The study is concerned with the investigation of curved line folding of developable surface from flat sheet.
General geometric relations among folding line, folded surface, folded angle are derived. From the derived geometric relations, the required plastic work and punch force are derived for the first approximation.
The folding line must lie on one plane and the two folded surfaces are conjugate surfaces.
Five methods of forming are suggested and the experiment is carried out using two chosen methods for the prismatic developable surfaces of which cross sections have 103˚ arc, 180˚ arc, sinusoidal shape.
In the die design for the folding of prismatic developable surfaces, a stack of sheets were used to form shapes of the dies by which acceptable folded surfaces were obtained.
The computed plastic work and punch force turned to be rather higher than experimental results because of rough approximations, but this leave safe margins for the die design.