Using the large displacement theory (theory of the third order according to Chwalla), this paper deals with the lateral buckling process of a slender, elastic cantilever beam with a changeable height of a rectangular cross section and represents it with a system of nonlinear differential equations. Based on a mathematical model of the lateral buckling process, which considers the geometric and boundary conditions, an optimal geometry of a cantilever beam is obtained using the calculus of

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... on. A comparison between the properties of the beam with optimized geometry and those of a referential beam with a constant cross section is shown. The result of the optimization process is, besides a higher critical load, a higher carrying capacity of the optimal geometry beam in the postbuckling region. For a verification of the theoretical results an experiment of the lateral buckling process had been done. ϑ that are in the interval [0,1] continuous and continuously differentiable, we are looking for the one that would give a minimum value to functional ( ) ϑ J . Computer Aided Optimum Design in Engineering X 71