The deformation characteristic of drawing process is to change the large cross-sectional area of blank into a cylindrical part with small cross-sectional area. The so-called stretching coefficient is the ratio of the cross-sectional area after each stretching to the cross-sectional area before stretching:

That is m=An/An- 1.

M- tensile coefficient

An-cross-sectional area after stretching (mm? )

An-1-cross-sectional area before drawing (mm? )

For cylindrical parts, the tensile coefficient should be:

m = An/An- 1 =(πDNT)/(πdn- 1t)= dn/dn- 1

Where m is the tensile coefficient of cylindrical parts.

Dn- diameter after drawing (mm? )

Dn- 1—— Diameter before drawing (mm? )

T- material thickness

The drawing coefficient of cylindrical parts is the ratio of the diameter of cylindrical parts after each drawing to the diameter of blank (or semi-finished product) before drawing. Namely:

The first drawing m0=d 1/D0

Subsequent deep drawing m2=d2/d 1, m3=d3/d2, ..., mn=dn/dn- 1.

Where m 1, m2, m3.....m0 is the tensile coefficient for each time.

D0- blank diameter (mm? )

D 1, d2, d3, ... d0 —— the diameter of each semi-finished product or workpiece (mm? )