One of the most common material working operations is bending. This process is used not only to form parts such as flanges, seams etc. but to impart stiffness to the part by increasing its moment of inertia.The terminology used in bending. Spring back can be defined as elastically-driven change of shape of a deformed product which takes place during removal of external loads. It is a complex physical phenomenon there are several types of spring back in sheet metal.The outer fiber of the material are in tension and the Inner fiber of the material are in compression.

Introduction

Aim The main object of the project is to design and manufacturing bending die and determine the spring back phenomena of lead , aluminum and copper alloys. By keeping all the variable constant except the thickness. The die is unconstrained cylindrical bending . The thickness of alloys specimens are 2mm and 4mm.

Preparation & manufacturingManufacturing

flow diagramPreparation of

sheets

Casting Rolling Trimming

Manufacturing the die and the punches

• The preparation of the sheet metal alloys done by three stages to reach the final dimension of the sheets 2 , 4 mm thickness

The unconstrained cylindrical bending die and its punches is from carbon tool steel U10.manufacturing by milling and lathe machine. The first punch with R20.5 used to bend the sheet of 4 mm and the second punch R22.5 used to bend the sheet of 2 mm and the die radius 25 mm

ResultsDifferences between 2mm and 4 mm sheets metal alloy thicknesses and springback is shown in (fig.)

sprin

gbac

k

Fig. springback in sheetsAs shown in (fig.) the springback K in lead sheets increase with the increase of it’s thickness. While in copper and aluminum sheets the springback factor K decrease with the decrease of it’s thickness.The aluminum sheets have the highest springback and the lead sheet of 2 mm thickness indicate no springback

Experiment • punching

• Measuring

conclusion

References

1. J.R. Cho, S.J. Moon and S.S. Kang, Finite Element investigation on Springback, 2003, 141(1), 109-116. 2. Wagoner, R. H. and Li, M. Simulation of springback, 2007, 23, 345-360 3. Gan,W. and Wagoner, R.H. Die design method for sheet springback. Int. J. Mech. Sci., 2004, 46, 1097-1113. 4. Schmoeckel, D. and Beth, M. Springback reduction in draw-bending process of sheet metals 1993, 42(1), 339-342.

Aluminum Copper lead

The spring back factor (K)

i. When the hardness of the sheet increase the springback back factor (K) increase the sheets hardness Al. , Cu and Pb ( 72 ,57 , 36HRC ) respectively

ii. The springback factor K=1 in lead alloy of 2 mm thickness that indicate there is no spring back in the sheet iii. Changing in the thickness of the sheet have big effect on the spring backiv. Aluminum sheets (AA7020 T6) have the biggest springback factor Kv. In Al and Cu when the thickness increase the spring back factor increase while in Pb alloy when the thickness increase

the springback factor decrease

Edited by the student 1.Manar Emad Mohammed2.Mohammed Ali Fadhil3.Mustafa Nabel Talib4.Rand Murtadha Awad

supervisorAsst. Prof. Dr. Hani Aziz Ameen

In Bending ,after plastic deformation there is an elastic recovery this recovery is called spring back.

Spring back can be calculated approximately in terms if radii Ri and Rf

Ri/Rf = 4 ( Ri Y / ET )3 – 3 (Ri Y /ET) + 1 Spring back Increases as (R/T ratio &

yield stress of material ) increases as elastic modulus E decreases

Sb% As% Bi% Cd% Cu% Fe% Mn%0.002 0.0005 0.005 0.0005 0.003 0.001 0.0005Ni% Se% Ag% Te% Sn% Zn%  0.001 0.0005 0.002 0.0005 0.001 0.002  

Table 3: Chemical Composition of the lead

Zn% Pb% Sn% P% Mn% Fe% Ni% Si% Al% S%

0.01 0.02 0.01 0.007 0.002 0.005 0.02 0.006 0.014 0.003

Ag% Co% Cu%              

0.005 0.01 99. 5              

Table 1 : Chemical compositions of copper sheets.

Elements Standard value Measured value Si < = 0.35 0.121Fe < = 0.40 0.290Cu < = 0.20 0.200Mn 0.05 - 0.5 0.0764Mg 1 -1.5 1.25Cr 0.10 – 0.35 0.228Zn 4 – 5 4.56Ti 0.08 0.0319Al BALANCE BALANCE

Table 2 :The Chemical Composition of 7020 Alloy

Design & manufacturing the bending die to study the

phenomena in metal alloys

DIAMENSION WORCH SHOP DIAMENSION WORCK SHOP PART NAME

45 X 40 Grinding 45 X 40 Turning Punch 1

120 X 50 X 50 MILLING 50 X40 Turning Die 41 X 40 Grinding 41 X 40 Turning Punch 2

Springback