Hydro-Forming a Steel Tube Finite Element Model Design Greg Wilmes Finite Element Method MIE 605 – Spring 2003

Hydro-Forming of a Steel Tube Background Background Model Creation Model Creation –Model Limitations –Contact elements –Load stepping Findings Findings Future Work Future Work Conclusion Conclusion

Background Sheet Hydro-Forming Sheet Hydro-Forming –Hoods –Roofs Tubular Hydro-Forming Tubular Hydro-Forming –Engine chassis –Frame Rails –Exhaust Systems Hydro-Forming is a manufacturing process which forms complex shapes using uncompressible liquids.

Primer: Tube Hydroforming ab c d F axial P e Derived from: Siempelkamp Pressen Systeme GmbH & Co. f Massachusetts Institute of Technology Cambridge, Massachusetts

Concerns During Hydroforming Process

Focus of this project Create a Finite Element Model to simulate the hydro-forming process Create a Finite Element Model to simulate the hydro-forming process Use the model to create a 3”x3” square tube from a 3” round tube. Use the model to create a 3”x3” square tube from a 3” round tube.

Real World Example 3-D parts 3-D parts Non-linear material properties Non-linear material properties Material variations Material variations Complicated geometry with bends and depressions Complicated geometry with bends and depressions Friction Friction

Geometry Simplifications 2-Dimensional 2-Dimensional Symmetric Symmetric Deformation from Circle to Square Deformation from Circle to Square Rigid Target Surface Rigid Target Surface Constant Thickness 1.6mm Constant Thickness 1.6mm

Governing Equation Hoop Stress Hoop Stress

Material Property Simplifications Isotropic Expansion Isotropic Expansion Non-Linear Non-Linear –Experimental tensile test data –20 points Coloumb Friction Effects Coloumb Friction Effects No strain rate effects No strain rate effects

Model Creation Element Type Element Type –Plane 42 4 noded 4 noded 2-Dimensional 2-Dimensional Non-Linear Non-Linear Options Options –Plane Stress Option –Local Coordinate System –Extra Shape Functions

Meshing Hydro-Form Die Hydro-Form Die –Rigid Target No mesh allowed No mesh allowed Hydro-Form Blank Hydro-Form Blank –Mapped Mesh Angled Angled Thickness split Thickness split

Contact Elements Allows modeling of contact between two objects Allows modeling of contact between two objects Used Contact Wizard Used Contact Wizard –Rigid Target –Deformable Contact –No Separation (sliding) option –Coloumb Friction (0.27)

Solution Control Options Static Static –Quasi-Static Evaluation Non-Linear Solution Non-Linear Solution Stepped Loading Stepped Loading Auto Time Steps Auto Time Steps

Constraints Target Die Target Die –Fully constrained –Cannot Move Contact Blank Contact Blank –Symmetrically Constrained

Load Steps Using a simple “do” loop Using a simple “do” loop –Slowly increase internal pressure –380 MPa Used second “do” loop Used second “do” loop –Maintain pressure for a period of time Repeated for different meshing configurations Repeated for different meshing configurations

Findings Difference between 90 elements and 1400 elements was 0.032mm Difference between 90 elements and 1400 elements was 0.032mm 0.3% difference 0.3% difference Close to general manufacturing machining tolerances Close to general manufacturing machining tolerances

Continued Work Refine Finite Element simulation to match real world parts Refine Finite Element simulation to match real world parts –3-Dimentions –Different materials –Different deformation shapes Stress State analysis Stress State analysis

Conclusion and Thoughts The Finite Element Method and Ansys seem to be appropriate for analyzing this problem The Finite Element Method and Ansys seem to be appropriate for analyzing this problem Model seemed as respond well with about 100 elements Model seemed as respond well with about 100 elements