A mathematical model is developed, which describes the behavior of reinforced concrete under highvelocity impact and explosion conditions within the framework of mechanics of continuous media. The problem of a model projectile penetrating into a layered target consisting of two concrete slabs separated by a sand layer and blasting of an explosive charge encased in the embedded projectile is solved in the three-dimensional formulation by the finite-element method. The effect of reinforcement on penetration and failure of reinforced-concrete slabs is studied by means of mathematical simulations.In designing protective structures of underground installations, it is necessary to estimate their resistance to high-rate dynamic loads. This problem can effectively be solved by mathematical simulation of deformation and failure of these structures subjected to an impact or explosion.The problem of the impact interaction between cylindrical metal impactors and concrete targets was solved in [1,2]. To study concrete failure, a phenomenological approach was applied, where the strength criteria are expressed in terms of invariant relations between the critical values of macrocharacteristics of the process: stresses and strains. A comparison of mathematical simulations with the results of a special experiment showed that this approach to the failure problem, used to solve static problems, can also be used to analyze concrete failure under dynamic loads.A mathematical model was developed in [3,4] to analyze the behavior of sandy soil under shock-wave loading. The processes of penetration of cylindrical and star-shaped impactors into a sandy half-space were studied by the method of computer modeling. The effect of the impactor shape on the penetration depth was revealed [4]. The problem of cylindrical impactors penetrating into structures composed of sandy soil and concrete was solved in a three-dimensional formulation [3].Much attention has been given to mathematical simulation of collisions of solid bodies with various monolithic and layered targets made of metal, ceramics, and composite materials (see, e.g., [5][6][7][8]). However, calculating the penetration of solids into reinforced-concrete slabs is still an open question. Results of experimental and theoretical studies on the impact interaction of cylindrical bodies with ogival head parts with concrete and reinforced-concrete slabs within the impact-velocity range of 100-650 m/sec and the impact-angle range of 0-40 • (the angle is counted from the normal to the target surface) can be found in [9]. In the experiments performed, the impactor diameter was smaller than the characteristic size of the reinforcing grid cell. The experimental studies show that reinforcement of a concrete target improves its bearing capacity by preventing the global failure but has little influence on the character of local failure. It follows from the experimental and theoretical results that concrete reinforcement affects the penetration of solids into typical reinforced-concrete targets only sl...
The transition to a new generation of materials operating under intense dynamic loads (impact, explosion) requires constructional materials whose strength, hardness, and fracture viscosity exceed the typical values.The fundamental advantages of ceramic materials over metals are their better performance characteristics (refractoriness, hardness, wear resistance, corrosion resistance, insulating properties, etc.) and the possibility of controlling their functional and design properties (density, strength, viscosity, etc.) over wide ranges during the production of the materials. However, under high-velocity impact, the ceramic materials based on refractory compounds are brittle and unreliable. The high-hardness ceramics contain a large number of stress concentrators (grain boundaries, cracks, pores, etc.) at which fracture nucleation is activated even in the region of elastic deformation of material. Microfractures in such materials can arise in compression under the action of deviator stresses. With an increase in the load pulse intensity, the number of microfractures in the compression stage rises sharply, which further results in a decrease in the tensile strength [1].A promising method for improving the physicomechanical properties of ceramics operating at high pressures and temperatures is to introduce an efficient metallic binder into them. The increased adhesiveness of the metal matrix and the ceramic component can be reached by producing cermet by self-propagating hightemperature synthesis under the application of pressure to the synthesis product [2,3]. Deformation compacting of the synthesis product heated by the chemical reaction opens the way to creating radically new materials with a high-hardness ceramic component. Although the physicochemical and technological principles of production of such materials are generally indicated and much has already been done, their practical implementation in each particular case requires much effort in science and technology. Analysis of the exothermicity of a number of powder mixtures based on TiC, TiB 2 , etc., showed [4] that the heat released is sufficient to produce a wide range of composites since, in the reaction mixture, the melting point of the additionally introduced filler can be reached and conditions of intense heat and mass transfer between the reagents can be created. The combination of high (up to 3000 ° C) temperatures and increased pressures in the contact zones of interfacial interaction sufficiently ensures the required adhesive properties, which is not always achieved by conventional methods for sintering powder materials. Combinations of process schemes with variation of imposed loads allow one to obtain, by selfpropagating high-temperature synthesis, both monolithic and porous cermets based on complex nonoxide ceramics. A cermet based on TiB 2 and B 4 C was obtained by this procedure.CERTAIN PROPERTIES OF TIB 2 -B 4 C CERMET Figure 1 presents the microstructure of the TiB 2 -B 4 C cermet. Against the background of the light-colored metal componen...
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