Workshop 2. Simulate the Crushing of an Empty Soda Can

Workshop 2

Simulate the Crushing of an Empty Soda Can

ANSYS Explicit Dynamics

ANSYS, Inc. Proprietary

© 2009 ANSYS, Inc. All rights reserved.

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Workshop 2. Simulate the Crushing of an Empty Soda Can

Workshop Goal and Procedure

Goal:

Crush an aluminum beverage can and allow it to “springback”

Procedure:

Create an Explicit Dynamics (ANSYS) Analysis System Project

Select the units system and define the material properties

Import, modify, and mesh the soda can geometry

Define analysis settings, boundary conditions, and external loads

Initiate the solution (AUTODYN - STR) and review the results

Training Manual



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Step 1 – Create the Project Schematic

Training Manual

Start ANSYS Workbench and follow the sequenced steps using the abbreviations shown below:

– DC = Double Click with Left Mouse Button

– SC = Single Click with Left Mouse Button

– RMB = Right Mouse Button Selection

– D&D = Drag and Drop = Hold Left Mouse Button down on item while dragging it to new location and then release it (i.e., Copy or Move)

1. Create an ANSYS Explicit Dynamics Analysis System Project

DC



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Step 2 – Specify the Project Units

Training Manual

2.a Select MKS for the Project Units from the Units List provided

2.b Request that Native Applications

in Workbench have their values be

Displayed in the Project Units

2.c Check those unit systems to

Suppress from appearing in the

Units List

Note:

Engineering

Data is native in Workbench, but Mechanical is NOT at this time (but will be in the future).



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Step 3 – Define Engineering Data Material

Training Manual

3.a Edit the Engineering Data cell to add a material to the default library.

DC

3.b Select the last slot under Engineering

Data to define a new material model.

Note: An existing material model in the Explicit

Materials library could have been selected, but there are restrictions on element types that can be used with certain material models, which will be discussed later.

3.c Enter material model name:

“ My_Aluminum ”

SC



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Step 3 – Define Engineering Data Material ...

Training Manual

3.d Make sure the new material is active in order to define its properties

DC

DC

SC

3.e Add the following Physical Properties to the material definition:

– Density

– Isotropic Elasticity

– Bilinear Isotropic Hardening

DC



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Training Manual

3.f Enter the following values:

Density = 2710 kg m^-3

Young’s Modulus = 7e10 Pa

Poisson’s Ratio = 0.30

Yield Strength = 2.9e8

Pa

Tangent Modulus = 0.0

Pa

Since the material is sufficiently defined, the blue question marks and yellow fields are no longer present in the data table.



Note: The resulting stress-strain curve is elastic – perfectly plastic. No strain hardening can develop.

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3.g Return to the Project Schematic

3.h Save the Project by selecting the

“Save As ...” icon and Browse to the directory indicated by your instructor.

Use the name “ empty_soda_can ” for the Project name.

Training Manual

Note: Saving the

Project saves all of the important files.

The Project may also be Archived, in which all of the supporting files are compressed and saved in one file.



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Step 4 – Import and Modify the Geometry

Training Manual

4.a Import the geometry by the procedure shown.

Do NOT Double Click on the “Geometry” cell ...

RMB

SC

4.b Browse to the DesignModeler

11.0 SP1 geometry file named:

“ soda_can_filled_110.agdb

”

4.c Workbench has now identified the geometry file (note green checkmark in Geometry cell). It is now OK to Double Click on

“Geometry”, as the new default action is to Edit the geometry.

Default actions are shown in bold type after RMB selects.



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RMB

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Step 4 – Import and Modify the Geometry ...

4.d Suppress the solid “Soda” and the surface body “Hole”.

Training Manual

4.e Generate the changes in the geometry. Although additional modifications could be made, but none are needed.

4.f Save the entire

Project via the DM

“Save” icon.

RMB

SC



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Step 5 – Edit the Model in Mechanical

5.a Edit the model in Workbench Mechanical.

RMB

Training Manual

Since Edit is the default action, double-clicking on the Model cell is also acceptable here.

SC

5.b Select the MKS Units system

– Recall that Mechanical is not native in Workbench, so the Units here may not match the Project Units

Note: Although the unit system used for data entry and post-processing is the MKS system, the actual unit system used by the AUTODYN solver is the mm-mg-ms system, because it provides higher accuracy. This will be shown later when the

Analysis Settings are discussed.



