Global Journal of Science Frontier Research, A: Physics and Space Science, Volume 23 Issue 11

e) On the question of the driving force of a particle flow to the spall damage zone V. C onclusion Damageability of Metals under Impulse Loading © 2023 Global Journals 1 Year 2023 32 Frontier Research Volume XXIII Issue ersion I VXI ( A ) Science Global Journal of and increased diffusion mobility in metal matrices, which is an essential factor in the mechanism of solid-phase reactions. The authors of [38, 39] note that the active development of the mass transfer coincides with the formation of non-crystallographic shear regions with a high local deformation and an intense generation of crystal lattice defects in localization bands. The distance over which atoms can drift was shown to be estimated as 2–30 nm. At the same time, in explosive experiments, mass transfer was carried out over distances exceeding quasi-static distances by several orders of magnitude. Carbon migrates over distances of up to 50 μ m, and the process of cementite globulization under normal conditions requires many hours of exposure at high temperatures, which is seven to eight orders of magnitude higher than under impulse loads. The thermal pressure in a solid under normal conditions is determined by heating from 0 to 300 K and is = ∆ 0 , being 1.9 GPa for iron, which is compensated by the elastic pressure of the same value, here γ is the Grüneisen coefficient, с v is the heat capacity, and ΔТ is the heating temperature. In LSBs, the maximum permissible stretch, which increases the metal volume, is close to the spall strength of the material. The increase in the volume is determined by the law of conservation of mass and is ∆ 0 � = � , where D is the shock wave propagation speed. For a steel sample, the critical mass velocity is u s = 112 m/s. An increase in the volume by 2.3% corresponds to an increase in the elastic pressure ∆ = 1 0 Δ , which is equal to 3.8 GPa, here χ 0 is the isothermal compressibility. This is the driving force with which the material will strive to bring the atoms to an equilibrium state and to heal the growing discontinuity setting in motion the flow of “building” material directed toward spall damage. During high-velocity compression-tension deformation, the equilibrium system is disturbed, and the pressure, temperature, phase composition, and concentration of alloying particles periodically change. The changes occurring in the material enhance the processes of material fracture resistance, and the material strives to heal the growing damage. Under dynamic loading, the response of the material to external influences, Le Chatelier's principle, appears as Summarizing the results of the research, the following should be noted: 1. Under dynamic loading, no new deformation mechanisms were discovered that differred from quasi-static ones and were inherent only in impulse loading. 2. Impulse loading of a sample of limited sizes, which has at least two free faces, is accompanied by oscillation in the standing wave mode as a result of the interaction of counter propagating waves with each other and their reflection on the faces of the sample. 3. Under a dynamic load exceeding the spall strength, the sample is crushed, and the number of fragments is approximately equal to the ratio of the shock wave pressure to the spall strength of the material (according to [40]). 4. Under dynamic loading that is lower than the spall strength, the reaction of the material appears as the formation of localized strain bands at the nodes of the standing wave preserving the continuity of the material. 5. The formation of standing wave harmonics ( LSBs ) in the interference zones of counter propagating waves (standing wave nodes) indicates the spallation nature of localization bands, where the leading role of the process belongs to the geometry of the sample, the faces of which are sources of unloading waves. Therefore, numerous unsuccessful attempts to relate the localization process to the physicochemical characteristics of the material are understandable. 6. Localized strain bands are formed under conditions of prolonged deformation of the material in the compression-tension mode. 7. The duration of the oscillatory process of the sample after passing the shock wave is determined by the peculiarity of the standing wave to retain energy at one-fourth of the wavelength rather than to exchange energy with neighboring areas. The time of oscillation of the sample after the passage of the shock wave is several orders of magnitude higher than the initial load pulse and is limited only by dissipative processes leading to sample oscillation damping. 8. Strain localization is accompanied by a change in the phase composition inside the deformation a self-healing effect, which is aimed at compensating for changes occurring in the system. Thus, analysis of our and literature data makes it possible to explain the experimentally detected “anomalous” behavior of diffusion [25]. The self-healing effect, as a reaction of the material to impulse loading with the formation of LSBs, used a “suitable building” material in the form of a radioactive metal powder . bands. The development of physicochemical processes, such as fragmentation, dissolution of particles of the strengthening phase, globulization of pearlite, formation of spheroidal cementite in steels,