non linear analysis for superplastic forming

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NON-LINEAR ANALYSIS FOR SUPERPLASTIC SHEET METAL FORMING

KURIAN ANTONY ME CAD/CAM just4kurian@gmail.com

INTRODUCTIONSUPERPLASTICITY

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 4002000% 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

NON-LINEAR ANALYSIS

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.

Literature Review

Production TechnologyH.M.T Manufacturing Engineering and Technology

Serope kalpakjian Steve R.SchmidFinite Element Analysis of Sheet Metal Forming Process

Hakim S. Sultan Aljibori Journal : European journal of scientific research Volume : 33, 57-69 Year :2009This 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 :1999This 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 : 2001Advantages 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 alloysJ.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 toolsVincent . 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 methodHambli, 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=pressure K=Co-efficient of friction of sheet metal o=strain rate sensitivity So=initial blank thickness T=time a=die radius

Pole thickness Sp= So exp(- t) Radius of curvature = a So 2 sp (so-sp) Height of the dome h = 2

- a2

PRESSURE VS TIMETime (sec) 9 15 17 19 21 31 133 150 172 200 Pressure (Mpa) 1.06 1.32 1.39 1.44 1.50 1.70 1.73 1.63 1.56 1.34

TIME,POLE THICKNESS AND DOME HEIGHTForming Time (sec) Pole Thickness (mm) Dome Height (mm)

0 9 15 31 52 72 92 112 136 172 200

0 0.9 0.9 0.8 0.75 0.70 0.65 0.63 0.60 0.56 0.53

0 7 9 11 13 15 17 19 21 23 25

ANALYTICAL RESULTS2 1.8 1.6 1.4 ) 1.2 ( 1 0.8 0.6 0.4 0.2 0 20 40 60 80 100 120 ( ) 140 160 180 200

DOME HEIGHT VS POLE THICKNESS

30 25 20 15 H 10 D 5 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

DOME HEIGHT VS TIME30 25 20 15 H 10 D 5 0 20 40 60 80 100 T 120 140 160 180 200

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 4V Temperature 9270 c Strain rate 4e-3 / sec Initial blank thickness 1mm Die radius 25 mm

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

ANALYTICAL VS FEA RESULTS2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 20 40 60 80 100 120 140 160 180 200 Series1 Series2

Series1- Analytical Result Series2- 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.

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