Abstract.The problem of maximizing the stiffness of a linearly elastic sheet, in unilateral contact with a rigid frictionless support, is considered.The design variable is the thickness distribution, which is subject to an isoperimetric volume constraint and upper and lower bounds.The bounds may vary over the domain of the sheet, and the lower one is allowed to be zero, hence giving the possibility of obtaining topology information about an optimal design.By using saddle point theory, the existence of solutions, i.e., thickness functions and corresponding displacement states, is proved. In general, one cannot expect uniqueness of solutions, unless the lower bound is strictly positive, and the uniqueness of optimal states is shown in this case.
Introduction.Traditionally, one categorizes structural optimization into three major groups: sizing, shape, and topology optimization problems. The first deals with, e.g., choosing optimal thicknesses of a (two-dimensional) structure, the second involves picking a good shape of the boundary to the domain occupied by the structure, and the last one concerns holes in and connectivities of the domain. The problem considered in this paper, namely that of finding a thickness distribution in a linearly elastic sheet, such that a suitable objective functional is extremized, can clearly be put in the first category. However, by allowing the design variable to be equal to zero, one obtains in effect (also) a topology optimization.Moreover, if the design is a distributed parameter, as in the case of a thickness distribution in a sheet, a solution will also generate a three-dimensional shape.