Asçi, Nurcan; Uysal, Habib; Uzman, Omit; Inan, E; Kiris, A

In this paper, optimization of a spherical shell under various dynamic loads is investigated. The aim of this optimization problem is to minimize the volume of the shell. Design variables are corner thicknesses of each finite element. Constraints are stresses obtained from von Mises stress criterion not to exceed the yield stress in corner nodal points of each finite element at the top and bottom surfaces of shell and thicknesses are restricted not to be less than 2.5 mm. In addition to shell's own weight, the vertical loads with equal intensity are applied at the nodal points on the upper edge of spherical shell, varying with respect to time function P(t). Time varying load vector is considered three different cases such as step, step after ramp and impulse functions. A program is coded with MapleV for optimization of spherical shell and finite element package program ANSYS is used for structural analysis. Obtained results are presented in graphical and tabular form. Finally, concluded remarks are given.

Uysal, Habib; Gul, Rustem; Uzman, Umit

A finite element-based shape optimization program has been developed for three-dimensional shell structures and the shape optimization of shell structures has been performed. The shape optimization program is implemented by a job control language and a reliable finite element package program, ANSYS, is used for structural analysis. To achieve the shape optimization, different principles such as structural analysis, automatic mesh generation, sensitivity analysis and mathematical programming are inter-related. The objective is to minimize the weight of the shell structure under constraints that are the maximum value of the von Mises stress in each element and the move limit for each design variable. The design sensitivities are calculated using the finite difference method. The search for the final shape of a structure is performed using the linear programming technique. Several examples are provided.