Stress concentration problems by FEM system "GIFTS" in conjunction with pre- and post-processors optimal reinforcement of holes

The largest part of the thesis is concerned with developing pre- and post-processors for testing a General Purpose Interactive Graphically oriented FEM system "GIFTS" for analysis of stress distribution around openings of a variety of shapes, stiffened as well as unstiffened, in a plane elastic field. The problems that have been considered include elliptical holes of arbitrary eccentricity in the plane sheet subjected to any combination of two-directional tension-compression at infinity; neutral holes; equally strong outlines and some other optimal geometrical discontinuities.In a separate part of the thesis a plane elastostatic problem for a sheet having a circular opening and loaded by uniform biaxial stresses at infinity has been considered. The outline of the hole is reinforced by a rod which may resist only axial deformations. Variation of the cross-sectional area of this stiffener is supposed to be determined so that, firstly, the hoop stress at the adjacent edge of the sheet be uniform along the boundary of the hole, and, secondly, the von Mises stress concentration is minimized along the boundary.