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The computer simulation of the propagation of a blast wave generated by various explosives is carried out. The simulation used numerical methods to solve dynamic problems in the mechanics of a deformable solid, which allow one to investigate the development of waves during the explosion of charges of various shapes at different speeds of detonation of explosives and various conditions of placement of charges in the hole. The novelty of the research is related to analysis of conditions for the formation of a tensile pulse, which determines the opening of natural and induced defects in a zone remote from the explosion (from 20 to 100 radii of charge), which is known as the zone of explosive pre-fracture. [ABSTRACT FROM AUTHOR]

The paper presents the results of numerical simulation of the output optical signals of mechanoluminescent shock sensors. Such sensors operate on the principle of direct conversion of mechanical impact energy into optical radiation energy. The sensing element of such a sensor is a thin layer of phosphor enclosed between two transparent flexible polymer films. The mathematical model of the sensor is based on the process of excitation of the glow centers (activator atoms) in a strong electric field of a moving dislocation. The stress-strain state of the film sensing element under quasi-static uniaxial loading under the action of a single pressure pulse is considered. The analysis of constitutive equations for elasto-plastic deformations and the basic equations of the dynamic theory of dislocations. To calculate the deformation of the sensing element, a microscopic model of an isotropic elastic-plastic medium with hardening is used, according to which the plastic deformation is considered as a result of the movement and multiplication of dislocations, and the hardening is as a result of their partial locking due to the increased density. [ABSTRACT FROM AUTHOR]

A numerical 3D model of friction at mesoscale of the contact patch between steel samples and composite steel samples with carbon nanoinclusions has been developed based on the movable cellular automaton method. The response function of automata simulating steel corresponds to an elastic-plastic body with linear hardening, and the function for simulating carbon corresponds to an elastic-plastic body with bilinear hardening. Von Mises criterion is used for breaking bonds between the automata, and the criterion based on plastic heat is used for coupling the automata. The values of basic parameters of the model, as well as the loading conditions, that allow the formation of the characteristic quasi-liquid layer in the friction zone are determined. It was shown that the presence of carbon nanoinclusions in the contact region leads to decreasing of the coefficient of friction, lower values of stress, and higher shear strain in the friction zone. [ABSTRACT FROM AUTHOR]

The process of fatigue fracture of carbon fibres reinforced plastic under compressive loads is considered from the standpoint of the theory of reaction rates. Numerical simulation is based on rheological structural models of the material, which reproduce thermodynamic processes of local plastic deformation and failure occurring in time. The prediction of longevity of composite materials under compressive loads is similar to the solution of the problem for metal alloys under tensile loads when temperature and stresses are arbitrary functions of time. [ABSTRACT FROM AUTHOR]

In many fracture problems, fragmentation is essentially a probabilistic process, which is determined by the stochastic nature of the distribution of inhomogeneities of the internal structure of material. The probabilistic approach is described, which allows us to model structural heterogeneities of the material in a simple form, practically without any complication of the model and additional experiments. Using experimental data and numerical simulation results, it is shown that the introduction of only one additional parameter (dispersion of the strength properties distribution) into the material model makes it possible to give a probabilistic character to the crack formation process at any scale level, which corresponds to theoretical concepts and experimental data. Distribution of materials strength characteristics (according to the selected distribution law) in the cells of the computational domain is used for initial heterogeneities and materials structure defects modeling. It is shown that the number and size of the "petals" at the penetration of thin barriers depend of the speed of the projectile and the strength characteristics of the barrier. [ABSTRACT FROM AUTHOR]

The study represents the mathematical model of distorting and destruction of ordinary brick and masonry when subjected to shock-wave loadings. The research of the impact dynamic strength of the masonry's two fragments to the steel drop-weight of 1-2 m, weighing 197-1000 kg, was conducted by using the method of the computer modelling. [ABSTRACT FROM AUTHOR]

This research is aimed at studying the method for improving blast resistance of buildings and structures by using yielding supports. The paper reports the data on dynamic analysis of reinforced concrete elements subjected to compression and bending on yielding supports under the condition of elasto-plastic stress-strain state performed in ANSYS software package. Algorithms and techniques for dynamic amplification factor calculation for reinforced concrete elements subjected to compression and bending are presented. The paper provides load diagrams of dynamic amplification factors with the account of yielding capacity of supports for subsequent dynamic analysis of structures for equivalent static load. [ABSTRACT FROM AUTHOR]

To create protective elements, information is needed on the resistance of various combinations of metal, ceramic, and heterogeneous plates, including layered ones, both in contact and with spacing. In addition, an intensive process is underway to create complex materials such as cermet composites. In this work, for verification of the code, numerical calculations of the breakdown of both monolithic and layered steel barriers by a striker with an ogival nose are performed. A series of 2D and 3D calculations for modeling the processes of penetrating heterogeneous barriers has been performed. It is shown that the resistance of heterogeneous barriers to penetration by a rigid striker is approximately the same, whereas the impact of a deformable striker on heterogeneous barriers shows that the resistance of layered barriers is lower compared to a monolithic barrier, and spacing of layers reduces the resistance of the barrier. [ABSTRACT FROM AUTHOR]

A two-dimensional and three-dimensional non-stationary problem of the interaction of a homogeneous impactor and a heterogeneous structure made of steel and ceramics and placed in a Kevlar pocket is considered. The model of the human body is a plate of gelatine with cylindrical inserts-imitators of human bones. The results of numerical simulation using different approaches for describing heterogeneous media are compared. On the basis of direct numerical simulation, it is shown that the gradient armor plate (steel + B4C) has the best weight and size parameters. [ABSTRACT FROM AUTHOR]

The paper is devoted to theoretical study of the longitudinal shear (mode II) crack unstable growth dynamics in brittle materials. We considered two main regimes of the dynamic propagation of the crack (sub-Rayleigh and supershear) and their implementation conditions. The research was carried out by computer simulation with the Movable Cellular Automaton method, using the generalized kinetic fracture model, which takes into account the finite duration of local fracture (fracture incubation time). It is shown that the fracture incubation time is a key parameter, which determines the transition conditions of the shear crack growth process from the sub-Rayleigh regime to supershear. [ABSTRACT FROM AUTHOR]

The questions of application of the LS-DYNA finite element analysis package for describing the interaction of a spherical projectile and a massive metal obstacle are considered. Based on a comparison of the results of numerical simulation with experimental data, a qualitative possibility has been shown to determine the magnitude of the dynamic hardness of the obstacle material.A simulation of the collision of a spherical impactor and a massive metal barrier shaped as a cube is performed. Data are obtained on the penetration of the striker into the barrier.Using the simulation curve, the values of the dynamic hardness of the obstacle were restored and a comparison was made with their experimental values. The qualitative correspondence is shown. [ABSTRACT FROM AUTHOR]

The paper presents results of applying approach to simulation of contact surfaces fracture under high velocity interaction of solid bodies. The algorithm of erosion -the algorithm of elements removing, of new surface building and of mass distribution after elements fracture at contact boundaries is consider. The results of coordinated experimental and numerical studies of fracture of materials under impact are given. Authors own finite element computer software program EFES, allowing to simulate a three-dimensional setting behavior of complex structures under dynamic loads, has been used for the calculations. [ABSTRACT FROM AUTHOR]