Effect of blank holder types on drawing of mild steel round cup with flange

Dissertant

Shukur, Jalil Jabbar

Thesis advisor

al-Darraji, Karim M.

University

University of Technology

Faculty

-

Department

Department of Production Engineering and Metallurgy

University Country

Iraq

Degree

Master

Degree Date

2013

English Abstract

This work aims to study the effect of change in blank holder geometrical shape on deep drawing operation.

In order to study this effect, the work has used two conventional types of blank holder (flat and gap), two sloping blank holders with o o angle (a=7.5 and a=15) and two types circular blank holder (concave and convex) each one with a curvature radius Rc=20, 25,30,35,40 mm.

A mild steel (1008-AISI) was chosen to carry out the work on, with sheet thickness of (t=0.5mm) and blank diameter (D=80 mm).

The die profile radius Rd =6mm and punch profile radius Rp = 6mm.

A commercially available finite element program code (ANSYS14.0), was used to perform the numerical simulation of the deep drawing operation.

Four types of 3-D models: flat, sloping, concave and convex have been developed.

Only one fourth portion of the model needed to be analysed, Due to the symmetry in the specimen geometry and applied load.

The Coulomb friction law with coefficients of friction of (^=0.1, 0.125, 0.15) and Von Mises yield criterion are employed in the numerical simulation.

Cylindrical cup of (40mm) inner diameter, (50mm) flange diameter and (25mm) height, was the final product in experimental and simulation work.

The parts were formed at a suitable punch speed of (55mm/min).

Two blank holder force was used; scheme A obtained when using spring with stiffness 280 N/mm, While scheme B obtained when using spring with stiffness 160 N/mm.To produce defect free cups, adequate blank holder force (scheme A) was used.

To study the effect of blank holder types on wrinkling formation, lower blank holder force (scheme B) was used.

The results show that the punch force decreases with increase in blank holder slope angle for sloping blank holder type, increases Rc also show decrease in punch force for convex blank holder, but the increase in Rc for concave blank holder leads to some increase in the value of punch force.

The cup wall thickness was more uniform when sloping blank holder was used o with angle (a=15) and with concave blank holder with Rc=20mm, where the thinning was reduced on punch profile zone and the thickening was minimized at flange zone along cup wall.

Sloping and concave blank holders had a greater ability to prevent wrinkling formation as evidenced by the maximum wrinkling height shown in convex and flat blank holders.

Good gradual diminution in circumference of flange to die cavity is one of the most important benefits obtained from geometrical shape of sloping blank holder; this property leads to decrease in hoop strain, thickening and wrinkling height in flange zone as compared with flat and gap types.

The obstruction force against metal flow results from increase in friction coefficient which diminishes when using sloping blank holder if compared with the friction force in flat blank holder.

The geometrical shape of concave blank holder has accomplished good flow path resulting from compatible unification between curvature radius (Rc) and die profile radius (Rd) and this is reflected on good thickness and strain distribution with low punch force.

Main Subjects

Engineering & Technology Sciences (Multidisciplinary)

Topics

• Mechanical properties

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-413073