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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