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) –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 w 0, w f, l f, l 0 for 20% or 15% stretching. For rolled sheet ‘R’ value varies based on the direction of rolling.

R bar also depends on grain size and texture. –Cold rolled – R bar increases with increasing grain size. –Hot rolled – R bar is approximately equal to 1 since texture has random orientation. E bar is calculated similarly to R bar. 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