ansys_ls-dyna cd book - ansys, inc

8/22/2019 Ansys_ls-dyna CD Book - Ansys, Inc

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Exercise 2: PDA Drop Test - 1 -

Exercise 2: PDA Drop Test.

In this exercise, we will perform a drop test of a typical personal digital assistant(PDA) electronic device. Mobile electronic devices are becoming increasingly

more popular, and the ability of the devices to sustain an impact after beingdropped is important. The PDA used in this analysis is illustrated in the figurebelow. The goal of this analysis is to determine if the case will break or thebatteries (C) will be ejected from the device should it suffer a six foot drop onto arigid surface.

A: Glass Touch Screen B: Battery Compartment C: Batteries

We will start this exercise with a predefined ANSYS database containing thegeometry of the PDA device. This geometry could be imported from anycommercial CAD program using a variety of ANSYS translators supporting allmajor geometry formats.


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Summary of steps:

1. Launch ANSYS/Multiphysics/LS-DYNA:

1.1. Launch ANSYS using your start menu.

2. Setup:

2.1. Resume database.

2.2. Plot model

2.3. Plotting Controls

2.4. Set preferences to Structural LS-Dyna

3. Modeling:

3.1. Element Type Definition

3.2. Real Constants

4. Material Properties:

4.1. Case Material Properties

4.2. LCD Material Properties

4.3. Battery Material Properties

5. Model Attributes:

5.1. Case Attributes

5.2. LCD Screen Attributes

5.3. Battery Cover Attributes

5.4. Battery Attributes

6. Meshing:

6.1. Mesh Batteries

6.2. Mesh PDA

7. LS-Dyna Options:

7.1. Contact Definition

8. Drop Test

8.1. Drop Test Input9. Solution:

9.1. Save Model

9.2. Perform LS-Dyna Solution


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10. Post Processing:

10.1. Report Generation

10.2. Von Mises strain animation10.3. Determine max stress in PDA.

10.4. Determine max stress in LCD display.

10.5. Report Assembly

11. Conclusions:

11.1. Examine Stress and Strain Values

11.2. Exit ANSYS.


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1.1.B 1.1.A

1.1.D

1.1.C

Step-by-step Instructions:

Before beginning this problem, create a separate folder on your computer for this

job and copy the ANSYS database pda.db to this folder. This file is located onCD 1 in a folder called Input Files.

1. Launch ANSYS/LS-Dyna

1.1. Launch ANSYS using your start menu.

A. Browse to select the working directory you just created for this job.

B. Enter a job name (pda1). All ANSYS files created for this problem willhave a filename of pda1 allowed by a unique extension.

C. Change the workspace and database sizes for this job to be 512 and

128 respectively.D. Click RUN to start the ANSYS GUI.


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2.1.A

2.1.B

2.1.C

2.1.D

2. Setup

2.1. Resume database.

A. We will start with an ANSYS database thats already been created for

you. This database contains only the geometry of the PDA. In theANSYS utility menu, pick File

B. Resume from

C. Pick the file pda.db which you should have copied to the workingfolder from the CD.

D. OK.

E. The model will be loaded into ANSYS and plotted in the graphicswindow. Note that by default, ANSYS plots only the solid entities orvolumes. For our model, the batteries are the only solid entities. The

PDA device will be modeled with shells or areas.


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2.1.E

Only batteries are shown


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2.2.A

2.2.B

2.2. Plot Model

A. In order to view the entire model, we must plot areas. In the ANSYSUtility Menu, pick Plot

B. Areas


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2.3.A

2.3.B

2.4.C

2.3. Plotting Controls

A. Use the Pan/Zoom/Rotate function to scrutinize all parts of the model.In the utility menu, pick PlotCtrls

B. Pan, Zoom, Rotate A view control window will appear on yourscreen.

C. You may want to keep this window active at all times.


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These buttons will orient yourdisplay to predefined viewperspectives.Zoom by picking a center

point and the edge of yourwindow.

Zoom by picking twodiagonal corners of your

window.

Arrows will pan your model inthe direction of the arrow.The distance your model is

moved can be controlledusing the Rate slider below.

Rotate buttons willincrementally rotate yourmodel about the screen axisand direction shown on thebutton. The amount ofrotation is also controlled by

the rate slider.

Activate dynamic mode.With this button checked,you can use dynamic viewingcontrols.

