ANSYS Workbench Tutorial Release 14

Placed Features, Assembly

2-1

Chapter 2 Placed Features, Assembly

2-1

OVERVIEW

In this chapter we illustrate DesignModeler creation of features whose shape predetermined. Among these are

IS

+ Holes + Rounds + Chamfers + Patterns In addition to these topics, at the end of the chapter we illustrate simple assembly modeling in ANSYS DesignModeler.

2-2

INTRODUCTION

Feature-based solid modeling involves the creation of part models by combining various features. The features illustrated in Chapter I are sometimes called sketched features because they were based upon sketched cross sections we created. Sketched features can have virtually any shape we desire. The basic parts of Chapter I can also be called base features since we started from scratch each time and created a new part. We can add features to base features to create more complex parts. If these added features have predetermined shapes they are often called placed features because all we need to do is specify the size and location or placement of the new feature on an existing base feature.

�"'-----------Placed Features, Assembly

2-2

rusion created earlier with a hole, a round and The figure below shows the L-shaped Ext . which features can be added to a a chamfer added to it. This demonstrates the m:nn~ 10 ful parts with the shapes desired base feature in order to create more complicate an use for specific tasks. . The tutorials that follow illustrate how to add these placed features to the basic parts created in Chapter 1.

Figure 2-1 Extrusion with placed features.

2-3

TUTORIAL

2A - ADDING A HOLE TO THE EXTRUSION

Follow the steps below to cut a hole in the top face of the short leg of the Chapter extrusion.

1

Start ANSYS Workbench and reload the L-section Extrusion 1.

ANSYS > Workbench> the fi Ie name you chose)

DesignModeler Geometry> Browse>

TutoriallA

(or

Now save this file under a new name for this tutorial. 2.

File> Save As > Tutorial2A (or another name you select)

We want to create the h~le on the top surface of the short leg of the extrusion. We will create a new plane on which to place the circle that generates the hole.

3.

Selection Filter: Model Faces (3D)

4.

Click on the top surface of the short leg.

~

Placed Features, Assembly

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Tools

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2-3

Help

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Figure 2-2 Surface selected. 5.

Create> New Plane (from the top menu)

A new plane is added to the tree structure (Plane4 in this illustration; your plane number may be different) and an axis system is provided. $A

Geometry

Desl~nModeler

.. ~

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Figure 2-3 New plane is created.

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*"

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Placed Features,

2-4

Assembly

J ~~/ Generate

6.

Click Generate

7.

Select Plane4 > Then click on the Look at icon to view the Plane4

~7"rude &!eR''''''''

"Sweep ~ Skh/lolt

tf

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Figure 2-4 'Look at' new plane. We want to place a 10 mm diameter circular hole half way along the length of the 100 mm leg and 8 mm from the edge. 8.

Sketching>

Circle Draw a circle on the top face as shown in the figure below.

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Gr~s

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Figure 2-5 Circle sketch.

_ _ _ .. i 1

__..._ ..._ ...._ .._ ..._ .. _1........

Placed Features, Assembly

2-5

9.

Dimensions> Diameter - Place 03 as shown.

10.

Dimensions> Horizontal-

11.

Dimensions> Length - Place L2 as shown.

Place HI as shown.

Edit the dimension values to 10 rom, SO rom, and 8 rom as shown in the figure above. (The number attached to each dimension, the I in HI, is an internal numbering scheme and depends upon the sketching sequence. Your numbers may be different.) 12.

Modeling> Click on Sketch in the tree structure (Sketch2 in the figure)

13.

Extrude

14.

Operation>

~Extrude

Cut Material

(Remove material instead of adding it.) 15.

Type> Through All

(Cut completely through the thickness, through all.) q.

Details View

B Details

or Extrude2

Details View

B Details

or Extrude2

Extrude

Extrude2

Extrude

Extrude2

Base Object

Sketch2

Base Object

Sketch2

I-A-:dd""'-M-:at-er-:ia7"1 ""'-.-1 Operation F:;":"":"""-::'---l Add Material

1-=::"::='---1 Extent Type

o FD1, Depth (>0)

Imprint Faces Add Frozen

None (Normal)

Direction

Reversed r.,F::.:ix:::ed:;Depth (>0) Fixed

30 mm

L

As Thin/Surf ace?

No

As Thin/Surf ace?

Merge Topology?

Yes

I FDl,

Generate (to complete the feature.)

