2008 International ANSYS Conference · © 2008 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary 2008 International ANSYS Conference Evaluation of Current Density Temperature

© 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


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.


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.


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.


FE Models

• Dome Modeling CAD-FE Models

Experimental Setup


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


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


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


Temperature and Current DensityLocation: Corner to Side

TEMPERATURE• Location: Corner to Side• Current: 1655 A• Time: 15 sec

CURRENT DENSITY

323°C



Temperature and Current Density Location: Adjacent Sides

TEMPERATURE• Location: Adjacent sides• Current: 1655 A• Time: 15 sec

CURRENT DENSITY



Experimental Thermal Image

Typical thermal image of dome using FLIR imaging camera (ThermoVision A20m)


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.


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


Load Step 2

Load Step 2: Indenter fully engaged; dome is formed. Von Misesstress values shown

Indenter


Load Step 3

Load Step 3: Indenter is lowered to original position; residual stresses in dome


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


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


Temperature

Temperature distribution at 60 s


von Mises Stress

von Mises stress distribution at 60 s


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

Documents

2008 International ANSYS Conference · © 2008 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary 2008 International ANSYS Conference Evaluation of Current Density Temperature