Use the left mouse button topan the model.

With the middle buttondepressed, move up/down tozoom in/out, and left/right torotate about the screen Z-axis.

With the right buttondepressed, move up/down torotate about the screen X-axis, and left/right to rotateabout the screen Y-axis.

With dynamic Modechecked, you can use themouse buttons described atleft to move the model or thelights used in light sourceshading.

The Fit button will scale yourmodel to fit in the window.


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2.4.A

2.4.C

2.4.B

2.4. Set preferences to Structural LS-Dyna

A. In the ANSYS main menu, pick Preferences

B. Pick the button that says LS-Dyna Explicit. Note: Your menu maylook slightly different depending on which ANSYS products you havelicensed.

C. OK. This filters the menu system to show you commands used forexplicit analysis only.


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3.1.A 3.1.B

3. Modeling:

In this section we will perform all the model definition, which includes definingelement types, materials, real constants, meshing and creating contact pairs.

3.1. Element Type Definition

For this analysis, we will use two element types. A shell element will be used forthe case, LCD screen, and battery cover. The batteries will be meshed with solidbrick elements.

A. In the Prepcessor menu, pick Element Type

B. Add/Edit/Delete


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3.1.C

3.1.D

3.1.E

3.1.F

C. Add

D. Pick Thin Shell 163

E. The Element type reference number is set to 1.

F. Apply.


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3.1.G

3.1.J

3.1.H

3.1.I

G. Pick 3D Solid 164.

H. Element type reference number2 should be predefined for you.

I. OK.

J. The two element types you just defined should be listed in the ElementTypes dialog. Pick Close.


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3.2.A

3.2. Real Constants:

Some element types require additional properties to be defined, which are notinherent in their basic definition such as thicknesses. Real constants are used to

define these properties. The shell elements used for the case and LCD screenrequire a shear factor, number of out-of-plane integration points, and a thickness.We will assign a third real constant for the battery cover even though itsproperties are identical to the case. The reason for this will be discussed laterduring parts creation and contact definition.

A. In the Preprocessor menu, pick Real Constants


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3.2.B

3.2.C

3.2.D

B. Add.

C. Pick Type 1 SHELL163 as the type of real constant you want to define.

D. OK.


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3.2.E

3.2.F

3.2.G

3.2.H

E. Enter5/6 for the shear factor.

F. For No. of integration points, enter3.

G. For Thickness at node 1, enter0.5. This real constant will be used forthe case and battery cover. The remaining thicknesses will default tothis value.

H. OK.


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3.2.I

3.2.K

3.2.J

I. Set 1 should show up in the Real Constant Set list. Pick Add to addanother one.

J. Pick Type 1 SHELL163 again for the type of real constant to define.

K. OK.


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3.2.L

3.2.M

3.2.N

3.2.O

L. Enter5/6 for the shear factor.

M. For No. of Integration points, enter3.

N. This real constant will be used for the LCD screen. Enter a thickness of0.75.

O. OK.


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3.2.R

3.2.Q

3.2.P

P. Set 2 should show up in the Real Constant Set list. Pick Add to addthe battery cover real constant.

Q. Pick Type 1 SHELL163 again for the type of real constant to define.R. OK.


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3.2.S

3.2.T

3.2.U

3.2.V

S. Enter5/6 for the shear factor.

T. For No. of integration points, enter3.

U. For Thickness at node 1, enter0.5. This real constant will be used forthe case and battery cover. The remaining thicknesses will default tothis value.

V. OK.


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3.2.W

W. Close the Real Constants dialog.


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4.1.A 4.1.B

4. Material Properties:

We will define three material models for our PDA. Material 1 will be a bilinearkinematic hardening model for the Polyurethane case. Material 2 will be a

bilinear kinematic hardening model for the liquid crystal display. The thirdmaterial will be a linear elastic model for the batteries.

4.1. Case Material Model.

A. In the Preprocessor menu, pick Material Props.

B. Define MAT Model


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4.1.C

4.1.F

4.1.E

4.1.D

4.1.G

C. Pick Add.

D. The material ID number defaults to 1.

E. Pick Plasticity.

F. Bilinear Kinemat.

G. OK.


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4.1.H

4.1.I

4.1.J

4.1.J

4.1.K

4.1.M

H. A dialog will appear for you to enter the material properties. The unitsfor our model are mm-Kg-Mpa. Enter1.71e-9 for the density.