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Step 5 – Edit the Model in Mechanical ...

Training Manual

5.c Define the Aluminum Can properties:

– Stiffness Behavior = Flexible

– Thickness = 0.00025

meters

– Material Assignment = My_Aluminum

5.d Define the Punch and Die properties:

– Stiffness Behavior = Rigid

– Material Assignment = Structural Steel



Rigid Steel Punch

(moved downwards)

Flexible Aluminum

Soda Can (crushed)

Rigid Steel Die (fixed)

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Step 5 – Edit the Model in Mechanical ...

5.e Review the Contact specifications

Training Manual

Keep contact definition defaults

5.f Save the Project



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Note: There is no Save icon in Mechanical

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Step 6 – Set Sizing Controls and Mesh Model

Training Manual

6.a Select the Mesh branch

6.b Specify the Mesh Details:

– Physics Preference = Explicit

– Element Size = 0.010

meters

6.c Choose the Edge selection filter

6.d Orient the model to select the 8 edges that define the can circumferences (with the Left Mouse Button). Use the Ctrl key for multiple selections, as needed.

RMB

(anywhere)

SC SC

6.e With the 8 edges still highlighted,

Insert (RMB anywhere on graphics screen) an Edge Sizing



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Step 6 – Set Sizing Controls and Mesh Model ...

6.f Specify the Edge Sizing Details:

– Type = Number of Divisions

– Number of Divisions = 36

– Behavior = Hard

6.g Generate the Mesh (RMB on either

Mesh branch or Edge Sizing branch)

Training Manual

RMB

SC



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Mesh view

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Step 7 – Define the Analysis Settings

SC

Training Manual

7.a Specify the Analysis Settings:

– End Time = 6.0e-4 seconds

– Automatic Mass Scaling = Yes

– Minimum CFL Time Step = 1.0e-7 sec



7.b Set the Solve Units = mm, mg, ms

Note:

The mm, mg, ms unit system is the most accurate in most simulations, so it is the only one currently available.

Although more solver unit systems will be available in the future, any unit system in the drop-down list may be used to enter data and/or display the results.

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Step 7 – Define the Analysis Settings ...

Training Manual

7.c Keep the remaining defaults

Note:

There are multiple ways to control the erosion of an element. In this case, the element will only fail when the geometric strain reaches

150%.



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7.d Use the default number of data sets to save during the solution. Depending on the analysis, this number may need to be increased, but that requires additional disk space, so be judicious here.

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Step 8 – Apply BCs and External Loads

Training Manual

RMB

SC



SC

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8.a Fix the Steel Die (base):

– Select the Body filter

– Insert a Fixed Support under Explicit Dynamics

– Select the steel die

– Apply the selection

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Step 8 – Apply BCs and External Loads ...

RMB

SC

Training Manual

SC



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8.b Displace the Steel Punch

– Insert a Displacement under Explicit Dynamics

– Select the steel die

– Apply the selection

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Step 8 – Apply BCs and External Loads ...

Training Manual

8.c Specify the vertical (Y) displacement to be a Tabular load and set both the X and Z displacements to be zero.

8.d Ramp the Y displacement as follows:

Time = 0.0 sec Y = 0.0 meters

Time = 5e-4 sec Y = -0.060 meters

Time = 6e-4 sec Y = -0.030 meters

Note: The punch speed and abrupt change in direction are unrealistic, but sufficient for demonstration purposes. Normally, the movement would be prescribed according to a SINE wave function.



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Step 9 – Insert Result Items to Postprocess

Training Manual

9.a Insert a Total

Deformation plot request under the

Solution branch.

RMB

SC

SC

SC

RMB

SC

SC SC

9.b Insert an Equivalent

(von-Mises) Stress plot request under the Solution branch.

The rigid bodies (i.e., the punch and die) will not show stress.



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Step 9 – Insert Result Items to Postprocess ...

RMB

SC

SC

Training Manual

9.c Insert an Equivalent Plastic Strain plot request under the Solution branch.

9.d Save the

Project again.

Note:

SC

Even though a single time point (at the end of the run) is specified, the complete set of results can be viewed, including animations.

