This article discusses the problem of ensuring strength and minimum mass in the design of products manufactured using additive technologies. The authors investigated the possibility of using topological optimization in computer-aided design systems to create an optimized model with the necessary strength at a minimum weight. As part of the work, the topological optimization of the bracket, the production of its samples by additive manufacturing methods and strength tests were carried out. The optimal values were found via finite element analysis using the SolidWorks and ANSYS software. The calculation results show that the optimized model retains about 20% of the original mass and has the necessary mechanical characteristics. In particular, the excess safety margin is reduced by 2.5 times, which is acceptable for this bracket. The subsequent verification of the models is carried out through destruction tests of the products manufactured using additive technologies, i.e. the method of filament deposition and stereolithography. To account for the anisotropy of the material, a series of samples oriented at different angles to the direction of construction was made. The tests were carried out on a test bench for simultaneous biaxial stretching, which corresponds to the design loads on the bracket. An increase in the tensile load on the sample was carried out before its destruction. In the course of the work, the presence of anisotropy of mechanical properties was revealed, and optimization results in various software packages were studied. The results of strength tests allow us to draw two conclusions. Firstly, due to the anisotropy of the material, the strength properties significantly depend on the orientation of the bracket during additive manufacturing. Secondly, the bracket, optimized by means of the SolidWorks software package, generally showed the best strength properties for various orientations during manufacturing. Also, which is quite expected, the samples obtained by stereolithography showed less anisotropy than the samples obtained by the method of filament deposition. In conclusion, it is noted that the use of additive technologies to create optimized forms requires considering printing technologies and anisotropy of properties, as well as the choice of appropriate software.

The problem of large deflections of a flat arch in its plane (or an infinitely long panel) loaded with transverse loads is considered. A variational approach has been applied to solve it. The resolving nonlinear equations are reduced to finding the deflection and longitudinal force, which is considered constant along the length of the arch due to its flatness. An approximate solution method is proposed by decomposing the displacements into a Fourier series. The peculiarity of the approach used is that in order to pass the limit points, it is not necessary to use special algorithms such as the continuation method by parameter. It also allows you to trace the process of supercritical deformation of the arch. The proposed approach allows us to consider problems for arches of variable thicknesses, located on elastic supports, on an elastic base with a variable bed coefficient and various loads. Therefore, it is also convenient in problems of finding, for example, the optimal thickness distribution under restrictions on critical loads, on rigidity stiffness and on maximum compression or tension stresses. The results of numerical calculations are presented. The convergence is studied of the solution depending on the number of terms of the series, into which the desired deflection decomposes. A good agreement with the known analytical results is obtained earlier by solving the equilibrium equations of the arch element and panel in the case of simple types of loading. At the same time, even in more complex cases of loading and supercritical bending of an arch without an elastic base, the results are obtained when holding three, four and five members of the Fourier series, the maximum deflections and critical loads differed by no more than 2.5%. On the basis of numerical experiments, the features of the arch behavior caused by the rearrangement of geometry during loading are revealed. The processes of stability loss of the arch and its supercritical behavior are investigated. The effect of symmetric deformation in the case of kinematic loading is found, namely, it is revealed that at a certain value of the concentrated force, an infinite number of equilibrium forms are possible. Arches on an elastic base, as well as with variable thickness are considered (the results are presented in the form of load–displacement diagrams and in the form of pictures of deformed arch shapes). An interesting effect has been revealed based on numerical experiments. It turned out that the increase in thickness when moving away from the supports does not change the nature of the load–displacement diagram, i.e., with some load, a slap occurs. On the contrary, a decrease in thickness when moving away from the supports leads to a flattening of the diagram, and after a certain thickness value in the center, its further decrease leads to the fact that the arch does not occur.

