Modelling and Simulation for dent/deformation removal

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• Modelling and Simulation for dent/deformation
  removal
• Henry Tan
• Tuesday, 24/2/09

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Collapse of a Plate
r radius of collapsed area R radius of the
pressurized area h thickness
r
R
pressure p
collapsed area
Collapse refers to loss of the load-carrying
capacity of a component
Material regarded as rigid/perfect plastic
Critical pulling pressure to cause plate collapse
Critical pulling force to generate collapse
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Rigid / Perfect-Plastic Material
elastic/linear-hardening
rigid/perfect plastic
Test data for a steel
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Sample 1 Twist-A-Dent
Ads from Ding King Dent Repair Tool
Twist the turning knob until the dent pops.
pulling bridge
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Sample 1 Calculations
Yield stress
Thickness h 1.5mm
Force needed to generate plastic collapse
Radius of pulling bridge support
Pressure on the bridge support during collapsing
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Sample 2 Pulling
Vacuum pressure to lift the dent to it's normal
position
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Sample 2 Force Balance of the Puller
Pumping force
Pulling force
Pressure exerted by the dent to the puller
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Finite Element Method Elements and Nodes
Meshing to create elements and nodes Nodes to
save information Element to Interpolate
information
Tetrahedron element
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System Equations Establishing and Solving
Build up system equations Approach 1 Force
balance equations for each node Approach 2
Minimize the potential energy of the system
Solving equations nonlinear equations
(involving plasticity)
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FEM Output for Design
Output (deformation field, stress field)
Using output for design guidance
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As a FEM User
Inputs for FEM processing (pre-processing)
2. Materials
1. Geometry
4. Load (increasing)
3. Boundary conditions
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Initial Residual Stresses, Damaged Material
Initial residual stresses and damaged material
properties are unknown. Denting process needed
to generate the stresses and materials before
pulling. Dynamic denting (compared with static
pulling/recovering) needs to be considered.