The influence of defects on the dynamic characteristics of three-layer cylindrical shell structures

With repeated use of shell structures, specific problems arise in theoretical studies of the influence of the appearance of various structural cracks on the dynamic characteristics of three-layer cylindrical elements with inhomogeneous filler under different boundary conditions. Studies of the influence of such cracks on the dynamic characteristics of shell elements with inhomogeneous filler are quite important and relevant.The theoretical study of the natural frequency spectrum of a three-layer cylindrical shell with a discretely symmetric light, ribbed filler in the presence of annular cracks has been conducted. The finite element method solves the current problem of determining the natural frequencies of a three-layer element of special equipment under different boundary conditions.When studying such cylindrical shells, two types of defects were considered - through-through circular cracks in the reinforcing ribs of structures and three cases of their location. Frequency spectra are given for different types of boundary conditions. For typical cases of rigid clamping without foam plastic and hinged fastening with foam plastic, the shapes of the corresponding natural frequencies are additionally given for visualization.The analysis of the obtained numerical results made it possible to determine the nature of the influence of cracks of different lengths on the frequency spectra of three-layer cylindrical shells with a inhomogeneous filler.Frequency analysis of a three-layer cylindrical element for the presence of defects showed that the presence of a crack in the edge of the structure is a significant factor affecting the natural frequency of such an element and essentially leads to structural changes in this element.The obtained theoretical results indicate that small cracks have a small influence on the natural frequency of the structure. When relatively large cracks occur, a significant change in the frequency spectrum of an almost new three-layer structure is observed.