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...
INVESTIGATION OF MULTISCALE MECHANISMS OF DYNAMIC DEFORMATION AND FRACTURE OF 1565 ALUMINUM ALLOY UNDER PLANE COLLISION AND HIGH-VELOCITY PENETRATIONYu.I. Meshcheryakov, G.V. Konovalov Konovalov, A.K. Divakov, N.I. Zhigacheva & Е.P. Osokin
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...
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.
ON THE ISSUE OF ANALYTICAL DERIVATION OF STRESS STATE IN A CYLINDRICAL SHELL WITH A CIRCULAR HOLE UNDER AXIAL TENSIONS.V. Kashtanova, A.V. Rzhonsnitskiy & A.A. Gruzdkov
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...
ИССЛЕДОВАНИЕ МЕТОДОМ АКУСТИЧЕСКОГО ЗОНДИРОВАНИЯ ФИЗИКО-МЕХАНИЧЕСКИХ СВОЙСТВ ТИТАНОВОГО СПЛАВА Ti-6Al-4V, ПОЛУЧЕННОГО МЕТОДОМ ПОСЛОЙНОГО ЛАЗЕРНОГО СПЛАВЛЕНИЯА.К. Britenkov, V.М. Rodyushkin & А.V. Ilyakhinsky
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...
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...
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...
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...
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.
Institute of Problems of Mechanical Engineering12
Peter the Great St. Petersburg Polytechnic University2
Indian Institute of Technology Roorkee1
N. I. Lobachevsky State University of Nizhny Novgorod1
St Petersburg University1
Petersburg State Transport University1
St. Petersburg State Technological Institute1
Technical University of Berlin1
Indian Institute of Technology Delhi1