Method for aiding sheet metal forming tooling design

A 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 with a drawbead, the forming tools 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 sheet metal mesh also including at least one spring node located at a boundary of the sheet metal, the method comprising the steps of:

• numerically determining by the computer the sheet metal mesh nodes contacting the punch and die tool surfaces due to the punch advancing to form the part and applying a position displacement increment to the nodes;
• modelling the drawbead by the computer as a plurality of nonlinear elastic springs, at least one nonlinear elastic spring being positioned at the at least one spring node and exerting an external force on the spring node which varies with nodal displacement, so as to minimize discontinuities in the spring force during unloading of the spring, thereby enhancing convergence of a numerical solution for the displacement increment to an equilibrium value;
• determining by the computer a strain and a stress distribution in the sheet metal due to the punch advancing to form the part;
• and
• reconstructing at least one of the forming tool surfaces based on the strain and the stress distribution, so as to prevent part failures.

A 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 and associated elements, the method comprising the steps of:

• numerically determining by the computer the sheet metal mesh nodes contacting the punch and die tool surfaces due to the punch advancing to form the part and applying a position displacement increment to the nodes;
• filtering by the computer a relative velocity vector associated with each contact node with respect to the punch and die tool surfaces;
• determining frictional forces by the computer at the contact node utilizing the filtered relative velocity vector, to avoid oscillations due to the change in direction of the relative velocity vector of the contact node, thereby enhancing convergence of a numerical solution for the displacement increment to an equilibrium value;
• determining by the computer a strain and a stress distribution in the sheet metal due to the punch advancing to form the part;
• and
• reconstructing at least one of the forming tool surfaces based on the strain and the stress distribution, so as to prevent part failures.

A system for aiding sheet metal forming tool design, for use with 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 and associated elements, the system comprising:

• input means for entering data representing the sheet metal mesh;
• means for storing the entered data and a predetermined instruction set;
• and
• a processor in communication with the input means and the means for storing, wherein the processor is operative to
• numerically determine the sheet metal mesh nodes contacting the punch and die tool surfaces due to the punch advancing to form the part and applying a position displacement increment to the nodes,
• to determine a stress state at at least one sampling point associated with the elements, so as to determine whether the stress state is unloading based on an incremental deformation theory of plasticity, and
• to determine for each unloading sampling point when the sampling point should change from a plastic state to an elastic state, so as to enhance convergence of a numerical solution for the displacement increment to an equilibrium value.

A system for aiding sheet metal forming tool design, for use with forming tools including a draw die, punch and binder with a drawbead, the forming tools 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 sheet metal mesh also including at least one spring node located at a boundary of the sheet metal, the system comprising:

• input means for entering data representing the sheet metal mesh;
• means for storing the entered data and a predetermined instruction set;
• and
• a processor in communication with the input means and the means for storing
• for numerically determining the sheet metal mesh nodes contacting the punch and die tool surfaces due to the punch advancing to form the part and means for applying a position displacement increment to the nodes, and
• for modelling the drawbead as a plurality of nonlinear elastic springs, at least one nonlinear elastic spring being positioned at the at least one spring node and exerting an external force on the spring node which varies with nodal displacement, so as to minimize discontinuities in the spring force during unloading of the spring, thereby enhancing convergence of a numerical solution for the displacement increment to an equilibrium value.

A system for aiding sheet metal forming tool design, for use with 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 and associated elements, the system comprising:

• input means for entering data representing the sheet metal mesh;
• means for storing the entered data and a predetermined instruction set;
• and
• a processor in communication with the input means and the means for storing
• for numerically determining the sheet metal mesh nodes contacting the punch and die tool surfaces due to the punch advancing to form the part and applying a position displacement increment to the nodes,
• for filtering a relative velocity vector associated with each contact node with respect to the punch and die tool surface surfaces, and
• for determining frictional forces at the contact node utilizing the filtered relative velocity vector, to avoid oscillations due to the change in direction of the relative velocity vector of the contact node, thereby enhancing convergence of a numerical solution for the displacement increment to an equilibrium value.