Physical tools for trimming operations in forming of a sheet-metal part are set up based on numerically-simulated structural behaviors. FEA model representing a stamped sheet metal before trimming and a trimming operation setup are received. Each trim-steel contains a set of cutting-edge nodes associated with trim vector. At least one trim line is established by projecting cutting-edge nodes onto the FEA model according to the trim vector. Numerically-constrained node-pairs along the trim line are created at intersections with edges of crossed finite elements. FEA model is modified by splitting the crossed finite elements to preserve original geometry and to ensure numerical stability. New finite elements are defined using one of the nodes in corresponding node-pairs such that no finite element straddles the trim line. At each solution cycle of a time-marching simulation of trimming operations, simulated structural behaviors are obtained as the scrap portion(s) deforms and falls accordingly.