The paper considers the process of curing a photopolymer material. The effect of light on a photopolymer material triggers a reaction that leads to the conversion of polymer chains, which leads to the release of heat and an increase of temperature, solidification or an increase of stiffness of the material, and is also accompanied by a volumetric shrinkage. Such processes cause the distortion of the initial shape of the material. With nonuniform irradiation of the material, the processes are initiated with different intensities and a certain delay causing residual stresses. Stereolithography technology has become widespread in industry, in which the material is irradiated in certain areas, the so-called masks, after which the uncured material is removed. Modern photopolymer 3d printers are focused on this effect, which cures the material in layers with various masks. In 3D printing, the curing of the upper layer is accompanied by a higher shrinkage relative to the lower one, which by this time has a higher degree of curing leading to residual stresses. Thus, each new layer in a produced part initiates a gradual accumulation of residual stresses. As a result, there is a distortion of the originally planned shape of the product and a loss of strength characteristics. Residual stresses realized during the printing process can exceed the strength of the material, which often leads to a rapid increase in cracks and damage of the printed structure. This study proposes a model of a photopolymer material and an algorithm for modeling curing. It considers the process of stereolithography based on the action of a movable laser. A comparison with the experiment is given.

This paper proposes mathematical models of mechanical systems "pipeline - pressure sensor" designed to control the pressure of the working medium in the combustion chambers of engines. In such systems, to mitigate the impact of vibration accelerations and high temperatures, the sensor is connected to the engine using a pipeline and is located at some distance from it. The movement of the working medium is described by linear models of fluid and gas mechanics. To describe the dynamics of an elastic sensitive element, linear models of the mechanics of a solid deformable body are used. Based on linear differential equations with partial derivatives, mathematical formulations of problems are proposed that correspond to three-dimensional models of pressure measurement systems in gas-liquid media for some pipeline cross-sectional shapes, namely, for a pipeline with a rectangular cross-section, with a section in the form of a sector and in the form of a ring. By introducing integral characteristics, the solution of problems is reduced to studying one-dimensional models. Equations have been obtained that make it possible to determine the pressure of the working medium in the combustion chamber at each moment of time by the value of deformation of the sensitive element of the sensor. Analytical and numerical-analytical methods for solving the corresponding initial-boundary value problems for systems of differential equations are proposed. In the analytical approach, the solution of the problem is reduced to solving a differential equation with a deviating argument. The numerical-analytical study of the problem is based on the application of the Galerkin method. Also, a numerical experiment was carried out and examples of calculating the deformation of the sensitive element of the sensor in the case of rigid fastening when specifying specific values of the mechanical parameters of the system are presented, also during setting the law of change in the excess pressure of the working medium in the engine.

The process of deformation of an underwater two-layer gas pipeline during the explosion of a nearby octogen charge is simulated. For modeling, a specially developed proprietary software package is used to solve three-dimensional dynamic problems of interaction of elastoplastic structures with compressible media, based on a single Godunov scheme of increased accuracy for calculating the joint motion of gas, liquid, and elastoplastic media. The package uses an Eulerian-Lagrangian approach with explicit identification of moving contact surfaces between different media. For each environment, three types of computational grids are used. These are Lagrangian surface meshes in the form of a continuous set of triangles for specifying the initial geometry of bodies and accompanying them during the calculation process, as well as two types of three-dimensional volumetric meshes automatically generated during the calculation process. The charge, which has a spherical shape, is initiated at its center. To describe the process of propagation of steady-state detonation, the hydrodynamic theory of detonation is used. Shock waves generated during an explosion in the surrounding liquid interact with a fragment of a two-layer pipeline and a solid bottom. Wave processes are analyzed both in the steel pipe and in the concrete shell that weighs it down. Loads on the pipeline are estimated depending on the distance to the charge and the position of the pipeline relative to the bottom. The possible destruction of both steel and concrete weight shells in areas of tensile deformations that are formed in places of the maximum bending of the pipeline is shown. It is shown that the proximity of the bottom can significantly enhance the impact of explosive loading due to the action of shock waves reflected from the bottom.