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The paper deals with the dynamics of asymmetric three-layer hemispherical shells with the discretely symmetric lightweight, rib-reinforced filler under pulsed loads. Since the distances between the ribs are much larger than the dimensions of the rib cross-sections, the theory of independent static and kinematic hypotheses for each layer is applied. In asymmetric shells, the load-bearing layers are made of different materials and have various thicknesses. The equations of motion of asymmetric three-layer spherical shells and natural boundary conditions are obtained using the Hamilton– Ostrogradsky variational principle for the Timoshenko-type shell and rod theory model. This makes it possible to develop an adequate finite element model for asymmetric three-layer shells composed of several materials and obtain numerical results on the dynamic behavior of an asymmetric three-layer elastic structure using the finite element method. The influence of physical and mechanical parameters of asymmetric layers of hemispherical shells on the stress-strain state under axisymmetric internal pulse loading is investigated. New mechanical effects are revealed. [ABSTRACT FROM AUTHOR]

A method for determining the nature of vibrations and stress–strain state of ribbed orthotropic conical shells with asymmetric layers interacting with masses under dynamic loads is developed using the theory of shells and the Tymoshenko hypotheses. The equations of vibrations of a shell formulated for the displacements of points of the midsurface are obtained using the Hamilton principle. To solve the system of equations of motion of the shell, trigonometric series in spatial coordinates and an explicit finite-difference scheme with respect to time are used. The accuracy of calculations by the finite-difference method depending on the number of time steps is estimated for a layered cylindrical shell as an example. The stress–strain state of a conical orthotropic shell with symmetric and asymmetric layers, longitudinal ribs, and masses under a short-term axisymmetric external load distributed over a portion of the shell and moving from the minor base to the major base is analyzed. [ABSTRACT FROM AUTHOR]

The stress–strain state of asymmetric three-layer cylindrical shells under nonstationary loads is considered. The sandwich structure is asymmetric due to the bearing layers that are made of different materials. The equation of motion of the asymmetric cylindrical sandwich shell with a light core reinforced with ribs is derived using independent static and kinematic hypotheses for each layer. The Tymoshenko model of the theory of shells and rods is used in the analysis of the members of the elastic structure. Numerical results on the stress–strain state and the nature of vibrations of the asymmetric elastic sandwich structure with bearing layers made of different materials are obtained using the finite-element method. The effect of the physical and mechanical parameters of layers and geometry of the shell on its stress–strain state under axisymmetric impulsive loads is studied in a wide range. [ABSTRACT FROM AUTHOR]

The stress–strain state of symmetric three-layer cylindrical shells under nonstationary loads is considered. The equation of vibrations of a shell with a light core reinforced with stiffening ribs under axisymmetric impulsive loading is derived. The members of the elastic structure are analyzed using the model of Tymoshenko's theory of shells and rods. Numerical results on the dynamics of the three-layer structure are obtained using the finite-element method. The significant effect of geometric and physical parameters of shell layers on the stress–strain state under axisymmetric internal impulsive loading is investigated. [ABSTRACT FROM AUTHOR]

During the operation of a steam generator (SG), the heat-exchange tubes (HET) and SG surface are sludged because of the inappropriate chemical and thermal conditions. The sludge accumulation can cause different defects, such as wall thickness reduction, cracks, pitting, etc. In combination with the effect of the sludge weight on the tubes and restraints for the design movement of tubes, defects change the stress–strain state of the HET substantially. To reliably evaluate the stress–strain state of the HET where sludge is accumulated and there are defects, appropriate studies were performed. The results of studying the effect of cracks on the stress–strain state and integrity of the HET are presented. [ABSTRACT FROM AUTHOR]