To Next

Target Bodies To Faces f:'M:::e'::rg::"e'::T'-op-07Io-gy"-:?:---1 To Surface

Figure 2-6 Extrude details.

16.

Cut Material

Direction Vector

1 :) Generate

The completed hole is shown in the next illustration.

•..., /

Placed Features, Assembly

2-6

Figure 2-7 Circular hole.

Keep this part in memory since we bave more work to do on it.

2-4

TUTORIAL 2B - ADDING A ROUND TO THE EXTRUSION

A gradual transition between surfaces is variously called a fillet, a round or a blend. DesignModeler uses the blend terminology, and a blend is a placed feature. In this tutorial we will place a fixed )tJmlO G~. USel"',r§" t;. 1llIr@@@L radius blend at the inside corner of the L where tbe top II surface ofthc hort leg meets the inside vertical surface. ;:'.-t>~"""~~~~~~-~~'-' '", .... ep

ave your part u ing a new name. I.

•

~SOns\.oft

DTmJ"'f"'.

\l>BIend·

File> Save As > Tutorial2B

Set the selection filter.

[@

2.

election Filter: Edges

J.

elect the inside edge ofthe part.

Figure 2-8 Select the edge. 4.

Create>

Fixed Radius Blend

~

Placed Features, Assembly

1

File

Create

Concept

Tools

2-7

View Help

*- New Plane

~ tJ· lID

Tree

~

@

rm rm ,g.

:) Generate

Extrude Revolve

:r;

+

liaExtrude

@. $. @. ~ ~Revolve

Graphics

tJ. Sweep

B

~

SWn/Loft

I!II Thin/Surface ~ ..

FIxed Radius Blend Variable Radius Blend

::::: Vertex Blend

~

Chamfer

~

Pattern

Skate ~

I DetalS.

•

Body Operation

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Boolean Slice

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Face Delete

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Point

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Figure 2-9 Selecting the blend option.

5.

Geometry> Apply

,

(Use the default 3 mm radius.)

Details

orFBlend

Fixed-Radius FDI, Geometry

) Generate

q.

Details View

8

Cenerate

1

'-,-

Blend

Radius (>0)

FBlendl 3mm I EdQe

--

-

Figure 2-10 The blend completed,

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Placed Features, Assembly

2-8 2-5

TUTORIAL

2C - ADDING A CHAMFER TO THE EXTRUSION

Creating the chamfer is pretty much like creating the blend.

1.

Save As > Tutorial2C (Save the part under a new name if you wish)

Create Concept ~

Tools

New Plane

I!ilJ Extrude

6Ie Revolve 2. 3.

Selection Filter: Edges

f~

~

Sweep

~

5I
D Thin/Surface

Select the top inside edge of the part.

7

4.

Create>

Y

Fixed Radius Blend

Chamfer

Variable Radius Blend

5.

Details of Chamfer>

Chamfer

Geometry> Apply

(Change the sizing to 2.5 mm.)

~

Pattern

~

Body Operation

Slice EJ Detail. of Chamfer 1 Chamfer

Chamfer!

Geometry

1 Edge

Type

Left-Right

Figure 2-11 Select chamfer

J ,; Generate

6.

Generate

7.

Save your work

Figure 2-12 The chamf

er completed.

~

Face Delete

~

Point

View

Placed Features, Assembly 2-6

2-9

TUTORIAL 2D - PATTERNS

Next we will use a pattern operation to create a solid model of circular plate with a symmetric bolt hole pattern. First extrude a circle to create a 50 mm diameter plate that is 10 mm in thickness as shown in the next figure. Start a new part file. 1.

Sketch a 50 mm diameter circle with center at the origin of the XYPlane. Click on the sketch then on Extrude and set the extrusion depth to be 10 mm. Click Generate to complete the base feature disk.

2.

Sketching> Dimensions> Display> check both Name and Value.

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....

............................. ·········..·······..·..·····1"·············..--.··

.

,

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Figure 2-13 Base feature disk.

3.

Create > New Plane Create a new plane for sketching on the top or bottom surface of the base disk

4.

Sketch an 8mm diameter circle on this plane. Dimension as shown in the next figure.

5.

Sketch an 18 mm line from the center of the base feature to the center of the small circle. Dimension as shown below. We'll use this line for angular reference.

6.

Locate the line with an angular dimension. Click first on the horizontal axis, then on the line. Drag to place the dimension as shown.