I. Enter17200 for Youngs Modulus.

J. Enter0.35 for the Poissons Ratio.

K. Enter228 for the Yield Stress.

L. Enter5000 for the Tangent Modulus.

M. OK.


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4.2.A

4.2.D

4.2.C

4.2.B

4.2.E

4.2. LCD Material Model:

A. Material 1 should appear in the Material Model list. Pick Add to addthe LCD material model.

B. Material ID number2 should be predefined for this model.

C. Pick Plasticity.

D. Bilinear Kinemat.

E. OK.


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4.2.F

4.2.G

4.2.H

4.2.I

4.2.J

4.2.K

F. A dialog will appear for you to enter the material properties. The unitsfor our model are mm-Kg-Mpa. Enter1.64e-9 for the density

G. Enter10500 for Youngs Modulus.

H. Enter0.30 for the Poissons Ratio.

I. Enter125 for the Yield Stress.

J. Enter1000 for the Tangent Modulus.

K. OK.


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4.3.A

4.3.C

4.3.D

4.3.B

4.3. Battery Material Properties

A. Pick Add again to add the battery material model.

B. Material ID number3 should be predefined for you.

C. Pick Linear Elastic.

D. OK.


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4.3.E

4.3.F

4.3.G

4.3.H

E. Enter6.1e-9 for density.

F. Enter70000 for Youngs Modulus.

G. Enter0.29 for Poissons Ratio.

H. OK.


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4.3.I

I. We have completed the material definition. Pick Close.


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5. Model Attributes

Before we mesh our model, we will assign material, real constant, and elementtype attributes to the geometry. These attributes will then be assigned to the

elements as the geometric entities are meshed. We will use the assignmentslisted in the table below:

Part Material ID Real Constant Element Type

Case 1 1 1

Screen 2 2 1

Battery Cover 1 3 1

Batteries 3 1 2

5.1. Case Attributes:

Since the case is the largest part of this model, the easiest way to do this will beto assign the case attributes to all areas in the model, then to individually assignattributes to the screen and battery cover. The batteries are the only volumes(solids) in the model, so we can easily assign attributes to them.


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5.1.A

5.1.B

A. In the Preprocessor menu, under Attributes- pick Define.

B. All Areas.


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5.1.F

5.1.E

5.1.D

5.1.C

5.2.A

C. Set the case material number to 1.

D. Set Real constant set number to 1.

E. Set Element type number to 1 SHELL163.

F. OK.

5.2. Screen Attributes:

A. Next we will do the screen. In the Define attributes dialog, pick PickedAreas.


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5.2.C

5.2.B

B. A dialog will appear for you to select thescreen area. You may need to use thepan/zoom/rotate function to orient your model

to the front. Pick the LCD screen area asshown below.

C. OK.


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5.2.G

5.2.F

5.2.E

5.2.D

D. Set the case material number to 2.

E. Set Real constant set number to 2.

F. Set Element type number to 1 SHELL163.

G. Apply.


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5.3.A

5.3.B

5.3.C

5.3. Battery Cover Attributes:

The Area Attributes picker dialog should still be activesince you picked Apply instead of OK above. Use the

pan/zoom/rotate function to orient the model so you cansee the bottom side of the PDA.

A. In the picker dialog, change the method ofpicking from single to loop. With this method,you can pick one area of the battery cover,and all additional areas connected to it willalso be selected.

B. Pick one area on the battery cover. When yourelease the mouse button, the three tabs onthe top and bottom edges of the cover should

also be selected.C. In the picker dialog, you should have a total of

4 areas selected. Pick OK.

Make sure these tabsare selected also.


