The mechanical behavior of perforated plates is simulated by the analysis of homogenized (unperforated) plates. The material properties of the homogenized plate are tuned to be equivalent to the global properties of the perforated plate. The homogenized material properties of a perforated plate are determined by finite element calculations on a representative volume unit (RVU) of the plate. A set of essential boundary conditions for the RVU is specified such that any loading path in the homogenized (plane) stress space can be followed. A method to scan the homogenized plane stress space in order to determine the initial yield surface is presented. Also, the evolution of the yield surface is established by systematic scanning. This evolution justifies the assumption that the actual yield surface is controlled by three internal history parameters. The resulting yield surface and its evolution cannot be described accurately by a Hill-type yield function. Therefore the modeling is performed by the application of so-called non-uniform rational basis (NURB) polynomials. Special routines are developed to implement the associated algorithms in a commercially available finite element package.