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Deep Drawing. Inportant factors of deep drawing. Properties of the sheet ratio of blank dia and punch dia clearance punch and die corner radii speed of punch holding force etc. Deep Drawability. Limiting drawing ratio (LDR) Max D 0 /D p ratio R (normal anisotropy)
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Inportant factors of deep drawing • Properties of the sheet • ratio of blank dia and punch dia • clearance • punch and die corner radii • speed of punch • holding force etc
Deep Drawability • Limiting drawing ratio (LDR) • Max D0/Dp ratio • R (normal anisotropy) • If R=1 sheet is isotropic.
For a gage length of ‘l’ and subscript ‘o’ and ‘f’ are original and final dimension. • R can be calculated by measure w0, wf, lf, l0 for 20% or 15% stretching. • For rolled sheet ‘R’ value varies based on the direction of rolling.
Rbar also depends on grain size and texture. • Cold rolled – Rbar increases with increasing grain size. • Hot rolled – Rbar is approximately equal to 1 since texture has random orientation. • Ebar is calculated similarly to Rbar. Planar anisotropy causes ‘ears’ to occur.
Case Study Beverage cans – Page 395/396 of the text book
Formability of Sheet Metal • Cupping test – Erichson test 1000kg • Bulge test – Hydraulic pressure no friction involved • Forming limit diagram • Grids are marked on the sheet • Sheets of several widths