7.

Switch to Modeling. Select the sketch and then Extrude> Through All to create a hole.

Cut Material>

Placed Features, Assembly 2-10

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Figure 2-14 Placement of small hole.

8.

Add a 1 mm chamfer to the top edge of the 8 mm hole. See figure next page.

9.

Sketch a short line along the Z axis in the ZXPlane: Sketch3. We will use this for the pattern angular direction reference later. Tree Outline 8

GraphIcs

.tI~1 A: Geometry I±J ..

.

;:f.. XYPlane

8 ..;:f.. ZXPlane ..61 Sketch3 .. ;:f.. YZPlane Extrude!

l+} .. ~

8 ..;:f.. PlaneS

..61 Sketch2 [+

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Extrude2

l

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1 Part, ! Body

Sketching

Modeling

.................... ..-_-L-.....; __

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Figure 2·15 Create a line along the Z axis.

Placed Features, Assembly

2-11

@

10.

Click Selection Filter: Model Faces (3D)

11.

Select the inside surface of the hole; then Ctrl > Select the surface of the chamfer so both items will be in the pattern.

Figure 2-16 Select the chamfer and hole.

12.

Create> Pattern

13.

Geometry> Apply (in details of Pattern I.)

14.

Pattern Type> Circular

15.

Selection Filter: Edges

16.

Axis> Click on Sketch3 and select the short Z axis line> Apply

17.

Angle> Evenly Spaced

18.

Number of Copies> 6 (Creates 7 instances total.)

Placed Features,

2-12

EI "y~

Assembly

Tutorial2E

rtJ·,,*," XYPlane B,,*," 2xPIane

Cl

L......

Sketch3

,,*," Y2Plane $ "-f

1tI,,*,"

Extrude 1 PlaneS

~ .."{~

Extrude2

i·······.j

Chamfer 1

L.. ....Y"~

Pattern1

00.... Sketching

1 Part, ! Body Modeling

I

EI Details of Pattern! Pattern

Patternl

Pattern Type

Circular

Geometry

2 Faces Not selected

FD2, Angle

Evenly Spaced

FD3, Copies (>0) 1

Figure 2-17 Pattern parameters. J ') Generate

19. Click Generate.

The resulting hole pattern is shown next. The selected edge is used as the axis for determining the positive direction of incrementing the angular placement (taken according to the right-hand rule). !I-

Tree Out~ne B.t

*' .,61 *' .,61 .,*' .,lii!. .,61 *' .,61

A: Geometry

H .,

XYPlane Sketch!

-'1 .,

ZXPlane Sketch3

-:J

t-J ., -1.,

Y2P1ane Extrudel Sketch1 PlaneS Sketch2 Extrude2 Sketch2

.,61 .,' .,~ .t

Chamfer1 Pattern! 1 Part, 1 Body

.,

S"id

Sketching MOdeling

I

Figure 2-18 Circular pattern of chamfered h I o es.

--

----=.-- .

2-13

Placed Features, Assembly

Once again don't be surprised if the suffix numbers of the entities (Sketch, Extrude, etc) in your tree structures differ from those in the figures. Same with the lighting bolts indicating need for generation. Some experimentation with generation, views, etc. was conducted to obtain the figures presented here. If you have a problem, delete the problem object in the tree and start again. (The positive direction for incrementing the angular placement is along the selected edge according to the right-hand rule. Change Evenly Spaced to 35 degrees> 6 Copies and see what solid is produced.) Linear patterns are created using similar steps. The direction of the pattern can be along an existing edge or perpendicular to a surface.

2-7

TUTORIAL 2E - CLEVIS ASSEMBLY

The next figure shows an assembly model of the clevis device that is the subject of this final tutorial in this chapter.

Figure 2-19 Clevis assembly.

1.

Start DesignModeler, Select Inches Units, and start sketching on the XYPlane

The yoke is 4.5 inches in overall length, 2.5 inches at its widest point, and the opening is 2.0 inches in width. Use the sketching tools to create the figure shown next with dimensions as indicated. Arc by Tangent, Modify> Trim, and other tools will come in handy. If you make a mistake, just delete the item in question and redraw, or just start over.

Placed Features, Assembly

2-14

0.125

0.125 RO.500

RO.500

···:t ······························t 0.250

.11....,..~~~~4

---.-1 0.250

j

~

n.soo

···················:.1····

_

I

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r

0.250

1----2.625 ----!'"t"--1.875

---:

Figure 2-20 Clevis sketch.

