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The effect of distributed end-face and local axisymmetric operational non-stationary loads on sandwich cylindrical shell elements of rocket bodies has been studied. The action of the engine is characterized by longitudinal forces that have time-varying frequency and amplitude and are applied to the end of the shell. Additionally, we have simulated local axisymmetric external impulsive loads applied along the directrix of the cylindrical shell to the place of ribs and between them to imitate an explosion of an elongated cumulative instantaneous charge. Given the different material properties of the face layers, light core, and reinforcing ribs, it is advisable to employ the finite-element method. By finite-element modeling of the dynamics of the structure under operational loads, this research enables thoroughly investigating the effect of the light core and facilitates choosing the optimal locations for applying local axisymmetric impulsive loads. The numerical results obtained from real object simulations, based on the developed methodology, allow us to give recommendations for determining the optimal amount of cumulative charge necessary for separating the rocket's spent stage while maintaining its prescribed trajectory. [ABSTRACT FROM AUTHOR]

The effect of distributed and localized axisymmetric impulsive loads on three-layer cylindrical shell elements of rocket airframes is studied. Localized axisymmetric impulsive external loads applied along the directrix of a cylindrical shell simulate an explosion of a superquick-action elongated shaped charge. Finite-element modeling of transient processes in such elements under such loads allows correct selection of the physical and mechanical parameters of cylindrical rocket airframes. A significant effect of the behavior of dynamic loads on the transient processes in three-layer cylindrical elements is demonstrated. [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]

A technique to study the transient process of the forced vibrations of a cylindrical shell stiffened with longitudinal ribs is developed. The shell is under an exciting load of variable frequency and amplitude. The technique takes into account the discrete arrangement of ribs. The effect of the number of ribs on the deflection of the shell during a transient is studied. [ABSTRACT FROM AUTHOR]