Materials Science Forum Vol. 968

Abstract: The research of the deflected mode of the construction, composed of two coaxially-glued cylindrical pipes, is done. Pipes are considered as thin-walled axisymmetric shells, which are joined by adhesive layer of a certain thickness. The shearing stresses in the glue are considered to be constant over the thickness of the adhesive layer, and normal stresses are linearly dependent on the radial coordinate. The shearing stresses in the adhesive layer are considered to be proportional to the difference in the longitudinal displacements of the shell sides that are faced to the adhesive layer. Normal stresses are proportional to the difference in radial displacement of the shells. It is supposed that the change in the adhesive layer thickness under deformation does not affect the stress, that is, the linear model is considered. The problem of the joint deflected mode finding is reduced to the system of four ordinary differential equations relative to the radial and longitudinal displacements of the layers. The system is solved by the matrix method. Displacements of layers outside of the adherent area can be found by the classical theory of axisymmetric shells. Satisfaction of boundary conditions and conjugation conditions leads to a system of twenty two linear equations with twenty two unknown coefficients. The model problem is solved; the results are compared with the computation made by the finite element method. The tangential and normal stresses in the glue reach the maximum values at the edges of the adhesive line. It is shown that the proposed model describes the stressed state of the joint with high accuracy, and this joint has an influx of glue residues at the ends of the adhesive line but can not be applied in the absence of adhesive influxes. Because in this case, the tangential stresses due to the parity rule reach maximum values not on the edge, but at some distance from the edge of the line. As a result, the distribution of normal stresses at the edge of the line also substantially changes. Thus, the proposed model with certain restrictions has sufficient accuracy for engineering problems and can be used to solve design problems.

Abstract: This paper deals with the study of stochastic parameters of external loads, which are used in the tasks of determining the level of reliability of steel storage capacities. To describe the random load process, the normal law and the double exponential distribution of Gumbel were used. It was formulated the technique of transition from the study of the entire random process to the consideration of its maximums. It was obtained quantitative values of the stochastic characteristics of snow and wind loads on the territory of Ukraine, without reference to the zoning maps. A general procedure for determining the probability of failure was formulated, depending from a given characteristic maximum. This index corresponds to the basic level of load. The average intersection of this level by a random load process is equal to one. Analytical formulas are obtained to determine the scale and position of the double exponential distribution of Gumbel, which depend on the characteristic maximum, as well as formulas, which help to calculate the statistical characteristics (standard, expected value and coefficient of variation) of the random value of the load maximums. The possibility of using this approach is theoretically confirmed when the density distribution of the ordinate of a random process follows the normal law. It was proposed expressions for the parameters of the distribution maximums of the random processes, which are described by the polynomial exponent and the Weibull law.

Abstract: The article outlines the basic elements of the general theory of concrete and reinforced concrete deformation: the model of reinforced concrete elements and structures resistance to power influences; defining hypotheses necessary for the implementation of this model; criteria of the limiting state onset of the reinforced concrete elements and structures. These elements are joined together by a system of equations of a deformed solid body mechanics which is transformed into a statically distinguishable by means of additional analytical dependences.

Abstract: The article presents the results of research in the field of impact of solid bodies withmoving surfaces. Equations are obtained that allow us to determine the kinematic characteristics ofmotion of solid bodies (post-impact angular and linear speeds of the center of mass, impact impulseapplied to a solid body) in the form of a circle and an ellipse after their impact with a moving surfacefor two modes of impact — with and without slippage. The obtained equations for determining thelimiting value of friction coefficient make it possible to establish the mode of impact of solid bodieswith moving surfaces — with and without slippage. The graphical dependences of the post-impactkinematic characteristics of a solid body on the angle of incidence during impact of an elliptical solidbody with moving surfaces are presented.

Abstract: Circular cylindrical shells, application of which is widely widespread in a space-rocket technique and aircraft building, often have cutouts on the surface on structural and technological terms. The feature of the stress-strain state, when a circular hole is introduced into the shell, is the appearance of stress concentration zones, in which stress can be increased in many times. The linear static analysis often used for determination of maximal stresses in such elements of constructions does not reflect character of stresses change with increasing of the external loading. The results of Finite-Elements nonlinear static analysis of the stresses concentration caused by the hole presence depending on the size of torsion moment increasing from zero to the maximal values are presented in this article. The parametric analysis for the wide range of shells lengths and hole radii is carried out, at which different combinations the dependences of stresses concentration factor (SCF) on the value of torsion moment on all range of loading are defined. It is shown that the stresses fields, unlike the linear model of deformation, transform in the loading process. SCF obtained by taking into account the geometrical nonlinearity of deformation depends not only on the geometrical parameters of the considered sample, but also on the level of loading. There are two types of behavior of SCF dependence on the loading level and on the structure parameters. The SCF increases continuously in the first half of loading range. In the second half in case of the small holes the monotonous growth proceeds to the maximal values, and for the large holes ‒ SCF can fall at load increasing, and sometimes has the repeated areas of intensive growth in the pre-ultimate state.