LITERATURE REVIEW ON DEEP DRAWING

To determine the process characteristics and different parameters influencing the process many

useful research papers were studied by us. Some of them are mentioned bellow which gives the

idea about the process technology and parameters with their effects.

S. Yossifon, J. Tirosh [1] has investigated the feasibility of replacing the rigid blank-holder in

the conventional deep drawing process with a fluid assisted blank holder. The advantages of this

technique mentioned by the author are:

1. By properly controlling the fluid pressure, premature wrinkling and premature rupture can be

avoided.

2. It is possible to draw relatively thin blanks

3. Higher repeatability of the product is expected, as a result of the precise control of the fluid

pressure.

Fig. 2.1.1- Deep drawing system with fluid assisted blank holder

The recommended fluid pressure range (the ‘working zone’) which guarantees a sound product

in different circumstances is presented in this paper. The locus curve, for possible failure by

wrinkling of the flange and the locus curve for possible ductile rupture along the wall provide the

lower and the upper limits respectively of the ‘working zone’. These loci are found by a

systematic series of deep drawing tests with different or constant fluid pressure of blank-holder

for three kinds of materials (copper, alluminum and stainless steel) at various thicknesses and

friction conditions. The influence of the friction coefficient, the drawing ratio and the work piece

wall thickness on the blank-holder fluid pressure needed to suppress flange wrinkling becomes

evident experimentally.

The author concluded that the FAB process seems to work satisfactorily within certain fluid

pressure limits. Thinner blanks call for high fluid pressure to suppress wrinkling. A higher

friction coefficient between the blank and the die leads to lower fluid pressure to suppress

wrinkling. The higher the drawing ratio the less fluid pressure is needed to suppress wrinkling

Thus the parameters like BHF, friction and drawing ratio can be studied with this paper.

S. Thiruvarudchelvan, M.J. Tan [2] stated that Hydraulic pressure can enhance the capabilities

of the basic deep drawing process for making metal cups. Amongst the advantages of the

hydraulic pressure assisted deep drawing techniques, increased depth-to-diameter ratios and

reduced thickness variations of the cups formed are notable. Hydraulic pressure contributes

positively in several ways to the deep drawing process. Different combinations of these positive

effects of hydraulic pressure on deep drawing are found in the existing hydraulic pressure

assisted deep drawing processes.

The authors have focused on the two important effects:

(a) Hydraulic pressure pushing on the periphery of the flange of the cup, thereby contributing to

the externally supplied work for deformation.

(b) Hydraulic pressure in the die cavity helping to generate frictional support of the cup wall so

as to enable the work-hardened metal at the die throat to carry a larger draw stress.

Thus they conclude that as drawing progresses this pressure helps via friction to take advantage

of the increased flow stress of the strain-hardened cup wall. Frictional support of the cup wall

will develop as the depth of the cup increases. Both hydraulic pressure and the increased flow

stress of the cup wall at the die throat are crucial for providing the work of deformation until it

reaches the maximum value: as a consequence, larger draw ratios can be achieved.

Huiting Wang, LinGao, MingheChen [3] described a modified method, named hydrodynamic

deep drawing assisted by radial pressure with inward flowing liquid and it was proposed and

investigated using both primarily experimental and numerical simulation analysis.

Fig. 2.1.2- Radial pressure system and the formed cups

Radial pressure can reduce drawing force and increase drawing ratio in hydrodynamic deep

drawing. However conventional hydrodynamic deep drawing cannot attain a radial pressure

higher than the pressure in the die cavity. A radial pressure higher than the pressure in the die

cavity was realized by means of the inward flowing of the liquid during this process. After

preliminary experimental validation, FEM was used to explore the forming process. The results

from the simulation were compared with those from the experiment. The effects of the radial

pressure on the wall thickness distribution, punch force, and compressive stress in the blank

flange were studied with assistance of numerical simulation. The process window for radial

pressures versus drawing ratios was established in 2Al2O alloy experimentally and cups with

drawing ratio of 2.85 were successfully formed.

Strain diagram showing a typical forming limit curve for steel blanks