PSI - Issue 13

Bragov A.M. et al. / Procedia Structural Integrity 13 (2018) 1811–1816 Author name / Structural Integrity Procedia 00 (2018) 000–000

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b) Fig.5. The dependence of the dynamic fracture toughness on time to failure (a) and on the loading rate (b)

4. Conclusions The characteristics of the tested steel under tension (yield strength, ultimate plasticity characteristics) are practically independent of the strain rate (in the investigated range of its change). The effect of the test temperature on mechanical properties during tension is quite significant. When tension specimens with an annular notch, the change in the amplitude of the loading wave (the speed of the striker) basically affects only the "life" of the specimen, i.e. for a time before the onset of failure, whereas the magnitude of the destructive forces depends from the amplitude of the loading wave rather weakly. The effect of "cold-brittle" steel (decrease in toughness) is noticeable at temperatures below -50 0 C. For the fracture toughness test the specimens shall have a pre-grown fatigue crack (preferably) or a different curvature at the top of the cutout. To reduce the scatter of the resulting ultimate strength and deformation characteristics, it is necessary to control the cutting of the specimens relative to the rolling direction. Acknowledgements Experimental studies were carried out within the framework of the Ministry of Education and Science of the Russian Federation, grant No. 9.6109.2017/6.7. Theoretical analysis of the results from the standpoint of the criterion of incubation time was carried out with financial support under a grant from the Government of the Russian Federation (No. 14.Y26.31.0031). Y. Petrov acknowledges support from the Russian Science Foundation (17-11-01053) for the creation of sections 2.3 and 3.3. References Bragov, A.M., Lomunov, A.K., 1995a, Use the Kolsky method for dynamic testing of structural materials. Problems of Strength and Plasticity Journal 51, 127-137. [in Russian] Bragov, A.M., Lomunov, A.K., 1995b, Methodological aspects of studying dynamic material properties using the Kolsky method. Int. Journal of Impact Engineering 16(2), 321-330. Bragov, A.M., Lomunov, A.K., Sergeichev, I.V., 2001, Modification of the Kolsky method for studying properties of low-density materials under high-velocity cyclic strain. Journal of Applied Mechanics and Technical Physics 42(6) 1090-1094. Bragov, A., Konstantinov, A., Lomunov, A., Sergeichev, I., Fedulov, B., 2009, Experimental and numerical analysis of high strain rate response of Ti-6Al-4V titanium alloy. Journal de Physique IV. 1465-1470. Kogut, N.S., 1986, Crack resistance of structural materials. Lvov. 160. [in Russian] Nicholas, T., 1981, Tensile testing of materials at high rates of strain. Experimental Mechanics 21(5) 177-195. Petrov, Y.V., Utkin, A.A., 1989, Dependence of dynamic strength on loading rate. Sov. Mater. Science 25(2), 153-156. Petrov, Y.V., Morozov, N.F., 1994, On the modeling of fracture of brittle solids. ASME Journal of Applied Mechanics 61, 710-712. Savruk, M.P., 1988, Coefficients of stress intensity in bodies with cracks. In: Mechanics of failure and strength of materials. Vol.2. Kiev. 620. [in Russian]