Abstract: Based on lots of drawing experiments, considering the stress and strain state of the flange and the bottom of rectangular case with variation of load, it is analysed that the blank holder force brings very complex effect on load of drawing even on the load of fracture in a larger non-rotational symmetry deformation of sheet metal vs. punch radius. It is pointed out that the coefficient of slip friction in the flange corner is quite sensitive to blank holder force in a forming process, and directly affects the stress and strain state of the flange and the part in danger of fracture. Especially at the later stage of forming with higher surface pressure, lubrication effect at flange turning worse leads to drawing load increasing and forming limit decreasing.

Key words: Blank holder force, Friction resistance, Lubrication, Non-rotational symmetry drawing