Creep is a slow plastic (irreversible) deformation of a product under the action of stress created in the material. This article discusses the creep of polymer products. The creep of a material is characterized by the experimental dependence of the deformation resulting from a fixed load on time.

Keywords: material deformation, elastic deformation, highly elastic deformation, polymers, viscous deformation, plastic deformation

The article deals with the transition from corrugated plates and shells to smooth structures of equivalent rigidity. An expression for the potential deformation energy of an infinitely small element of an equivalent smooth shell and formulas that establish a connection between internal forces and generalized deformations of a corrugated structure are given. A review of the formulas for the equivalent stiffness of the corrugated shell during bending, presented in the works of various authors, is carried out. In order to select the dependencies that provide the smallest error when replacing the corrugated shell with a smooth one, a numerical experiment is performed in the LIRA finite element complex. A corrugated plate hinged around the contour under the action of a uniformly distributed projective load is considered. The calculation of the structurally orthotropic construction is performed numerically by the finite difference method. It is also established that the monograph of S.G. Lekhnitsky contains an incorrect formula for the moment of inertia of a sinusoidal corrugation.

Keywords: corrugated structures, plates and shells, finite element method, finite difference method, orthotropy, equivalent stiffness

The technique of calculating the metal corrugated structures using the finite element method for an axisymmetric load is considered in the article. One-dimensional finite elements in the form of truncated cones are used. Calculations are performed using the program developed by the authors in the Matlab package. An example of calculation of a ground well rigidly clamped in the base under the action of ground pressure is given. The sinusoidal profile of the corrugation is considered. The graphs of changes in bending moments and ring forces are presented. For a smooth shell of the same thickness, the bending moment in the pinch was 30.3% higher compared to the corrugated, and the maximum value of the ring force was 15.7% higher.

Keywords: metal corrugated structures, cylindrical shell, finite element method, axisymmetric problem, soil well, shell theory, edge effect

A constructive solution of the walls of wooden houses from round logs or a profiled beam, which is installed vertically (wooden element) is considered. It is proposed to arrange two longitudinal milled grooves of a rectangular shape located in the diametral plane of the section of the log for the installation of sheet plywood keys, which makes it possible to include in the joint work adjacent contiguous elements when working on bending from the plane of the wall. The variant of the strapping device, it is proposed to use metal rolling profiles of Channel and I-sections, connected with metal tube elements (box section) mounted in the corners of the frame.

Keywords: round log, profiled beam, sheet plywood keys, tubular section elements

We obtained the solution of the optimization problem for the step-parallel beam with constant width of the cross-section. The problem was solved by minimizing the strain energy while the volume of beam is constant. The solution was made for the case of simple support at the ends and evenly distributed along the length load. We introduced the parameter α, which is the ratio of height of the average part to a height of side parts. The optimal value of α was found. At this value the stiffness of the beam is maximum at constant volume. The obtained beam of maximum stiffness is not equal strength.

Keywords: optimization, speed-prismatic beam, the strain energy, variable stiffness, minimum

We solved the problem of optimizing the gable beam by minimizing the strain energy at constant volume. The problem reduced to an integral equation for determining the optimum angle of the beam. This equation was solved numerically by the method of bisection. Integral was calculated using the method of trapezoids. Solution was made in software package Matlab. The optimum angle depends on the width of the cross section b, and the volume of the beam. It was found that with increasing of width of the cross section the optimum tilt angle decreases. Also the volume increases by increasing the width of the beam.

Keywords: optimization, gable beam, strain energy, variable rigidity, minimum volume, method of bisection

The phenomenon of buckling under the creep of concrete arches was investigated. Solution of the problem carried out by means of the finite element method. To analyze the stability we used Newton-Raphson method. It has been established that there is a long-term critical load, beyond which the growth of the deflection has not fading character. As the equation of the relationship between the creep deformation and strains we used viscoelastoplastic hereditary model of aging concrete. To determine the creep strain we used a linear approximation with respect to time. It was found that the long critical load for considered arch was in 1.44 times lower than the instant critical load.

