PSI - Issue 20

A.A. Alexeev et al. / Procedia Structural Integrity 20 (2019) 254–258 A.A. Alexeev et al / Structural Integrity Procedia 00 (2019) 000 – 000

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4. Conclusion According to the measurement results, it has been established that in polymers the crack velocity at the branching of a single crack is 500-800 m / s, at multiple branching with parallel movement of the front of several cracks it is 750-920 m / s. It is shown for the first time, that crack branching velocity coincide for single and multiple crack branching, and this velocity is limiting. The results show that of crack branching velocity is critical (limiting) velocity of crack propagation, and the energy entering the top of a moving crack is spent not on increasing the crack velocity, but on creating new cracks by branching, which confirms the proposed hypothesis of the physical mechanism of crack branching. Further, it is necessary to carry out work on measuring of crack branching velocity in steels, studying the physical mechanism of crack branching in polymers and steels, and evaluating the suitable criterion for crack branching from the point of view of both physics and mechanics of fracture. References 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. JTF Letters 26, 67-77. 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. 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. Yoffe, E., 1951. The moving Griffith crack. Philosophical Magazine 42, 739 – 750.