Abstract: The general solution for the critical instability load of cup-drawing is deduced by applying the theory of plastic flow and the criterion of tensile plastic instability, which is based on three kinds of the hardening curve of materials most in use. The formula mirrors the effect of normal anisotropy of a plate, work-hardening and punch geometry on the solution. The cup-drawing test to four kinds of sheet metal expresses that the relative errors between the theoretical solutions and the experimental results are within 5%. It is analyzed that the special solutions based on different hardening curve are separately suited what sort of metals. And it is pointed that neglecting normal anisotropy or fitting non-matched equation into experimental hardening curve will produce evident influence for precision of the solution. The general solution advanced is suitable for drawability analyzing of most of sheet metal.

Key words: Deep-drawing, Drawability, Stamping