Experimental investigation of the effects of blank holder geometry and lubrication
on strain distribution in deep drawing
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1
Engineering Technical College - Baghdad, Middle Technical University, Baghdad 10074, Iraq
2
Institute of Technology-Baghdad, Middle Technical University, Baghdad 10074, Iraq
Corresponding author
Ahmed Ghanim Saleh
Engineering Technical College - Baghdad, Middle Technical University, Baghdad 10074, Iraq
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ABSTRACT
The present paper investigates the key role of blank holder geometry on strain distribution and defect formation during deep drawing of monolithic sheets (aluminium 1060 H14 and brass CuZn10). Four blank holder forms (flat, inclined, concave and convex) were studied with two different tribological conditions (oil and grease). The experimental study concentrated on the evolution of punch loads, strain paths (radial, hoop and thickness), and geometrical accuracy. Results indicate that the convex shape is absolutely non-deep drawable (100 % failure) because of its high counter-bending force value. In addition, the concaved holder with decreased wall-thinning by “hydrostatic cushion” was unable to impose restraining force sufficient to restrict the rim wrinkle. On the other hand, among those geometries the inclined holder (taper 15°) was found to be die geometry, which offers better durability and could produce high-hardenability brass with more stable process than the flat die illustrating a failure ratio. Strain analysis showed that the ironing effect, caused by the inclined die, is mechanically necessary for generating high hoop tension to get defect-free cups. Besides, a wedging effect is observed between viscous lubricants: the grease works as a viscous damper, balancing flow ease with necessary restraint particularly for aluminium.