Krupko N. The stress state of isotropic shell with a circular hole and cracks

In the dissertation work the stress state of isotropic double curved shells, plates with stress concentrators was studied. The mutual influence of cracks (through or non-through thickness cracks) and hole (circular or elliptical) was analyzed in the constructions. To solve this problem we used the equations of the shallow shell theory, the method of boundary integral equations together with a line spring model. Due to these methods the boundary integral equations, which describe the stress state, were obtained. To ensure the uniqueness of the solution the extra equation, compatibility condition of deflection and rotation angles, was added to system. The given problem was reduced to a system of linear algebraic equations. The numerical solution is based on the use of the mechanical quadrature method and the finite difference method. The influence of the shell curvature, depth, length of cracks, a hole, the distance between the defects and the mutual arrangement on stress concentration factors for holes, stress intensity factors for through thickness cracks and normalized stress intensity factors for non-through thickness cracks was shown. The theoretical results of dissertation research can be used to calculate the structural elements with holes, cracks on the strength and fracture toughness in various branches of modern engineering and industry.