2.

Create the sketch shown above and extrude it symmetrically 0.5 inch. (Total

height will be 1.0 inch, 0.5 above the sketch plane, 0.5 inch below.) 3.

Create a new sketching plane on one of the yoke fingers and sketch the opening

shown. The two semicircles are separated by 0.25 inch. Tangent line and trim will be useful.

DO.SOO

c

r

0.500

1---0,500

-J

Figure 2-21 Slot sketch. 4.

Extrude this sketch through all, removing material.

We obtain the solid model shown next.

L.

2-15

Placed Features, Assembly

Figure 2-22 Complete clevis.

To this we want to add the stem and pin to complete the assembly. First hide the clevis. 5.

1 Parts, 1 Body> Solid> Right Click> Hide Body

6.

We'll create the stem first. View the XZ sketch plane and sketch the rectangle and circle below for creation of the brick-shaped stem extrusion. Use General for the linear dimension definitions.

t

06

,.

L7

L2

...................... ~- ...................................... \

•

..

I

vst----! ho------IIS---·

z

Figure 2-23 Stem sketch.

Refer to Figure 2-20 and give the L2 and V5 placements dimensions the values shown below.

Placed Features,

2-16

Assembly

8 Details of 5ketch3 Sketch

sketch3

show Constraints?

a Dimensions:

No

6

C06

0,5in

DL2

0,675 in

OL4

0,5in

OL7

0,5in

DV5

1.5 in

------; 4 in

Figure 2-24 Stem sketch dimensions.

7.

Switch to Modeling, Select the sketch of the Rectangle Extrude.

with Circle,

8.

Details of Extrude> Operation> and Depth> 1.0 (See below.)

Both _ Symmetric,

Add Frozen, Direction>

Click

The Add Frozen option adds the stem as a new, separate object and does not merge the new geometry into the existing clevis. The two parts remain separate.

J :)

9.

Generate

10.

2 Parts, 2 Bodies> Solid (Clevis) > Right Click> Show Body

Generale

Details ofEKtrudelO Extrude BaseObject

°

Extrude1 Sketch3

Operation

AddFrozen

DirectionVector

None(Normal)

Direction

Both· Symmetric

Type

Fixed

i

FDl, Depth(>0) 1 in

As ThlnfSurfece? MergeTopology?

No Ves----I

Figure 2-25 Stem extrusion and clevis.

Lastly we need to create the fastening pin that holds th bl plane to sketch on. e assem Ytogether. Create a new

2-17

Placed Features, Assembly 11.

Click XL Plane > Click the new plane icon Generate ] :)

*" on the third

line of icons >

Generate

~ A: Geometry - DesignModeler File Create

Concept

Tools

View

I

\ XVPlane Tree Outline

Figure 2-26 New plane icon. 12.

Right click on graphics screen> View> Bottom to get the view shown below.

z ......................

Figure 2-27 View for sketching pin. 13.

Sketch> Circle D2

Details View

EJ

Details of

-,

Sketch6

sketch

Sketch6

Show Constraints? No

EJ

Dimensions: 2

EJ

Edges: 1 Full Cirde

...............

Cr69

";...o---------'V3------!

Figure 2-28 Pin sketch.

Placed Features, Assembly 2-18 . is' Dimensionits diameter and location from the Z Put the center of the circle on t?e X Ax, h rizontal distance from the Z Axis to 1.5 Axis. Set the diameter to 0.5 Inches and the 0 inches. (See Figure 2-20.) Now create the pin extrusion using this sketch. 14.

Switch to Modeling, Select the sketch of the Circle, Click Extrude.

15.

Details of Extrude> Operation> Add F rozen,. D"tree tion > Both - Symmetric; Depth> 1.25 Details View

8 Details ofE>
Extrude 13

Base Object

Sl
Operation

Add Frozen

Direction Vector

None (Normal)

Direction

Both - Symmetric

Type

Fixed

l

--

......

~

.

FDI, Depth (>0) 1.25 in

As Thin/Surf ace?

No

Merge Topology?

Yes

Figure 2-29 Final clevis, stem,pin assembly.

At any time use the middle mouse button to rotate the view so you can see the sketch plane with respect to the rest of the model and tum the axis and dimensions on/off by clicking the icon on the second row. ~ 16.