Recall that the default output controls (20 equally spaced time points) was retained under the Analysis Settings branch.



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Step 10 – Run the AUTODYN Simulation

SC

Training Manual

10.a Select Solver Output under Solution

Information and Solve the simulation.

The Solver Output shows the run statistics, including the estimated clock time to completion. Any errors or warnings are also noted.

Termination due to “wrapup time reached” is expected here.



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Step 10 – Run the AUTODYN Simulation ...

10.b Select Energy Summary under Solution

Information to review the global statistics.

Note the abrupt changes in kinetic energy due to the unrealistic loading scenario ...

Training Manual

TIME = 5.0e-4 seconds occurs around 3200 cycles into run

Constant velocity after starting from rest



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Step 11 – Review the Results

Training Manual

11.a Select Total Deformation and Show the Elements under True

Scale. The maximum deformation (-0.060 m) exceeds the punch value due to the momentum involved (i.e., an excessive punch speed was used to reduce the required computer run time).



SC

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Step 11 – Review the Results ...

Training Manual

11.b Animate the results by setting the controls as shown below and then pressing the Animation button. For transient dynamics, the default Distributed mode is inadequate, as it linearly interpolates between saved results. The Result Sets mode is optimal, as it uses the actual saved data. To review a static result, just click on the desired Time or Value from the Tabular Data and use the RMB to pick Retrieve This Result. The given state will then be shown.

Pick these 2 first

Then pick this

Pick this to save the animation

To retrieve a given result ...



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RMB

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SC

Training Manual

11.c Repeat the procedure, if desired, for the von-Mises equivalent stress results.



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Note:

No stress can develop in a rigid body. The punch and die are each condensed out to a mass at their respective centers of gravity with six

DOFs active.

Contact is based on the exterior surface, so a six DOF body can have a complicated contact surface.

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Training Manual

SC

11.d Repeat the procedure one last time for the equivalent plastic strain results.

11.e. Hide the Punch and Die for a better view of the results. Per the Analysis Settings, erosion does not occur until the geometric strain is 1.50

RMB



SC

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Step 12 – Review the Output Files

Training Manual

12.a Pick Files under the View menu to access the Project files

12.b Select Open Containing Folder via the RMB option for the AUTODYN print file (admodel.prt).



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RMB

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Step 12 – Review the Output Files ...

12.c Double click on the file admodel.prt

Training Manual



12.d As noted earlier, the solver units system was mm-mg-ms in order to maximize the accuracy.

After the Simulation is done, the results are converted back into the current Mechanical units system.

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Training Manual

12.e The AUTODYN print file also contains the

Material Summary information and run statistics.

The Energy and

Momentum are shown on both a material basis and a Part basis

(shown here).



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Training Manual

12.f The Energy and Momentum Balance, Mass Scaling, and Run Times are also included in the admodel.prt file.



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12.g No mass was added to the model, since the time steps were all above the Minimum

CFL Time Step of 1.0e-7 sec set in Step 7.a under Analysis

Settings

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Training Manual

12.h Close the admodel.prt file and review the setup.log file in the same directory ( F:\exp_dyn\soda_can\empty_soda_can_files\dp0\SYS\MECH ).



12.i The setup.log file contains the information pertaining to the transfer of data from the

Explicit Dynamics (ANSYS)

Analysis System to the

AUTODYN Cycle Zero file, which is then run by the

AUTODYN solver.

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12.j Close the file and return to the Mechanical window (i.e., view the model itself again).

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Step 13 – Generate a Report

Training Manual

13.a Click on the Solution branch in the Project tree and then click on the Report Preview tab at the bottom of graphics window. ANSYS does the rest! It will now automatically generate a report by going through the entire tree and summarizing the model and the results.



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Step 13 – Generate a Report ...

13.b The model properties are summarized, including volume, mass, centroid, and moment of inertia properties.

Training Manual

13.c Loading information is also shown in clear table format.



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Training Manual

13.d Even the energy plots are conveniently assembled into the report.



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13.e The results data is shown.

13.f Finally, SAVE the model and exit ANSYS.

Training Manual



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Workshop 2. Simulate the Crushing of an Empty Soda Can

ANSYS Explicit Dynamics

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ANSYS Explicit Dynamics

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