Model for Layer-by-Layer Analysis of the Stress-Strain State of Three-Layer Irregular Shells of Revolution of Double Curvature

Based on the layer-by-layer analysis approach, the construction of a model of two types of finite elements (FE) of natural curvature (two-dimensional FE of the momentary bearing layers and three-dimensional FE of the filler) is considered for refined investigation of the stress-strain state (SSS) in layers of three-layer generally irregular shells of revolution of double curvature. The presented model-building algorithm allows one to avoid errors due to the discontinuity of generalized displacements on the docking surfaces of the FE of the bearing layers and the aggregate, to analyze the SSS for all three coordinates to which the shell is assigned, and to obtain a solution in an updated statement for various shell shapes and boundary conditions of the layers, as well as violations of their continuity. At the same time, the aggregate layer can be modeled in thickness by the required number of finite elements, which allows one to take into account the change in geometric characteristics, physical and mechanical properties, and SSS parameters not only in the meridional and circumferential coordinates, but also in the thickness of the shell and aggregate layer. The proposed approach significantly expands the range of problems solved in the refined formulation and allows us to carry out the calculation with a high degree of accuracy and detail. As an example, the calculation of the SSS of a three-layer animated casing with cut-outs is given. The influence of the size of the cut-outs on the stress - strain state in the layers of the three-layer shell of rotation of double curvature is studied.