Save your work. We'll use an assemblysuch as this later.

2-8 TUTORIAL 2F - ALTERNATE SOLID MODELER Finally we outline the procedures to utilize an alternate solid modeler such as Pro/E, CATlA, SolidWorks, etc. for use with ANSYS Workbench projects as an alternative to DesignModeler. 1.

Start the alternate solid modeler and create the clevis, stem, and pin parts discussed above.

2.

Create the Clevis-Stern-Pin Assembly in the Alternate solid modeler.

3.

Using the Alternate Solid Modeler, Save the Assembly in the STEP or IGES format

2-19

Placed Features, Assembly

STEP (Standard for the Exchange of Product Model Data) and IGES (Initial Graphics Exchange Specification) are industry agreed upon neutral file formats for the exchange of modeling information.

Solid Modeler

-..

STEP or IGES

~

DesignModeler

Figure 2-30 Neutral file transfer. 4.

Start ANSYS DesignModeler ,

File > ~ Import External Geometry> Generate

5.

!

File

[11

Create

Concept

Tools

View

.1

:) Generate

Help

Refresh Input

{(l Start

Over

k5 load

DesignModeler Database, , .

lid Save Project IifI Export .. , ~

Attach to Active CAD Geometry

li1J

Import Extern,:!l Geometry FIle, ..

,

Import Shaft Geometry. , ,

~

Write Script: Sketch(es) of Active Plane

o!\ Run Script liii Print [j} Auto-save

Now

Restore Auto-save File Recent Imports Close DesignModeler

Figure 2-31 Import External Geometry using STEP or IGES. Another way to utilize a solid modeler other than DesignModeler is to establish a direct link between the DesignModeler and your preferred Solid Modeler. With the alternate solid modeler running and the part/assembly you created in the alternate modeler as the active session in that modeler, you can start DesignModeler and simply Attach to Active CAD Geometry and Generate the model. See below.

Placed Features,

2-20

6.

File > ~ Attach to Active CAD Geometry > Generate

Assembly

1 -/~Generate

@;'J Refresh Input ..{] Start Over

fS load

DesignModeler Database".

Q Save Project ~

Export".

~ Attach to Active CAD Geomett;1 ~

Import External Geometry File., ,

,

Import Shaft Geometry".

c:i!.

Write Script: Sketch(es) of Active Plane

~

Run Script

tit Print ~

Auto-save Now Restore Auto-save File Recent Imports Close DesignModeler

Figure 2-32 Assembly attached from an active ProlE session. This direct link also gives you the ability to initiate a Workbench session directly from your Solid Modeler. The geometry will be transferred automatically and need only be Generated in DesignModeler to become available.

~

Named Selection Manager

t) Workbench

Help

About Workbench Geometry Interface ANSConConfig ANSVSGeom

Figure 2-33 Start Workbench from Pro/E menu it 1

em.

Placed Features, Assembly

2-21

~ A: Geometry

j ..

2

fIi

Geometry Geometry

• 1.,;;;";;=

Geometry

Create

Concept

t ~ ~ IB 101J

A ~

File

- DesignModeler

.../

4

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T0015 \/lew

~IJMi

J J

:)~erate

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mExtrude

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._{Surf". ~ Blend

XVPlane

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XVPlane ZXPlane

.-.iii'il ..... *"

YZPlane

Attachl 1 Part, 1 Body

t!I

Figure 2-34 The part from ProlE shows up automatically as geometry object in DM.

Use the ANSYS utility CAD configuration manager to help install the geometry interfaces to the alternate solid modelers you wish to use. fQo

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Figure 2-35 CAD configuration manager.

2-9

SUMMARY

The three tutorials in Chapter 2 illustrate basic placed feature creation and simple assembly modeling in ANSYS DesignModeler. In the next chapter we will extend these ideas to more complex parts and introduce additional solid modeling options.

2-22

2-10

Placed Features, Assembly

PROBLEMS

2-1

Use the ideas presented above to add holes, blends and chamfers to the parts you created as end-of-chapter problems for Chapter 1.

2-2

Create a linear pattern of holes in a straight line on a rectangular plate of your design.

2-3 Use the holes in the exercise above to create a multiple hole pattern in the other direction of the plate.

Figure P2-2

Figure P2-3

2-4

Create a solid model of the object shown using the dimensions in Chapter 5.

2-5

Place a hole as shown below in the part created in Chapter 1.