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5.3.G

5.3.F

5.3.E

5.3.D

D. Set the case material number to 1.

E. Set Real constant set number to 3.

F. Set Element type number to 1 SHELL163.

G. OK.


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5.3.D

5.4.B

5.4. Battery Attributes:

A. Before we assign attributes to the batteries, lets plot them. In theUtilities menu, pick Plot.

B. Volumes.


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5.4.C

5.4.D

C. The batteries should be plotted as shown below:

D. In the define attributes dialog, pick All Volumes.


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5.4.H

5.4.G

5.4.F

5.4.E

E. Set the case material number to 3.

F. Set Real constant set number to 1.

G. Set Element type number to 2 SOLID164.

H. OK.


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6.1.A

6.1.B

6. Meshing:

6.1. Mesh Batteries:

A. In the Preprocessor menu, activate the MeshTool.

B. Next, we will set the global element size. Pick the Set button underSize Controls: Global


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6.1.C

6.1.D

C. We will use an element size of 5 mm. Enter5 for Element edge length.

D. OK.


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6.1.H

6.1.F

6.1.E

6.1.G

E. The Meshtool should already set to mesh Volumes.

F. For element shape, pick Hex.

G. Mesh.H. Pick All.


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6.1.I

I. ANSYS will mesh the volumes and plot them as shown below.

6.2. Mesh PDA:

Next, we will mesh the case, LDC display, and battery cover all at once. In orderto do this, we must select all the areas in the model except for those that makeup the batteries. This can be done easily using the powerful select logic within

ANSYS.

We will do this by selecting all areas that are attached to the batteries (volumes),then selecting the inverse of this set.


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6.2.A

6.2.C

6.2.B

A. In the Utilities Menu, pick Select.

B. Everything below.

C. Selected Volumes.


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6.2.D

6.2.E

D. In the Utility menu, pick Plot.

E. Areas.


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6.2.F

F. You should only see the areas that encompass the batteries.


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6.2.G

6.2.H

6.2.J

6.2.I

6.2.K

6.2.L

G. In the Utilities menu, pick Select.

H. Entities.

I. Areas.

J. Invert.

K. Pick the Replot button.

L. Pres the Cancel button to close the Select Entities dialog.


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6.2.M

M. The PDA areas should now be plotted in the graphics window.


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6.2.N

6.2.Q

6.2.P

6.2.O

N. We are now ready to mesh the PDA. In the Preprocessor, activate theMeshTool again.

O. Change Volumes to Areas.

P. For Shape, pick Free.

Q. Mesh.


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6.2.R

6.2.S

R. PickAll.

S. It may take a few minutes to mesh the PDA.ANSYS will plot the mesh in the graphics

window when finished.


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6.2.U

6.2.T

T. Lets verify that the attributes were set for the case, LCD display, andbattery cover as we desire. In the Utilities menu, pick PlotCtrls.

U. Numbering.


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6.2.X

6.2.W

6.2.V

V. For Elem / Attrib numbering, pick Real Const num.

W. Select Colors only for Numbering shown with.

X. OK.

Y. Use the pan/zoom/rotate function to view all sides of the model. TheLCD display and battery cover should be a different color from thecase.

As a separate exercise on your own, change the plot numbering to Material IDand replot the mesh. Use the select function to select the batteries and verifytheir attributes.


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6.2.Y


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7.1.A

7.1.B

7.1.C

7.1.D

7. LS-Dyna Options:

7.1. Contact Definition.

A. Before we proceed, lets make sure all entities are selected. In the

Utilities menu, pick Select.

B. Everything.

C. In LS-Dyna Parts are used to define contactbetween different components of a model. Wewill need to define parts in order to simulatecontact between the batteries, case and batterycover. .In the Preprocessor menu, pick LS-DYNA Options.

D. Parts Options.


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7.1.E

7.1.F

E. Create Parts should be highlighted. Pick OK.

F. ANSYS will create a part for each unique combination of material ID,real constant, and element type, and list these for you. Recall earlier

that we used a separate real constant for the battery cover eventhough it was the same as case. This was done to ensure that thebattery cover would be its own part. Otherwise, we could not definecontact between the battery cover and the case.


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7.1.H

7.1.I

G. Before you close the parts list window, make a note of the part IDnumbers and identify which component they refer to based on theattributes we defined earlier. It may be helpful to update the table in

section 5 of this demo and add a column for part ID. Create and printout a table like the one below:

Part Part ID Material ID Real Constant Element Type

Case 3 1 1 1

Screen 4 2 2 1

Battery Cover 2 1 3 1

Batteries 1 3 1 2

We are now ready to define contact between the various parts. We will definethree contact pairs:

Contact between the case (3) and batteries (1).

Contact between the case (3) and battery cover (2).

Contact between the battery cover (2) and batteries (1).

