# To equistability problem of the reinforced shell structure under combined loading

 1Degtyarenko, PG, 2Grishchak, VZ, 3Grishchak, DD, 4Dyachenko, NM1Yangel Yuzhnoye State Design Office, Dnipro, Ukraine2Dnipro University of Technology, Dnipro, Ukraine3Central Scientific Research Institute for Armament and Military Equipment of the Armed Forces of Ukraine, Kyiv, Ukraine4Zaporizhzhia National University, Zaporizhzhia, Ukraine Space Sci. & Technol. 2019, 25 ;(6):03-14 https://doi.org/10.15407/knit2019.06.003 Publication Language: Russian Abstract:  The stability of a cylinder-cone-type shell structure of the launch vehicle is studied under the combined loading of external pressure, axial compression, and torque. The resolving equations for the problem are solved analytically using the asymptotic approach. In the case of the conical compartment, two analytical methods, such as the WKB and the hybrid WKB-Galerkin methods, are used. To analyze the stability of the reinforced shells, we use the matrix method that allows determining the change in the shell stressstrain state through the ring. The characteristic equation for determining critical loads is obtained based on the matrix method and the conjugation equations. Particular attention is paid to the selection of ring stiffness coefficients for the conic al and cylindrical parts providing equal critical pressures. It is obtained that the values of the critical pressure in the equistable structure are lower than in its parts.             The stability of the reinforced equistable structure under the combined loading is studied. The results of numerical calculations for different types of reinforced structures are discussed. It is shown that in the extreme cases, for cylinder or conical shells, numerical results are well correlated with data of known publications. Keywords: combined loading, cylinder-cone-type shell structure, equistable shell, ring stiffness, shell stability
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