The concept of a vertical barrier embedded in soil to protect from seismic waves of the Rayleigh type is discussed. Horizontal barriers are also analyzed. The principle idea for such a barrier is to reflect and scatter energy of an oncoming wave by the barrier, thus decreasing the amplitude of surface vibrations beyond the barrier. Numerical FE simulations of a plane model are presented and discussed.

Mechanical wear resistance of the α- and β- Ga2O3 polymorphs is experimentally studied. We report about tribological cyclic tests of these wide-band-gap semiconductor crystals. To the best of our knowledge, this is the first attempt at considering these crystals as protective coatings. The crystalline layers were deposited on sapphire substrates by vapour-phase epitaxy. This method allows applying coatings on large areas and surfaces of complex shapes, including the surfaces of a number of metals. It...

The paper presents comparative numerical analysis of two ceramic materials subjected to impact loading. ZrO2(Y2O3) and Al2O3 ceramics are studied. The main objective of the work is to study influence of various material parameters on ballistic performance of ceramic materials and on characteristics of the dynamic fragmentation process. The applied numerical scheme is based on finite element method and incubation time fracture criterion. Results on fracture surface area, residual impactor velocity, fragment size distribution are...

A theoretical model of axial misfit stress relaxation in core-shell nanowires with hexagonal cross section of the core through the nucleation of prismatic dislocation loops is suggested. Different nucleation sites of the loops in core-shell nanowires are considered. The energy change caused by the loop nucleation is calculated. The critical condition for the onset of the loops is given and analyzed in detail. The most favorable sites in nanowires and the optimal loop shape are...

High strength 1565 aluminum alloy was tested within impact velocity range of 250- 750 m/s in two schemes of shock loading: (i) under uniaxial strain conditions and (ii) in highvelocity penetration. The combination of load regimes allows the different stages of multiscale structure formation to be retraced. The intensity of macro-meso momentum exchange is found to be responsible for both resistance to spallation and high-velocity penetration. The overall impact velocity region is found to be...

In the present work, the pair interaction of coaxial circular prismatic dislocation loops (PDLs) arbitrary placed in elastic solids with free spherical surfaces is considered. The analytical solutions for the pair interaction energies of PDLs in an elastic sphere, an elastic medium with a spherical pore and a spherical layer are given in the form of double power series and illustrated by energy maps built in the space of the normalized PDL radii and axial...

This study is concerned with the modeling of plate buckling induced by a chemical reaction and is inspired by the observation that buckling may be a mechanism of stress relaxation in Si-based anodes in Li-ion batteries. A chemical reaction is localized at a sharp interface and accompanied by transformation strains, which produce internal stresses. If external supports restrict the deformation of the plate, buckling may occur. At the same time, mechanical stresses affect the kinetics...

Для проведения расчётов в процессе разработки низкочастотных гидроакустических преобразователей необходимы данные о физико-механических свойствах конструкционных материалов, таких как плотность, модуль Юнга, коэффициент Пуассона, предел прочности. Для изготовления излучающей оболочки (корпуса) преобразователя используется специфический материал, получаемый методом послойного лазерного сплавления. Параметры материала, изготовленного таким методом, зачастую существенно отличаются от табличных данных. В работе приведены результаты исследований физико-механических свойств титанового сплава Ti-6Al-4V, полученного методом послойного лазерного сплавления. Исследования проведены методом упругих волн и разрушающего воздействия. Результаты исследований...

We suggest a model, which describes the effect of grain boundary relaxation on the annealing-induced hardening in ultrafine-grained metals. Within the model, grain boundary relaxation during annealing is accompanied by a decrease in the number of grain boundary dislocation sources. The exhaustion of easily activated grain boundary dislocation sources results in the activation of harder grain boundary dislocation sources and/or repetitive action of the same dislocation sources. This gives rise to an increase in the...

The paper briefly reviews progress in numerical simulations of dynamic crack propagation and fracture of initially intact media and presents examples of simulations utilizing finite element method with embedded dynamic fracture criterion based on the concept of incubation time of brittle fracture introduced by Petrov and Morozov. The examples include dynamic fracture initiation, propagation arrest, and evolution of fracture zones in initially intact media. It is demonstrated that this approach is capable to give an...

We consider an elastic inclusion in a cylinder with isotropic materials properties. The inclusion possesses a multi-step dependence of the dilatational eigenstrain along the cylinder axis. Basing on the solution for the trace of the stress tensor of the dilatational inclusion with sharp boundaries (single-step inclusion) the stored elastic energy of the multi-step inclusion is determined and analyzed. Then, the found analytical solution for the inclusion energy is used to investigate the energy properties of...

