Diffusion crushing of graphite in integrated cast iron processing

Purpose. It is necessary to investigate the possibility of crushing graphite inclusions in cast irons. The aim of the work was to study structural changes in graphite under explosive action followed by thermal cycling treatment of gray cast iron. Methods. Gray cast irons were subjected to explosive action (pressure is 90 GPa, the deformation rate is 100 s-1, the time is 10-6...10-7 s). Then the cast irons were subjected to thermal cycling: 950 °C, holding for 20 min, cooling with a furnace; 5 cycles. Metalographic ("Neophot-21"), micro-X-ray spectral ("Nanolab-7"), X-ray diffraction (DRON-2.0) research methods were used. Results. The features of diffusion crushing of graphite in cast irons with different types of metal matrix (ferritic, austenitic) and graphite shape (lamellar, spherical) have been studied. The features of structural changes in the cast iron matrix under explosive action, which determine the conditions for the transformation of graphite during subsequent thermal cycling, are discussed. It is shown that this process of diffusional crushing of graphite can be accompanied by local melting, which leads to the formation of regularly distributed dispersed particles of graphite. Scientific novelty. From the point of view of physical mesomechanics of plastic deformation, the processes of structural changes in the metal matrix of cast irons are considered. It is shown that nonequilibrium defect substructures of the cast iron matrix obtained during the explosion determine the features of diffusion crushing of graphite inclusions during subsequent thermal cycling. The conditions for diffusion crushing of graphite with reflow and in the solid-phase state have been established. Practical significance. It has been established that the complex processing of “explosive loading + thermal cycling” promotes crushing of coarse graphite inclusions, which is favorable for the mechanical and operational properties of cast irons. The use of the results obtained will make it possible to develop technologies for complex processing with regulated parameters of graphite inclusions, which will lead to an expansion of the field of application of gray cast irons. Keywords: cast iron; shock wave treatment; graphite; thermal cycling; stress relaxation

Improvement of the calculation methodology for covering constructions of the covered field fortifications to ensure the survivability of troops in a modern armed conflict

The task of improvement of the calculation methodology for covering constructions of the covered field fortifications against shell-hole, penetration, ricochet and high-explosive action is solved to ensure the survivability of troops in a modern armed conflict. An analysis of the 2014-2018 anti-terrorist operation and the ongoing Joint Forces operation proves that artillery, mortar and aircraft high-destructive munitions are currently the main means of firing the enemy. Under such conditions, the survival of our troops directly depends on their effective shelter in covered field fortifications. An important element of the arrangement of such fortifications is the calculation of the structures of their covering against penetration, shell-holing, ricocheting and high-explosive action, which are performed to determine the structure of the covering, its material and thickness. The novelty of the improved technique, unlike the existing ones, is that the calculations of the covering structures take into account the shape of the warhead of artillery, mortar and aircraft ammunition, the angle of encounter and the final speed of these munitions at the moment of their impact on the covered fortification and the pliability of the covering material. Here are given the examples of calculation for the closed field fortifications structures against penetration of the warhead into the covering material, cases of punching the covering material enclosed with brittle material, ricochet of the warhead from the covering and destruction of the covering as a result of high explosive action. The obtained results will be used to calculate the protective structures of long-term fortifications for command and control centres and field hospitals.

EXTINGUISHING FIRES OF ALCOHOLS AND THEIR MIXTURES

In order to increase the efficiency and the rate of extinction, it was proposed to use extinguishant aerosols to extinguish. Extinguishant aerosols are more comfortable in operation and cheap compared to gas, foam and water fire extinguishing. As for the phlegmative concentrations, it is apparent that all of these substances have different values ​​of phlegmative concentration. The lowest levels of phlegmatic concentration are for extinguishing aerosols, which, due to the developed surface, effectively interrupt chain reactions and perform explosive action. The work substantiates that quenching of alcohols with volumetric extinguishants is of interest from the standpoint of efficiency, cost, speed and the possibility of explosive depletion of alcohol-air mixtures, and the creation of new effective gas-aerosol mixtures is an urgent issue to be addressed. The following main results were obtained in the work, namely, the process of extinguishing polar liquids is not perfect at present and in almost all cases, the polar fuel-emitting native suffers quality losses. In addition, the amount of foaming agent is much higher than the amount required for alcohols, and the cost of this type of foaming agent is several times higher than the cost of a general purpose foaming agent. In addition, extinguishing with extinguishants of volumetric action is much more effective than foam quenching as the extinguishing agent of the volume action extinguishes 3 D fires. For further increase of extinguishing efficiency and reduction of liquid losses during extinguishing, it is relevant to further study gas-aerosol mixtures in their various combinations.