The authors are also hereby thankful to Larionov’s IPTPN SB RAS scientists Dr. Susanna Makharova from Material Science Department for help in microstructure and microhardness analysis and Dr. Afanasiy Ivanov from Fracture Modeling Department for provision of St3sp probes. References Al-Najjar, N.I., Weinstein J., 2015, A Bayesian model of Knightian uncertainty, Theory Dec. 78, 1 – 22. Arkhangelskaya, E.A., Lepov, V.V., Larionov, V.P., 2003, The Role of Defects in the Development of Delayed Fracture of a Damaged Medium under the Effect of Hydrogen, Materialovedenie 8, 7 – 10. Broberg, K.B., 1990, Computer demonstration of crack growth, Int. J. Fracture 42, 277-285. Broek, D., 1982, Elementary engineering fracture mechanics, Martinus Nijhoff Publishers, Boston. Cherepanov, G.P., 1974, Mechanics of Brittle Fracture, Nauka Press, Moscow. Bell, J. F., 1973, Mechanics of Solids. Volume I: The Experimental Foundations of Solid Mechanics. Springer-Verlag Berlin Heidelberg Computational and Experimental Methods in Structures: Vol.3. Multiscale Modeling in Solid Mechanics, 2009, ed. Ugo Galvanetto and M.H. Ferri Aliabadi, World Scientific, London. Fracture. An Advanced Treatise, ed. Liebovitz, H., 1968, Academic Press, New York and London. Fracture at all Scales, ed. Pluvinage, Guy, Milovic, Ljubica, 2017, Springer International Publishing Ghomashchi, M.R., 1998, Quantitative microstructural analysis of M2 grade high speed steel during high temperature treatment, Acta Materialia, 46, 14, 5207-5220. Goryacheva, I.G., Soshenkov, S.N., and Torskaya, E.V., 2013, Modelling of Wear and Fatigue Defect Formation in Wheel-Rail Contact, Vehicle Syst. Dyn. 51, 6, 767 – 783. Griffith, A.A., 1920, The phenomenon of rupture and flow in solids, Phil. Trans. Roy. Soc. Ser. A 221, 163 – 198. Hell, S.W., et al, 2015, The 2015 super-resolution microscopy roadmap, J. Phys. D: Appl. Phys. 48, 443001 Ιοffe, A.F., 1928, The Physics of Crystals, McGraw Hill, New York and London. Lepov, V., Ivanova, A., Achikasova, V., Lepova, K., 2007, Modeling of the damage accumulation and fracture: structural-statistical aspects, Key Engineering Materials 345-346, I, 809-812. Lepov, V.V., et al., 2008, The Mechanism of Nanostructured Steel Fracture at Low Temperatures, Nanotechnologies in Russia 3, 734 – 742 Lepov, V.V., Loginov, A.B., 2012, Non-Markovian evolution approach to structural modeling of material fracture, World J. of Engng 9(3), 207-212. Lepov, V., Grigoriev, A., Achikasova, V., Lepova, K., 2016, Some Aspects of Structural Modeling of Damage Accumulation and Fracture Processes in Metal Structures at Low Temperature, Modelling and Simulation in Engineering 2016, 7178028. Lepov, V., Grigoriev, A., Bisong M., Lepova K., 2017, Brittle Fracture Modeling for Steel Structures operated in the Extreme, Structural Integrity Procedia 5, 777-784.