H. In the LS-Dyna Options menu, pick Contact.

I. DefineContact.


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7.1.J

7.1.K

7.1.L

7.1.M

7.1.N

7.1.O

J. In the Contact Parameter Definitions dialog, pick Nodes to Surface.

K. General (NTS).

L. For Static Friction Coefficient, enter0.2.

M. For Dynamic Friction Coefficient, enter0.1.

N. For Viscous Damping Coefficient, enter0.1.

O. Apply.


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7.1.P

7.1.Q

7.1.R

P. Pick 3 (case) for the Contact Part no.

Q. Pick 1 (batteries) for the Target Part no.

R. Apply.


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7.1.S

S. We will use the same contact options for the next pair also. Pick Applyin the Contact Parameters Definition dialog.


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7.1.T

7.1.U

7.1.V

T. Pick 3 (case) for the Contact Part no.

U. Pick 2 (battery cover) for the Target Part no.

V. Apply.


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7.1.W

W. We will use the same contact options for the last pair. Pick OK in theContact Parameters Definition dialog.


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7.1.X

7.1.Y

7.1.Z

X. Pick 2 (battery cover) for the Contact Part no.

Y. Pick 1 (batteries) for the Target Part no.

Z. Apply.


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8.1.A

8.1.B

8.1.C

8. Drop Test:

The ANSYS drop test module can greatly simplify the set up of a drop testanalysis. We will use it to perform the following functions:

Orient the model to its impact position.

Define G.

Define a drop height.

Automatically define a rigid impact surface and contact definitionbetween it and your model.

8.1. Drop Test Input:

A. First, we must enter the drop test module. In the ANSYS Main Menu,pick Drop Test Module.

B. Initialize.

C. OK.


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8.1.D

8.1.E 8.1.F

D. When the initialization procedure completes, your model will be plottedin the graphics window, with the default orientation for G shown in theupper left.

E. Pick the Orient Model button.

F. Several methods of orienting your model are available. We will use aninput vector method. Pick Input Vector.


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8.1.G

8.1.H

8.1.I

G. A dialog will appear for you to enter the x,y,z vector defining the verticaldirection. Enter3, 10, 5 as the vector components as shown below.

H. OK.

I. ANSYS will create a rigid target surface oriented using this vector, andposition it so that it is just about to impact the lowest portion of themodel. The graphics view will be oriented normal to drop direction.Note that your model hasnt been moved, only the view direction.


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8.1.J

8.1.K

J. Use the pan/zoom/rotate function to view how the model is oriented.Rotate the model 90 degrees about the screen Y-axis.

K. Next, we will define the units of gravity. In the Drop Test Module menu,pick Define g.


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8.1.L

8.1.M

8.1.N

L. Since our model is built in units of millimeters, pick 9810 mm/s^2.

M. OK.

N. In the Drop Test Menu, pick Drop Height.


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8.1.O

8.1.P

8.1.Q

O. Enter a value of1829 mm, which is approximately 6-feet. We will usethe default height reference point, which is the lowest point or impactpoint on the model.

P. OK. ANSYS will use the drop height and acceleration of gravity todetermine an initial velocity for the model. This way, the analysis canbegin at a point just prior to impact in order to save computation time.

Analyzing the free fall would be costly and unnecessary.

Q. Next, pick Solution Ctrls in the Drop Test Module menu.


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8.1.T

8.1.S

8.1.R

8.1.U

R. Enter a value of0.06 for the time.

S. We will use the default setting of100 for Result file output interval.

T. Change the Time-History output interval to 100.

U. OK.


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8.1.V

8.1.W

V. ANSYS will give you the option of calculating the node nearest to thecenter of gravity and saving time history data for this node. This maybe beneficial for post processing some problems. Close this Note.

W. Pick OK to calculate this node. This may take a few minutes.


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9.1.A

9.2.A

9.2.B

9. Solution:

We are ready to solve the problem.

9.1. Save model:A. In the Toolbar menu, pick SAVE_DB.

9.2. Perform LS_Dyna Solution:

A. In the Drop Test Module menu, pick Solve.

B. ANSYS will display the drop test information.Pick Close when you have finished reviewingthis note.


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9.2.C

C. Pick OK to solve the analysis. The solution may take several hours.


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10.1.C

10.1.B

10.1.A

10. Post Processing:

For this model, we will generate animations of the impact event over time, andalso plot the von mises stress in the PDA components. We will generate an

HTML report during the process.10.1. Report Generation.

