non linear analysis for superplastic forming

NON-LINEAR ANALYSIS FORSUPERPLASTIC SHEET METAL FORMING

KURIAN ANTONY

ME CAD/CAM

just4kurian@gmail.com

INTRODUCTION

Is the ability of materials to exhibit exceptionally high tensile ductility

Superplastic materials may be stretched in tension to elongation typically in excess of 200% and more commonly in the range of 400-2000%

High ductility is obtained only for superplastic materials and requires both the temperature and rate of deformation (strain rate) to be within a limited range

SUPERPLASTICITY

It is at this state that the material subjected to loading behave non-linearly, ie tends to yield and therefore the stress-strain curve is no more linear.

NON-LINEAR ANALYSIS

Literature Review Production Technology H.M.T

Manufacturing Engineering and Technology Serope kalpakjian Steve R.Schmid

Finite Element Analysis of Sheet Metal Forming Process Hakim S. Sultan Aljibori Journal : European journal of scientific research Volume : 33, 57-69 Year :2009 This paper was carried out to study the finite element analysis of sheet metal forming

process using the finite element software. Simulation of elastic plastic behavior of sheet metal was carried out under non-linear condition to investigate sheet metal forming process.

Sheet Metal Forming William F. Hosford and John L. Duncan Journal :JOM volume :51, 39-44 Year :1999 This paper shows how experimental and theoretical contributions have led to the concept of forming

sheet metal under different condition.

The Current State-of-the-Art and the Future in Airframe Manufacturing Using Superplastic Forming Technologies

Daniel G . Sanders Journal : Material Science Forum Volume : 357-359 Year : 2001 Advantages of superplastic forming over conventional are Freedom of design, The ability to build large assemblies with fewer pieces, Inventory reduction,

through-put improvements and cycle time reduction. Cost and weight savings

Contd… Superplasticity in titanium alloys J.Sieniawski , M.Motyka Journal : Journal of Achievements in Materials and Manufacturing Engineering Volume : 24 Year : 2007 This paper discuss about the effect of microstructure on superplasticity of titanium alloys and also about

mechanical properties of superplastically deformed titanium alloys

Thermal Behaviour modelling of superplastic forming tools Vincent . Velay , Thierry Cuter , Nicolas Guegan Journal :Euro Volume: 27 Year :2008 This paper discuss on at high temperature the superplastic forming tools induce a very complex thermo

mechanical loadings responsible to failure.

Optimization of superplastic forming processes using the the finite element method

Hambli, R. Kobi Journal :IEE Volume :5 Year :2002

In this paper the analysis of the superplastic sheet-forming process is studied by the use of the finite element method.

SOTWARE USED

CATIA

M.S.C MARC MENTANT

MATERIAL SELECTED

Ti-6Al-4V

MECHANICAL PROPERTIES OF Ti-6Al-4V

Tensile strength (Mpa) 1000

Proof stress (Mpa) 910

Elastic modulus (Gpa) 114

Strain rate (s-1) -10-4

PHYSICAL PROPERTIES OF Ti-6Al-4V

Density (g/cm2) 4.42

Melting range(0c) 1649

Specific heat(J/Kg0c) 560

SPECIFICATION OF THE MODEL

Radius of dome : 25mm

Thickness of sheet: 1 mm

Strain rate : .004s-1

Strain rate sensitivity: 0.65

Strength co-efficient of sheet metal: 1106.45

MODEL

THEORETICAL MODELLING

P=pressureK=Co-efficient of friction of sheet metalƐo=strain rate sensitivitySo=initial blank thicknessT=timea=die radius

Pole thickness Sp= So exp(-ɛt)

Radius of curvature ρ = a So

2 sp (so-sp)

Height of the dome h = ρ – ρ2 - a2

PRESSURE VS TIMETime(sec)

Pressure(Mpa)

9 1.06

15 1.32

17 1.39

19 1.44

21 1.50

31 1.70

133 1.73

150 1.63

172 1.56

200 1.34

TIME,POLE THICKNESS AND DOME HEIGHT

Forming Time(sec)

Pole Thickness(mm)

Dome Height(mm)

0 0 0

9 0.9 7

15 0.9 9

31 0.8 11

52 0.75 13

72 0.70 15

92 0.65 17

112 0.63 19

136 0.60 21

172 0.56 23

200 0.53 25

ANALYTICAL RESULTS

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

20 40 60 80 100 120 140 160 180 200

time (sec)

pres

sure

(mpa

)

DOME HEIGHT VS POLE THICKNESS

0

5

10

15

20

25

30

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

pole thickness (mm)

Dom

e H

eigh

t(mm

)

DOME HEIGHT VS TIME

0

5

10

15

20

25

30

20 40 60 80 100 120 140 160 180 200

Time(sec)

Do

me

Hei

gh

t(m

m)

FEA RESULTS

MARC-MENTAT software is utilized in the present finite element model for Superplastic forming of Titanium alloy hemispherical domes.

The quarter model is defined using four noded isoperimetric membrane elements. The elements contains only thee translational degrees of freedom at each node , no bending stiffness is included in the formulation.

Uniform pressure is applied on the work piece.

THICKNESS DISTRIBUTION

Material – Ti 6Al 4VTemperature – 9270 cStrain rate – 4e-3 / secInitial blank thickness – 1mmDie radius – 25 mm

Finite element model of initial blank with die for dome (Quarter model )

ANALYTICAL VS FEA RESULTS

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

20 40 60 80 100 120 140 160 180 200

time (sec)

pre

ss

ure

(m

pa

)

Series1

Series2

Series1- Analytical ResultSeries2- FEA Result

CONCLUSION &RECOMMENDATION

Simulation of superplastic forming process has been carried out using FE method with MARC-MENTAT software

The analysis results show that the dome thickness is more uniform

at lower heights. This approach can be extended to complex product geometries also.

Analytical models generated by various researchers have been reviewed and a simple model suggested for thickness profile is considered in this work for validation through FE methods

This model can be used for the development of a computer program to generate thickness profile of a gas pressure formed spherical dome at any instant of time during the bulging process.