PSI - Issue 30

A.A. Alexeev et al. / Procedia Structural Integrity 30 (2020) 1–5 A.A. Alexeev et al. / Structural Integrity Procedia 00 (2020) 000–000

5

5

4. Conclusion A technique has been developed, an installation has been created for measuring the velocity of propagation and branching of a cracks. According to the measurement results, it was found that the crack branching velocity in steel is 679-746 m / s, which correlates with crack branching velocity in polymers 500-800 m / s. The results show that the crack branching velocity is a critical (limiting) crack propagation velocity, and the energy entering the top of a moving crack is not spent on increasing the crack velocity, but on creating new cracks by branching, which confirms the hypothesis of the physical crack branching mechanism. Achieving a critical velocity V* for crack branching is a sufficient condition , and a necessary condition is the excess of the energy flow entering the top of the moving crack over the energy of the material’s resistance to the growth of a single crack G*, when the material in the fracture zone does not have time to dissipate the energy released during the crack propagation through the damage mechanisms inherent in the material (microcracking for polymers, intragranular chips for steel). Acknowledgements The authors are grateful for the support of the work of the Larionov Institute of the Physical-Technical Problems of the North SB RAS and funded by Ministry of Science and Education of Russian Federation, Project III.28.1.1 in the frames of Program for Basic Research of the Siberian Branch of Russian Academy of Sciences. References Alexeev, A.A., Syromyatnikova, A.S., Levin, A.I., 2013. Fracture mechanisms during crack branching. Part 1. Amorphous polymer. World Applied Sciences Journal 24(4), 414-420. Alexeev, A.A., Syromyatnikova, A.S., Bolshev, K.N., Ivanov, V.A., 2013. Fracture mechanisms during crack branching. Part 2. Steel. World Applied Sciences Journal 24(4), 421-428. Alexeev, A.A., Syromyatnikova, A.S., Bolshev, K.N., Bolshakov, A.M., Ivanov, V.A., Andreev, A.S., 2017. Crack branching criteria: crack velocity, Deformaciya i razhrushenie materialov 12, 2-7. Alexeev, A.A., Bolshev, K.N., Ivanov, V.A., Syromyatnikova, A.S., Bolshakov, A.M., Andreev, A.S., 2018. Experimental study of the crack branching velocity in polymers, Zavodskaya laboratoria. Diagnostika materialov 84(4), 60-65. Duffy, A.R., McClure, G.M., Eiber, R.J., Massey, W.A., 1969. Fracture. Edited by H. Liebowitz. New York: Academic Press, Volume 5, pp.159. Bedii, I.N., 1991. Investigation of crack kinetics in PMMA using dynamic photoelasticity, Strength problems 9, 40-46. Finkel, V.M., 1970. Fracture physics. Moscow: Metallurgiya, pp. 376. Kobayashi, A.S., Ramulu, M., 1985. Mechanics of crack curving and branching – a dynamic fracture analysis, International Journal of Fracture 27, 187-201. Naimark, O.B., Barannikov, V.A. Davydova, M.M., 2000. Dynamic stochasticity and scaling on the propagation of cracks, Pisma v JTF 26(6), 67-77. Ravi-Chandar, K., Knauss, W.G., 1984. An experimental investigation into dynamic fracture. I. Crack initiation and arrest, International Journal of Fracture 25, 247-262. Ravi-Chandar, K., Knauss, W.G., 1984. An experimental investigation into dynamic fracture. II. Microstructural aspects, International Journal of Fracture 26, 65-80. Ravi-Chandar, K., Knauss, W.G., 1984. An experimental investigation into dynamic fracture. III. On steady-state crack propagation and crack branching, International Journal of Fracture 26, 141-154. Ravi-Chandar K., 1998. Dynamic fracture of nominally brittle materials, International Journal of Fracture 90, 83-102. Sharon, E., Fineberg, J., 1996. Microbranching instability and the dynamic fracture of brittle materials, Physical Review B 54(10), 7128-7139. Serensen, S.V., Nemets, Ya., Strelyaev, V.S., 1970. The strength of plastics. Moscow: Mashinostroenie, pp. 335. Sheng, J.S., Zao, Ya-Pu., 1999. Two critical crack propagating velocities for PMMA fracture surface, International Journal of Fracture 98, 9-14. Uvarov, S.V., 2000. Experimental study of the effects of the nonlinear dynamics of crack propagation, Avtoreferat. disser. kand. tech. nauk, Perm: IMSS UrO RAN, pp.16.