A. In the ANSYS Main Menu, pick General PostProc.

B. In the Utility menu, pick File.

C. Report Generator.


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10.1.D

10.1.E

D. ANSYS will prompt you for a directory name to store the report files andwhether to append or overwrite an existing report. Accept the defaults

by picking OK.

E. ANSYS will prompt you to create a new directory. PickYes.

ANSYS will resize your graphics window so that subsequent screen captures thatare done for the report will properly sized for an HTML report. Also, a reportcreation wizard will appear as shown below.

Capture thecurrentscreen plotfor the report.

Generate ananimation.

Capturea listing

Capturea table.

Modifysettings

Assemble itemsinto a report.


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10.1.F

10.1.G

10.1.H

F. We will begin creating our report by generating animations of thedeformed results. First, lets set the deformed model scaling to truescaling. By default, ANSYS scales the deformed shape to equal 5% of

the model length. This is appropriate for small deflection analyses, butfor a drop test, we wish to see the true scaling. In the Utilities menu,pick PlotCtrls.

G. Style.

H. Displacement Scaling.


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10.1.I

10.1.J

I. Change t he Displacement scale factor to 1.0 (true Scale).

J. OK.


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10.1.K

10.1.L

K. In the General Postproc menu, pick Last Set to load the final resultsdataset into memory.

L. In the ANSYS Report Generation wizard, pick the video camera icon togenerate an animation.


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10.1.M

10.1.N

10.1.O

10.1.P

10.1.Q

10.1.R

M. In the Animation Capture dialog, select Over Time.

N. OK.

O. For Number of animation frames, enter50.

P. For display type, pick Stress.

Q. Von Mises SEQV.

R. OK. The animation generation may take several minutes to complete.


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10.2.A

10.1.S

S. When the animation is complete, the displaced results from the finaltime point will remain displayed in the graphics window. Note that the

battery cover has popped out and ejected the batteries.

10.2. Von Mises strain animation:

A. Next, pick the video camera again to generate another animation.


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10.2.B

10.2.C

B. We will use the same settings. Pick OK.

C. In the graphics window, use the pan/zoom rotate function to rotate themodel 90 degrees in the Y- direction. The view should look like theone below.


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10.2.F

10.2.E

10.2.D

D. This time we will animate the plastic strain. For display type, pickStrain-plastic.

E. vonMises EPPLEQV.

F. OK.


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10.2.G

G. A plot of the final time point will remain in the graphics window whenthe animation generation is complete.


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10.3.A

10.3.B

10.3.C

10.3. Determine Max Stress in PDA:

Next, we wish to determine the maximum stress in the PDA. This most likelyoccurs at or soon after the moment of impact. We will plot the Von Mises stressat the first few time points, to locate the worst condition.

A. In the General Postproc menu under Read Results- pick First Set.This will load the results of the first time point into memory.

B. Pick Plot Results.

C. Nodal Solution.


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10.3.F

10.3.E

10.3.D

D. Pick Stress.

E. Von Mises.

F. OK.


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10.3.G

G. The von Mises stress from the first time point will be plotted in thegraphics window. This is the moment just before impact, so it shouldhave zero stress.


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10.3.G10.3.H

H. Use the pan/zoom/rotate function to view the PDA from the front again.You will have to rotate 90 degrees about the +Y axis.


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10.3.I

10.3.J

10.3.K

I. In the General Postproc menu under ReadResults-, pick Next Set. Thjs will load resultsfrom the next time point into memory.

J. In the Utilities menu, pick Plot.

K. Replot.


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10.3.L

L. The Von Mises stress will be plotted. Note the maximum value shouldbe around 186 PSI.


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10.3.M

M. Repeat this procedure until the stress level starts to decrease, thenpick the Previous Set button in the General Postproc menu to returnto the maximum condition. In the example below, the maximum occurs

at the fourth time point with a stress level of322 PSI.Recall when we defined material properties that the yield stress for the casematerial is 128 PSI. The case clearly has yielded or broken.


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10.3.O

10.3.N

10.3.R

10.3.Q

10.3.P

N. Lets capture this image so that we can add it to our HTML report later.In the Utilities menu, pick File.

O. Report Generator.

P. Pick Capture Image.

Q. Enter a caption of PDAMaximum Stress.

R. OK.


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10.4.B

10.4.A

10.4.C

10.4.D

10.4.F

10.4.G

10.4.E

10.4. Determine max stress in LCD display:

Next we will select the elements of the LCD display only, and repeat the stressplotting procedure in order to determine the maximum stress in this component.

