Hydro-Forming a Steel Hydro-Forming a Steel TubeTube

Finite Element Model DesignFinite Element Model Design

Greg WilmesGreg Wilmes

Finite Element MethodFinite Element MethodMIE 605 – Spring 2003MIE 605 – Spring 2003

Hydro-Forming of a Steel Hydro-Forming of a Steel TubeTube• BackgroundBackground

• Model CreationModel Creation– Model LimitationsModel Limitations– Contact elementsContact elements– Load steppingLoad stepping

• FindingsFindings

• Future WorkFuture Work

• ConclusionConclusion

BackgroundBackground

• Sheet Hydro-FormingSheet Hydro-Forming– HoodsHoods– RoofsRoofs

• Tubular Hydro-Tubular Hydro-FormingForming– Engine chassisEngine chassis– Frame RailsFrame Rails– Exhaust SystemsExhaust Systems

Hydro-Forming is a manufacturing process which forms complex shapes using uncompressible liquids.

Primer: Tube Primer: Tube HydroformingHydroforminga b

c d

FaxialFaxial

P

e

Derived from: Siempelkamp Pressen Systeme GmbH & Co.

f

Massachusetts Institute of TechnologyCambridge, Massachusetts Materials Systems Laboratory

Concerns During Concerns During Hydroforming ProcessHydroforming Process

Focus of this projectFocus of this project

• Create a Finite Element Model to Create a Finite Element Model to simulate the hydro-forming processsimulate the hydro-forming process

• Use the model to create a 3”x3” Use the model to create a 3”x3” square tube from a 3” round tube.square tube from a 3” round tube.

Real World Example Real World Example

• 3-D parts3-D parts

• Non-linear material Non-linear material propertiesproperties

• Material variationsMaterial variations

• Complicated geometry Complicated geometry with bends and with bends and depressionsdepressions

• FrictionFriction

Geometry SimplificationsGeometry Simplifications

• 2-Dimensional2-Dimensional

• SymmetricSymmetric

• Deformation from Deformation from Circle to SquareCircle to Square

• Rigid Target SurfaceRigid Target Surface

• Constant Thickness Constant Thickness 1.6mm1.6mm

Press

ure

Governing EquationGoverning Equation

• Hoop StressHoop Stress

t

rPy

t

rP

Material Property Material Property SimplificationsSimplifications

• Isotropic ExpansionIsotropic Expansion

• Non-LinearNon-Linear– Experimental tensile test Experimental tensile test

datadata– 20 points 20 points

• Coloumb Friction EffectsColoumb Friction Effects

• No strain rate effectsNo strain rate effects

Plastic Deformation of Low Carbon Steel

250

260

270

280

290

300

310

320

330

340

350

0 0.05 0.1 0.15 0.2

Strain

Str

ess

(MP

a)

Model CreationModel Creation

• Element TypeElement Type– Plane 42Plane 42

• 4 noded4 noded

• 2-Dimensional2-Dimensional

• Non-LinearNon-Linear

• OptionsOptions– Plane Stress OptionPlane Stress Option– Local Coordinate Local Coordinate

SystemSystem– Extra Shape Extra Shape

FunctionsFunctions

MeshingMeshing

• Hydro-Form DieHydro-Form Die– Rigid TargetRigid Target

• No mesh allowedNo mesh allowed

• Hydro-Form BlankHydro-Form Blank– Mapped MeshMapped Mesh

• AngledAngled

• Thickness splitThickness split

Contact ElementsContact Elements

• Allows modeling of Allows modeling of contact between contact between two objectstwo objects

• Used Contact Used Contact WizardWizard– Rigid TargetRigid Target– Deformable ContactDeformable Contact– No Separation No Separation

(sliding) option(sliding) option– Coloumb Friction Coloumb Friction

(0.27)(0.27)

Solution Control OptionsSolution Control Options

• StaticStatic– Quasi-Static EvaluationQuasi-Static Evaluation

• Non-Linear SolutionNon-Linear Solution

• Stepped LoadingStepped Loading

• Auto Time StepsAuto Time Steps

ConstraintsConstraints

• Target DieTarget Die– Fully constrainedFully constrained– Cannot MoveCannot Move

• Contact BlankContact Blank– Symmetrically ConstrainedSymmetrically Constrained

Load StepsLoad Steps

• Using a simple “do” loopUsing a simple “do” loop– Slowly increase internal pressureSlowly increase internal pressure– 380 MPa380 MPa

• Used second “do” loop Used second “do” loop – Maintain pressure for a period of timeMaintain pressure for a period of time

• Repeated for different meshing Repeated for different meshing configurations configurations

FindingsFindings Maximum Displacement

11.7

11.8

11.9

12

12.1

12.2

12.3

12.4

12.5

12.6

0 200 400 600 800 1000 1200 1400 1600

Elements

Dis

pla

ce

me

nt

(mm

)

• Difference between 90 elements and 1400 elements Difference between 90 elements and 1400 elements was 0.032mmwas 0.032mm

• 0.3% difference0.3% difference• Close to general manufacturing machining tolerancesClose to general manufacturing machining tolerances

Continued WorkContinued Work

• Refine Finite Element simulation to Refine Finite Element simulation to match real world partsmatch real world parts– 3-Dimentions3-Dimentions– Different materialsDifferent materials– Different deformation shapesDifferent deformation shapes

• Stress State analysisStress State analysis

Conclusion and ThoughtsConclusion and Thoughts

• The Finite Element Method and Ansys The Finite Element Method and Ansys seem to be appropriate for analyzing seem to be appropriate for analyzing this problemthis problem

• Model seemed as respond well with Model seemed as respond well with about 100 elements about 100 elements