Abstract: Method for aiding sheet metal forming tool design, for use with a computer including memory, and forming tools including a draw die, punch and binder having surfaces designed to form the sheet metal into a part, the sheet metal being represented as a mesh including a plurality of nodes. The method includes evaluating an initial binder-set associated with an initial binder surface design during a first stage of forming the sheet metal in which at least one of the plurality of sheet metal mesh nodes is forced against the binder surface, and detecting an area of unacceptable deformation on the sheet metal mesh. The method also includes identifying the at least one of the plurality nodes forced against the binder surface associated with the unacceptable sheet metal deformation and releasing the at least one of the plurality of nodes identified, so as to allow the identified nodes to move as the sheet metal assumes a relaxed state.

Abstract: Method for predicting post-buckling deformation of a sheet of metal during a draw forming process, for use with a computer including memory, by introducing a set of springs to stabilize the sheet metal close to the onset of buckling, thereby enhancing convergence of numerical solutions. The method is for use with sheet metal forming tools including a draw die, a punch and binder having surfaces designed to form the sheet metal into a part, the sheet metal being represented as a mesh including a plurality of nodes. The method includes applying a displacement increment to the sheet metal nodes and identifying a singularity in a tangent stiffness matrix associated with the sheet metal close to the onset of buckling. The method also includes introducing a plurality of springs at the sheet metal nodes so as to eliminate the singularity and enhance convergence of the numerical solution of the displacement increment.

Abstract: Method and system for evaluating sheet metal forming tooling design, for use with a draw die including a punch and binder designed to form the sheet metal into a part, utilizing improved implicit time integration methods that reduce numerical instability, thereby enhancing convergence of numerical solutions. The sheet metal and tool surface of the punch are each represented as a mesh having a plurality of nodes. Contact nodes between the sheet metal mesh nodes and the tool surface mesh can be identified. A first embodiment includes minimizing discontinuities generated by unloading by determining a stress increment of a sampling point in the sheet metal mesh according to an incremental deformation theory of plasticity. A second embodiment includes modelling a draw-bead as a plurality of nonlinear elastic springs to minimize discontinuities in the spring force during unloading.

Abstract: Method of rapidly determining a binder wrap for a nonsymmetrical polygonal panel to be drawn formed, comprising: (a) forming a coordinate-based model of the blank outline of said panel; (b) specifying the displacement boundary condition of the binder wrap by nonlinear theory of mechanics, including: (i) defining arc sets to fit projections of opposite sides of the blank outline, having the greatest curvature, onto arc planes while incrementally bending the panel from a known flat condition to a binder surface condition and controlling each arc set to pass through a fixed point as it is changed in radius, (ii) interpolating from said arc sets to generate points on the unprojected opposite sides having such greatest curvature and thus defining the binder surface for the blank outline along such sides, (iii) defining the binder surface for the blank outline along sides having the least curvature by forcing such sides to lie on the binder surface through the act of proportionally reducing the gap or interference