PSI - Issue 28

A.M. Bragov et al. / Procedia Structural Integrity 28 (2020) 2174–2180 Author name / Structural Integrity Procedia 00 (2019) 000–000

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In figure 5 shows a comparison of the average deformation diagrams in the stress-time axes obtained at classical processing of experimental data as well as using the dispersion shift procedure and a pulse shaper. Since the strain rate changes during the test, it is better to take the stress rate as a parameter estimating the similarity of loading conditions, which can be defined as the tangent of the slope of the ascending branch of the diagram σ s (t) . To obtain diagrams with a close slope of the ascending branch, the striker velocity was significantly higher in the experiments using the pulse shaper. It is seen that the application of the dispersion shift procedure has practically no effect on the value of the fracture stress of the test material. Besides, the difference between the maximum stresses when using the pulse shaper and without it is not more than 10% at the same stress rates. 4. Conclusions As a result of the research performed, the following conclusions can be drawn. Firstly the application of the dispersion shift procedure makes it possible to improve the quality of processing the experimental data obtained during testing of brittle media by the Kolsky method and to achieve more quality implementation of the main premise of the SHPB method. Secondly the difference between the maximum stresses when using the pulse shaper and without it is not more than 10%, but to achieve high stress and strain rates in experiments with a pulse shaper, a much higher striker velocity is required. The results obtained are testifying that it is possible to use the classical test of the SHPB and traditional processing of experimental data to assess the strength of brittle solids. Acknowledgements The experimental investigations of fine-grained concrete were carried out with the financial support of RFBR (grant 19-38-90225). Numerical procedure of dispersion shift of pulses in the measuring bars was supported by the Ministry of Science and Higher Education of the Russian Federation (task 0729-2020-0054). References Bragov, A.M., Lomunov, A.K., Lamzin, D.A., Konstantinov A.Y., 2019. Change of strength of brittle building materials under high strain and stress rates. Lobachevskii Journal of Mathematics 40, 284-291. Bragov, A.M., Lomunov, A.K., Lamzin, D.A., Konstantinov, A.Y., 2019. Dispersion correction in split-Hopkinson pressure bar: theoretical and experimental analysis. Continuum Mechanics and Thermodynamics. https://doi.org/10.1007/s00161-019-00776-0 Bragov, A.M., Petrov, Yu.V., Karihaloo, B.L, Konstantinov, A.Yu., Lamzin, D.A., Lomunov, A.K., Smirnov, I.V., 2013. Dynamic strengths and toughness of an ultra-high performance fibre reinforced concrete. Engineering Fracture Mechanics 110, 477-488. Chen, X., Wu, S., Zhou, J., 2013. Experimental and modeling study of dynamic mechanical properties of cement paste, mortar and concrete. Construction and Building Materials 47, 419-430. Frew, D.J., Forrestal, M.J., Chen, W., 2002. Pulse shaping techniques for testing brittle materials with a split Hopkinson pressure bar. Experimental Mechanic 42, 93-106. Hassan, M., Wille, K., 2017. Experimental impact analysis on ultra-high performance concrete (UHPC) for achieving stress equilibrium (SE) and constant strain rate (CSR) in Split Hopkinson pressure bar (SHPB) using pulse shaping technique. Construction and Building Materials 144, 747-757. Li, Q.M., Lu, Y.B., Meng, H., 2009. Further investigation on the dynamic compressive strength enhancement of concrete-like materials based on split Hopkinson pressure bar tests. Part II: numerical simulations. International Journal of Impact Engineering 36, 1335-1345. Li, Q.M., Meng, H., 2003. About the dynamic strength enhancement of concrete-like materials in a split Hopkinson pressure bar test. International Journal of Solids and Structures 40, 343-360. Smirnov, I.V., Lamzin, D.A., Konstantinov, A.Yu., Bragov, A.M., Lomunov, A.K., 2020. A unified experimental-theoretical approach to predict the critical stress characteristics of failure and yielding under quasi-static and dynamic loading. Engineering Fracture Mechanics 225, 106197. Thomas, R.J., Sorensen, A.D., 2017. Review of strain rate effects for UHPC in tension. Construction and Building Materials 153, 846-856. Xu, H., Wen, H.M., 2013. Semi-empirical equations for the dynamic strength enhancement of concrete-like materials. International Journal of Impact Engineering 60, 76-81. Zhang, M., Wu, H.J., Li, Q.M., Huang, F.L., 2009. Further investigation on the dynamic compressive strength enhancement of concrete-like materials based on split Hopkinson pressure bar tests. Part I: experiments. International Journal of Impact Engineering 36, 1327-1334. Zhang, Q.B., Zhao, J., 2014. A review of dynamic experimental techniques and mechanical behaviour of rock materials. Rock Mechanics and Rock Engineering, 47, 1411-1478.