Curved surface forming method of a metal plate

A method of forming a metal plate into a desired shape having a curved surface using a multi-point dieless forming apparatus having a plurality of forming punches, the method comprising the step of:

• (a) inputting basic information including dimensions and physical property values of the metal plate to be worked into a computer system in which a program for nonlinear finite element analysis of elasto-plastic large deformation is installed;
• (b) defining a target curved surface of the to-be-worked metal plate by CAD work on the computer system;
• (c) determining, using the computer system, a relative distance between the target curved surface and a surface of the to-be-worked metal plate;
• (d) performing, using the computer system, the finite element analysis of elasto-plastic large deformation on the to-be-worked metal plate based on the input basic information, and obtaining a first load-displacement relation;
• (e) arranging positions of multiple forming punches of a forming apparatus connected to a hydraulic apparatus so as to dispose them in a vertical direction;
• (f) determining a second load-displacement relation required for forming at a position of each forming punch using the first load-displacement relation that is obtained from the finite element analysis performed by the computer system;
• and
• (g) receiving information on the determined loads from a controller connected to the forming apparatus, performing numerical control on the hydraulic apparatus through the controller, and forming the to-be-worked metal plate loaded between the forming punches arranged at upper and lower positions so as to approximate the target curved surface.