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© 2008 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary
2008 International ANSYS Conference
Evaluation of Current Density Temperature and Deformations in Sheet Metal Strip and Dome Height Tests
Amir Khalilollahi, David Johnson, John RothPenn State - Erie
© 2008 ANSYS, Inc. All rights reserved. 2 ANSYS, Inc. Proprietary
Introduction
• Applying a direct current to a workpiece during deformation dramatically improves the workability of the metal, without many of the drawbacks of seen with traditional manufacturing processes such as cost, undesired material property changes, etc.
• Since this previous research only utilized simple uniaxial workpieces, focus is now being turned on to more common and complex 3-D geometries that are seen in industry.
© 2008 ANSYS, Inc. All rights reserved. 3 ANSYS, Inc. Proprietary
Objectives
• To investigate how the current flows through these more complex 3-D geometries and determine if the flow field can be manipulated.
• To se Finite Element Analysis (FEA) to generate a model that can be used to simulate the effects of current flowing through the work piece by determining the temperature and current density profiles.
© 2008 ANSYS, Inc. All rights reserved. 4 ANSYS, Inc. Proprietary
Goals
• To compare to experimental results to show a relationship between the temperature profile and the current density distribution.
• To vary the parameters of the model to determine if the current density distribution can be modeled.
• To initiate multi-field FE models to evaluate thermal/structural deformation and stress values in two sheet metal specimens.
© 2008 ANSYS, Inc. All rights reserved. 5 ANSYS, Inc. Proprietary
FE Models
• Dome Modeling CAD-FE Models
Experimental Setup
© 2008 ANSYS, Inc. All rights reserved. 6 ANSYS, Inc. Proprietary
FE Models
• FE Models are helpful in determining…
– Effect of the clamps on the current flow and heat transfer– Effect of contact resistances between workpiece and
electrode– Effect of convective heat transfer on the temperature
distribution– Material properties and the temperature dependence of
the material properties– Evaluation of stress/deformation
© 2008 ANSYS, Inc. All rights reserved. 7 ANSYS, Inc. Proprietary
Results (Dome Model)
• Thermoelectric Models– Parameters were altered in the model to determine if
the change affected the temperature and current density distributions.
– Setup 1: Overall Effect of Applying Current– Setup 2: Effect of Duration of Current– Setup 3: Effect of Amount of Current– Setup 4: Effect of Clamping Locations– Setup 5: Effect of Dome Geometry -Height
© 2008 ANSYS, Inc. All rights reserved. 8 ANSYS, Inc. Proprietary
Temperature and Current DensityLocation: Corner to Corner
TEMPERATURE• Location: Corner to Corner• Current: 1635 A• Time: 15 sec
CURRENT DENSITY
323°C
Actual Max. Temperature 340°CPredicted Max. Temperature 323°C
© 2008 ANSYS, Inc. All rights reserved. 9 ANSYS, Inc. Proprietary
Temperature and Current DensityLocation: Corner to Side
TEMPERATURE• Location: Corner to Side• Current: 1655 A• Time: 15 sec
CURRENT DENSITY
323°C
Actual Max. Temperature 344°CPredicted Max. Temperature 334°C
© 2008 ANSYS, Inc. All rights reserved. 10 ANSYS, Inc. Proprietary
Temperature and Current Density Location: Adjacent Sides
TEMPERATURE• Location: Adjacent sides• Current: 1655 A• Time: 15 sec
CURRENT DENSITY
Actual Max. Temperature 226°CPredicted Max. Temperature 235°C
© 2008 ANSYS, Inc. All rights reserved. 11 ANSYS, Inc. Proprietary
Experimental Thermal Image
Typical thermal image of dome using FLIR imaging camera (ThermoVision A20m)
© 2008 ANSYS, Inc. All rights reserved. 12 ANSYS, Inc. Proprietary
Results (Dome Model)
• Summary– Parameters were altered in the model to determine if the
change affected the temperature and current density distributions.
– Model produces accurate temperature distributions that match up well with experimental results
– Model shows relationship between the temperature profile and the current density distribution.
– Model shows that as the various parameters are changed, the resulting temperature and current density distributions are also affected.
– By manipulating certain parameters, the flow field of current can be moved to areas of the workpiece that may be prone to failure. By increasing the current density in these areas, the workability is improved and failure is delayed.
© 2008 ANSYS, Inc. All rights reserved. 13 ANSYS, Inc. Proprietary
Load Step 1
• Structural Model– Solid bodies are meshed with
SOLID185 (sheetmetal plate)– SOLID186 for clamp rings and
hemisphere-shaped tool– CONTA174 and TARGE170
are used for contact – 0.25 coefficient of friction was
used
Load Step 1: clamp rings are tightened (5 mm) to firmly hold the plate
© 2008 ANSYS, Inc. All rights reserved. 14 ANSYS, Inc. Proprietary
Load Step 2
Load Step 2: Indenter fully engaged; dome is formed. Von Misesstress values shown
Indenter
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Load Step 3
Load Step 3: Indenter is lowered to original position; residual stresses in dome
© 2008 ANSYS, Inc. All rights reserved. 16 ANSYS, Inc. Proprietary
FE Strip Model
• SOLID186 for structural analysis • SOLID226 with TEMP and VOLT
DOF for the thermal-electric simulation
• CONTA174 and TARGE170 are used for contact
• 0.2 coefficient of friction for structural analysis,
• thermal contact conductance, but no electrical contact conductance
• The aluminum plate is 0.94 mm thick, 50.8 mm wide, and 277.8 mm long
© 2008 ANSYS, Inc. All rights reserved. 17 ANSYS, Inc. Proprietary
Loading steps
• Initially the punch in brought into contact with the aluminum plate, with a load of 3 N
• Thermal-electric transient analysis is performed for a duration of 0.5 sec with 2000 Amps DC
• The transient is halted at 0.5 seconds and the static structural analysis is updated with the temperatures developed by resistive heating
• The punch descends into the aluminum plate at a rate of 25.4 mm/minute for the same time interval of 0.5 seconds
• The geometry is updated from the static structural analysis deformations and the next (0.5 second) transient simulation is performed
• This alternating looping continues updating each model every 0.5 seconds for 120 steps, (60 sec) of elapsed time
© 2008 ANSYS, Inc. All rights reserved. 18 ANSYS, Inc. Proprietary
Temperature
Temperature distribution at 60 s
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von Mises Stress
von Mises stress distribution at 60 s
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Summary
– The structural FE modeling presented is work in progress mostly due to the needed updates in experimental setup
– ANSYS can be used to predict the effects of important parameters in the sheet metal fabrication, and in conjunction with the effect of electrical current on workability and joule heating effects
– The present work has shown that it is feasible to develop a detailed coupled multi-field non-linear FE model that incorporates a looping script to sequentially solve for electrical/thermal/structural fields
– This would offer determinations of deformations and stresses that are realistic in sheet metal manufacturing process