The article presents the results of cyclic and static mechanical tests for tension and torsion of samples grown in different areas using selective laser melting from ASP35 aluminum powder. The results of macro- and microstructural studies of the obtained additive aluminum alloy AlSi10Mg are presented. It is shown that in the deposited aluminum alloy array there are pores of various sizes and unfused particles of aluminum powder. Specimens for torsion and tensile tests are made from grown cylindrical blanks using the mechanical processing method. For cyclic tensile tests, a corset shape of the working part of the sample is chosen due to high sensitivity of the resulting AlSi10Mg alloy to stress concentration. Torsional fatigue tests are carried out using samples with a cylindrical working part. A series of cyclic tests is carried out in tension and torsion in the region of high-cycle fatigue in the soft loading mode under a symmetric stress cycle. Tensile and torsional fatigue curves are plotted for different orientations of the grown samples. A comparison is made of the anisotropy coefficient values of mechanical properties during tensile and torsional fatigue and the anisotropy coefficients during static tensile and torsion tests. It was found that during cyclic torsion the coefficient of anisotropy of properties is greater than during static tests and cyclic tensile tests. Based on the results of cyclic tensile tests, the endurance limit of the considered aluminum alloy is determined for all directions of the specimen growth. An analysis of the fracture surfaces of the samples after cyclic tensile tests is carried out. It has been shown that cyclic durability is most influenced by defects in the form of pores and unmelted particles of aluminum powder.

Plane contact problems are considered for an isotropic homogeneous elastic wedge with a thin rigid inclusion of a finite length located on its bisector. The outer faces of the wedge are subject to rigid or sliding fixation. The problems are symmetric with respect to the bisector of the wedge. The inclusion is completely coupled with the elastic medium in the contact region. A tangential force is applied to the inclusion, under the action of which it is displaced along the bisector by a given value. Using the Mellin integral transform, the contact problems are reduced to integral equations with respect to tangential contact stresses, from which the integral equations of the corresponding problems for an elastic strip can be obtained by limiting passages. Special cases also include problems with one or two inclusions in an elastic plane. The main dimensionless geometric parameter is introduced, which characterizes the relative distance of the inclusion from the wedge apex. Three methods are used to solve the integral equations. The first method consists of obtaining a closed solution based on a special approximation of the kernel symbol. The second method, regular asymptotic, involves expansion of the solution in powers of a small parameter and is effective for inclusions relatively distant from the wedge apex. The third method, singular asymptotic, involves expansion of the solution into several parts and solution of the Wiener-Hopf integral equations. A degenerate solution and a superposition of boundary layer solutions are taken. This method works for inclusions located relatively close to the wedge apex. Using the three methods, a numerical analysis is performed for different types of boundary conditions, values of the wedge angle, Poisson's ratio, and the main dimensionless parameter.

One of the first two-level physically oriented models intended to describe plastic deformation was the rigid-plastic model of J.I. Taylor, the mathematical justification of which was subsequently presented in the works of J. Bishop and R. Hill. Various versions of models based on the main provisions of these pioneering works are usually called in the literature models of the Taylor–Bishop–Hill (TBH) type. Despite the prevalence of TBH-type models, they have disadvantages (the presence of a connection is a condition of incompressibility, the uncertainty of choosing a set of five slip systems when the condition of activation of six or more systems is met). Taking into account elastic deformations, introduced in the later model of T.G. Lin, made it possible to overcome the disadvantage associated with the presence of a constraint. At the same time, it became possible to realize elastic-plastic deformations when less than five slip systems are activated. However, the most important disadvantage is the uncertainty in choosing a set of active slip systems – remains. It should be emphasized that the limitation of the number of slip systems to five when the representing point in the stress space hits a vertex of a higher order than the fifth is due only to the procedure for solving the velocities (or increments) of shears and stresses. There is no physical justification for such a limitation. In this regard, since the 70s of the twentieth century, two-level elastoviscoplastic (i.e., sensitive to strain rate) models have become most widespread. It was shown that when the velocity sensitivity parameter tends to zero, the resulting solution converges to the solution of the elastoplastic model. However, in this case, the system of equations of the constitutive model becomes rigid, which leads to the need to use implicit integration schemes and a significant decrease in computational efficiency. Taking this circumstance into account, numerous attempts have been made to get rid of this most important disadvantage of TBH-type models, however, the options known to the authors are reduced to various mathematical procedures that do not have proper physical justification. In this work, we propose a version of a physically based elastic-plastic model that uses the basic provisions of TBH-type models, but is free from the disadvantages noted above. When more than 5 slip systems are simultaneously activated, they are all considered “equal” for the implementation of plastic deformation by shear. An iterative procedure is proposed to determine the rates (increments) of shears for all slip systems that are potentially active at the moment of deformation under consideration.

The paper studies the dependence of the dynamic characteristics of an electro-viscoelastic system, which is a piecewise homogeneous body consisting of elastic, viscoelastic, electroelastic (piezoelectric) elements, as well as external passive electrical circuits attached to the electroded surfaces of piezoelectric elements, on the parameters determining its geometric configuration (dimensions and location of viscoelastic and piezoelectric elements, forming the system, in relation to structure and each other). In these systems, two methods of energy dissipation are used to reduce vibration: internal friction in viscoelastic materials and the conversion of mechanical vibration energy into electrical energy which is then dissipated in electrical circuits. Resistive (R) and resonant (RL) circuits are considered as examples of external electrical circuits. The study was conducted based on a numerical solution to the natural vibration problem for a thin-walled, spatial structure having the form of a semi-cylindrical shell. All possible geometrical configurations for the arrangement of viscoelastic and piezoelectric components were considered. There were found designs that could provide optimal damping properties within a specific frequency range, either via internal friction or by converting vibration energy using a piezoelectric component. As a result of a series of computational experiments, we obtained quantitative estimates demonstrating how the damping properties of the system change when each of the considered vibration energy dissipation mechanisms is used separately or jointly. The obtained quantitative estimates of changes in the dissipative properties of the shell show, in which cases both energy dissipation mechanisms lead to an increase in the damping characteristics of electro-viscoelastic systems, and in which cases they lead to a decrease.