13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- to 0.28 mm for VТ1-0. The relation λр/λе, apparently, can serve as mechanical characteristics determining a relative contribution of the specimen plastic distortion into displacement caused by change in specimen ductility. 4. Conclusion A new method for determining crack toughness of materials is described based on test data of small-size chevron-notched specimens in terms of commercial titanium VT1-0 and titanium alloy VT6 with ultrafine-grained (UFG) structure, obtained by methods of severe plastic deformation (SPD). A problem of separating a part, connected with variations in specimen ductility under crack propagation, of the total displacement of load application point, is solved. A series of important computational problems connected with testing of chevron-notched specimens is solved in the study. Analytical expressions are obtained to calculate the Young’s modulus of the material and to determine specific fracture energy. The calculated values of the Young’s modulus Е and stress intensity factor KIc agree with known test data of standard specimens made of commercial titanium VТ1-0 and titanium alloy VТ6. The work was supported by Russian Foundation for Basic Research. Project № 08-10-01182-а. References 1. L.M. Barker, Theory for determining KIc from small, non-LEFM specimens, supported by experiments on aluminum. Int. J. of Fracture, 16, No. 6 (1979) 515-536. 2. C.T. Wang, R.M. Pillar, Short-rod elastic-plastic fracture toughness test using miniature specimens. J. Mater. Sci. 24 (1989) 2391-2400. 3. T.J. Grant, L. Weber, A. Mortensen, Plasticity in Chevron-notch fracture toughness testing. Engineering Fracture Mechanics, 67 (2000) 263-276. 4. B.A. Drozdovsky, T.V. Polischuk, V.P. Volkov, Chevron notch as a method of thickness decrease of the specimen at determining of КIc. Zavodskaya Laboratoriya, 6 (1987) 74-76. 5. R.R. Rakhimkulov, Matching of fracture toughness values of К1с, obtained in chevron-notched specimens and based on standard technique for the steel St3sp. Neftegazovoe Delo, 2 (2010) 1-10. http://www.ogbus.ru/authors/Rakhimkulov/Rakhimkulov_1.pdf 6. D. Broek, Fundamental concepts of fracture mechanics, Vysshaya shkola, Moskow, 1980. 7. G.A. Salischev, R.M. Galeev, S.P. Malysheva et al., Change in elasticity modulus at annealing of submicrocrystalline titanium, The Physics of Metals and Metallography (FMM), V. 85. No. 3 (1998) 178-181. 8. V.I. Betekhtin, O.R. Kolobov, M.V. Narykova et al., Mechanical properties, density and defect structure of submicrocrystalline titanium VТ1-0, obtained after severe plastic deformation at screw and lengthwise rolling. Journal of Technical Physics, 81, Iss. 11 (2011) 58-63. 9. M.D. Podscrebko, Resistance of materials, Vyseishaya shkola, Minsk, 2007. 10. S.P. Timoshenko, J. Gud’er. The theory of elasticity, Nauka, Moskow, 1975. 11. GOST 16483.9-73. Drevesina. Methods of elasticity modulus determination under static bending, Moskow, 1973.
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