Keywords: reinforced concrete arch, stability, creep, geometric nonlinearity, finite element method, Newton-Raphson method

Experimental and theoretical study of the models of elastic-plastic elements vehicles manufactured from alloys with shape memory effect. Dynamic tests were carried out in the area of deformation (20-30%), which allowed to achieve optimum energy absorption and return to its original position for subsequent deformation. The model proved highly efficient in terms of the one-dimensional dynamic loading, such full-scale, and allow for the absorption from 55.8 to 97.8% of the inputs, depending on the initial geometrical proportions. Evaluation of the effect of the scale factor in the simulation of elastic-plastic elements on the basis of an alloy with shape memory effect showed the possibility of transferring the results of experimental studies on a real model of the car of the future.

Keywords: model, elastic-plastic element, alloy, shape memory effect, the dynamic test, the scale factor, the car of the future

Considered concrete cylindrical body in axisymmetric formulation (plane strain condition), exposure to radiation and temperature effects. The influence of physical fields on the mechanical characteristics of the material of the body individually or in the aggregate. It is shown that the stress-strain state of the cylinder, under the joint account of the different physical fields, is very different from the stress-strain state, obtained by summing the individual results of the calculation of each factor separately, that is, the superposition principle is not respected.

Keywords: temperature field, radiation, stress-strain state of the cylinder, the change of physical and mechanical parameters of the body

The problem of temperature stresses in revetments of concrete plates taking in the account various conditions of temperature impact is considered. Contact conditions for various friction coefficient are considered. The simulation is made using finite element method in Ansys © software. The examples of exact simulations for stress fields are given for different parameters of problem

Keywords: temperature stresses, concrete plate, finite element method

Discusses the calculation of stress-strain State of glued structural sheathing to the test to determine the calibration of the test stand

Keywords: Finite elements method, Stress concentration, Skin, Test, Prediction.

The problem of optimization of thick-walled sphere loaded by internal and external pressures was solved. The essence of the method consists in the variation of the modulus of elasticity. The problem of finding the distribution of the characteristics of material in which the stress state is given, is called the inverse problem. The idea of the inverse method was proposed by academician of RAACS prof.  V.I. Andreev. The analytical dependence of modulus of elasticity from the radius at which the calculated stress on the strength theory of Mor is constant throughout the thickness of the shell was found. This shell will be equally stressed. If the strength characteristics of the material do not depend on the modulus of elasticity it will also be equiresistant. By creation of indirect heterogeneity we reduced the maximum tensions in 1.6 times. It was also shown that in the case of a centrally symmetric problem the second theory of strength is a particular case of the strength theory of Mor.

Keywords: thick-walled spherical shell, optimization, strength theory of Mor, uniform strength, equal stress

Currently actively developing direction of seismic protection, the identified using absorbing screens made in the form of sandwich structures. The present paper presents a design руктивная scheme of energy absorbing panel, which allows you to raise, if used, seismic stability of constructions.

Keywords: Dynamic loading, uprugoplastichesky deformation, deformation chart, power absorption

The paper considers arbitrarily supported arbitrarily loaded reinforced, beam with an aggregate of bimodulus of elasticity material. Formulas for determination of the tangential stresses arising in the aggregate, subject to the reinforced elements. Formulas are obtained for principal stresses occurring at an arbitrary point in the aggregate, as well as the equation for determining the point where major stresses reach extreme values. Are terms of strength as the classical theories of strength, and strength criteria applied for calculation of constructions made of bimodulus of elasticity material.

Keywords: reinforced beam, bielastic modulus, stress, normal concrete, strength criteria.

We solved the problem of optimization of thick-walled prestressed concrete cylinder loaded by internal pressure. Preliminary stresses in such a cylinder are created by wounding with tension cables on the outer surface. The idea of the method is to find the law of variation of modulus of elasticity , in which the state of stress is given . The analytical dependence of modulus of elasticity of the radius at which the tensile stress in the entire thickness of the shell does not occure was found. By creation of indirect heterogeneity we reduced the consumption of rebar by 10%.  The direct problem - determining the stress- strain state of a cylinder with a constant modulus of elasticity was also resolved.

Keywords: thick-walled prestressed concrete cylinder, optimization, inverse problem, theory of elasticity, heterogeneity