A. Recall that the LCD display referenced material ID number 2. We canselect the elements by that attribute. In the Utilities menu, pick Select.

B. Entities.

C. Elements.

D. By Attributes.

E. Material num.

F. Enter2 for Min,Max, Inc.

G. OK.


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10.4.H

10.4.I

10.4.J

H. In the General Postproc menu under Read Results- pick First Set.This will load the results of the first time point into memory.

I. Pick Plot Results.

J. Nodal Solution.


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10.4.M

10.4.L

10.4.K

K. Pick Stress.

L. Von Mises.

M. OK.


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10.4.N

N. Like before, the stress at the first time point should be zero.


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10.4.O

O. Repeat the procedure used for the entire model. Pick Next Set andPlot >Replot until you find the maximum condition. For our example,a maximum stress of 32 PSI occurred during the third time point.

Recall that the LCD material yield stress was 125 PSI, so the LCDdisplay should survive this impact.


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10.4.Q

10.4.P

10.4.T

10.4.S

10.4.R

P. Lets capture this image so that we can add it to our HTML report later.In the Utilities menu, pick File.

Q. Report Generator.

R. Pick Capture Image.

S. Enter a caption of LCDMaximum Stress.

T. OK.


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10.5.A

10.5. Report Assembly:

A. We are now ready to assembly these items into a simple HTML report.Pick the HTML Report Assembler button in the report generatorwizard.


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10.5.C

B. A new wizard will appear with options for assembling the HTML report.

Preview thereport in yourweb browser

Delete itemfrom thereport.

Move itemup or downin report.

Adds text to thereport.

Allows you toinsert any imagefile from yourhard drive.

Adds dynamicitems to thereport.

Adds pre-existingHTML code froma file.

Previouslycaptured images,tables, and liststhat are availablefor assembly.

Change thereport heading


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10.5.F

10.5.G

10.5.E

10.5.D

C. Lets begin by changing the report heading. Click the Report Headingbutton in the HTML Report Assembler wizard shown on the previouspage.

D. A dialog will appear for you to enter a Title, Author Name, andSubtitle. Enter anything you wish here. See below for an example.

E. OK.

F. The header will appear in the work area of the Wizard.

G. Next, pick the first animation in the Report Images list.


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10.5.H

10.5.J

10.5.I

H. This image will be added to the report underneath the heading.

I. The icon in the image list will gray out indicating that it has been addedto the report.

J. Pick the second animation to add it to the report.


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10.5.K

10.5.L

K. The second animation will be added to the report.

L. Pick the next image in the list. This is the PDA Maximum stress image.


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10.5.M

10.5.N

10.5.O

M. The maximum stress image will be added to the report.

N. Pick the Text button to add a description of this plot.

O. Enter some relevant text in the box that appears.


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10.5.P

10.5.Q

10.5.R

P. Pick the last image in the list to add it to the report.

Q. Pick the Text button to add some relevant text.

R. Enter a description of the LCD display plot.


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10.5.S

S. We have completed the report definition. Pick the eyeglasses in theReport assembler window to view your report.


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10.5.U

T. Your report should look like the one below. Pick the image below for asample report.


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10.5.U

U. You can add more items to this report, at a later date if you wish. Letsquit for now. Pick File >Save and close.


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11. Conclusions:

11.1. Lessons Leaned.

The analysis we performed shows that the PDA case has failed and that the

batteries popped out. The LCD display survived the impact though. What couldwe do to improve the design? Increasing the thickness of the case would addstrength and stiffness, but would also add weight and increase the cost.

What other analyses would be necessary to verify this design. We only analyzedone orientation. As a separate exercise, repeat this analysis using a differentorientation vector. What orientations might result in worse stresses on the case?What orientation might be worse for the LCD screen?

We dropped this PDA from an initially static condition. What if we applied aninitial rotation or additional velocity to the PDA?


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11.2.A

11.2.C

11.2.B

11.2. Exit ANSYS:

A. In the ANSYS toolbar, pick Quit.

B. Highlight Quit No Save?C. OK.

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