The stress field in the cylindrical shell with the circular hole is considered. Thoroughly analyzing previous works we concluded that up to the present there are no explicit formulae useful for applications despite numerous works on this subject. Moreover, the classical analytical approach lacks a rigorous mathematical foundation. Its applicability is limited to cases that slightly differ from the plane Kirsch problem. The numerical results of various researches show a significant discrepancy. This paper proposes...

Numerical study of crack opening in the solid material of rock formation is presentedin this article. Initially introduced straight-line crack is widened by increasing internal pressure. The crack shape evolution resembles hydraulic fracturing and is considered as a transient process. Commercial code LS-DYNA was employed to obtain solutions by three types of descriptions, they are compared to the solution obtained in Eulerian description by a program based on the finite-volume method and written in Python...

In order to identify the successive stages of developing the hierarchy of multiscale mechanisms of dynamic straining, the shock-induced mesostructure formation is studied in combined experiments. Shock tests of two kinds of aluminum alloy, 1561 and 1565 alloys were conducted in parallel in two regimes of loading: (i) under uniaxial strain conditions and (ii) in high velocity penetration. Combination of loading regimes allows the correlation in formation of multiscale structure depending on strain rate and...

Under the assumption of structural softening of plastic deformation in metals, a solution of the system of equations for the ensemble of dislocations is obtained describing a running front for the dislocation density (soliton). Such dislocation charge is able to destroy deformation barriers and cause an athermal mechanism of the instability of the lowtemperature plastic deformation.

In this article, the solution to the elasticity boundary-value problem for an infinitesimally thin dilatational disk (ITDD) embedded in an elastically isotropic half-space is presented. The plane of the disk is parallel to the free surface. To solve the boundary value problem, the method of virtual defects is used. The image (mirror) ITDD and radial Somigliana dislocation loops (RSDLs), distributed continuously over the free surface coaxially with the ITDD, are chosen as virtual defects. The...

The mechanism of localization of low-temperature plastic deformation is investigated within the framework of the thermal activation model. The localization mechanism is considered as a result of the autowave character of the stationary solution of a system of equations that describes both the processes of thermal conductivity and plastic deformation. It is established that the stationary solution of the initial problem is given by the wave fronts of switching waves of temperature and plastic deformation....

The ballistic behaviour of a bi-layer ceramic-metal target against steel projectile with varying layer thicknesses has been investigated using a three-dimensional finite element model. The bi-layer target was made of alumina 99.5 % ceramic front layer and aluminium 2024-T3 metallic back layer with an areal dimension of 100×100 mm and the thickness of both layers were varied, with the total thickness of the composite being kept as 10 mm and 20 mm. A steel 4340...

An attempt is made to find the relationship between the mechanical properties of the material in microvolumes and the properties of the material under load. A fractographic analysis of the surface of a fatigue fracture of a railway rail with an internal transverse crack is presented. The relationship of fractographic features with the structure of the material is discussed.

An asymptotic representation is obtained at large times for the thermal wavefront propagating in a one-dimensional harmonic crystal. The propagation of thermal waves from a localized thermal perturbation and the transition zone between regions with different temperatures is considered. An explicit solution is given for a number of the simplest forms of the initial temperature distribution. It is shown that during the wave evolution, the wavefront smoothes, e.g., for a power-law dependence its degree increases...

Surface growth of solids includes a wide variety of processes starting from additive manufacturing technologies and ending with plenty of biological problems. Model of surface growth based on the expression of the configurational force, derived from fundamental laws and entropy inequality, is offered in the present paper. A new expression for the configurational force called surface growth force, which controls growth and resorption, is used. Analysis of the applicability of the developed model was carried...

A 3D finite element model has been developed for studying the ballistic behaviour of bi-layer ceramic-metal target plates under the impact loads induced by the projectiles of different diameter to length ratios. The bi-layer target constituted of alumina 95, as front layer, backed by aluminium alloy 2024-T3 layer, has been impacted by steel 4340 blunt and ogival nosed projectiles of diameter to length ratios, 0.5 and 1.1. The constitutive behaviour of ceramic was modelled using...

The mode of the serrated deformation is investigated mathematically in framework of the thermoactivation model of unstable plastic deformation in metals at low temperatures. The obtained solutions in the framework of known models, however, do not fully correspond to experimental situation, as the stress oscillations in reality are usually irregular and inhomogeneous. By this reason, additionally, the elastic correlations of neighboring deformation zones were taken into account in the model. Numerical analysis model showed that...