2-6

Create a solid model of the object shown using the dimensions in Chapter 8.

Figure P2-4

Figure P2-5

Figure P2-6

Placed Features, Assembly 2-7,8

2-23

Create solid models of the objects shown. y

L.

Dia=4mm

D = 0.75 inches (5 places) 2.0.0.5

ro=1.5 _

d = 1.5

-1+----1:-\--"

Figure P2-7

I = 0.5

Figure P2-8

2-9,10 Supply your own dimensions to create a solid models with similar proportions to those in the objects shown.

Figure P2-9

Figure P2-10

2-24

NOTES:

Placed Features, Assembly

Modeling Techniques

3-1

Chapter 3 Modeling Techniques

3-1

OVERVIEW

This Chapter discusses modeling techniques that illustrate the flexibility inherent in the feature-based parametric modeling of DesignModeler. We consider the use of • Parameters • Other CAD systems • Surface and line models

3-2

INTRODUCTION

The defining dimensions in the sketches, extrusions, revolves, sweeps, and placed features discussed in the previous Chapters were described using fixed numerical values according to the situation. In parametric design modeling we wish to assign parameters to these quantities so that they can be varied to fit various design requirements. It is also possible to write equations that relate the required variation in certain parameters in terms of other parameters. For example, it might be important for a hole always to be centered in a bracket even if different designs require that the bracket width change with application. Tutorial 3A illustrates this use of parameters. DesignModeler is a full-featured parametric design modeling system that provides for importation of models from other CAD systems and also allows the user to export models to other CAD systems. One vehicle for doing this is the use of the standard neutral file formats IGES (Initial Graphics Exchange Specification) and STEP (Standard for the Exchange of Product Model Data), agreed upon standards for the transfer of models between systems.

Modeling Techniques

3-2

Parts in DesignModeler are composed of Bodies whereas Assemblies may be composed of Parts. We illustrate these concepts also in this Chapter. 3-3

TUTORIAL

3A - PARAMETERS

The steps below illustrate the use of parameters and parametric equations to define relationships required for the execution of a particular design. The part in question is shown in the figure below. Here we wish the long leg of the bracket always to be 1.5 times the length of the short leg. The bracket thickness is to be constant. These invariant design requirements are accomplished using parametric relations in Designlvlodeler,

1.

Start ANSYS Workbench and use polyline to sketch on the XYPlane an Lsection 25 mm x 15 mm x 2 mm thick. Sketching> Dimensions> Display check Name and Value. ,

Sketching Toolboxes

r.raphl(s

-

-

r--

O,,'W

....J:-

Modty Dimensions

1-

i

-

<,

~General

!!=!! Horizontal

I[v""',,

25.(lJI)

~lengthJDistance

V1

('0,00, 8rMmel:er

&Anole

¥1 Semi-AutOlMt.Ic

I

~Edt

SiMove IE-t,

~",play

......

Name: ~ VMJe: P

ConstrMlts

s:

Settnos

SMt""'" Mode ....

Figure 3-1 Bracket

2.

Select the sketch and Extrude it 10 mm (Save a

Sketch!

Sketch Visibility

show Sketch

Show Constraints? No EI Dimensions: 3 H2 , VI

-

V3

f hi t IS model for use later.)

BaseObject

Sketch

l

0

El Details of Extrude! Extrude

EI Details of Sketch!

,

copy

Operation Direction Vector Direction

Type !5mm 25mm 2mm

Extrude I Sketch! Add Material None (Normal) Normal Fixed

;:j FDI, Depth (>0) 10mm As Thin/Surface? No Merge Topology?

Figure 3-2 Sketch and extrusion details.

Yes

Modeling Techniques

3-3

The figure above shows the details of the sketch and extrusion. The sketch and extrude details boxes give us manual control over the size of the part. Edit anyone of the dimensions shown in these detail boxes then click Generate, and you see the part size change immediately. However in this exercise we want to access the dimensions used for this part and tum some of them into parameters that will provide greater control over the part dimensions and the interrelation between them. 3.

First click on Sketch I in the tree outline to bring up the details window then Click the check box just to the left of the dimension VI in the Details of Sketch!. (Your numbers may be different.) q.

Details View EJ Details or 5ketch 1 Sketch Sketch Visibility

Create a new Design Parameter for dimension reference XYPlaneV1?

Sketch! I Show Sketch

Show Constraints? No Parameter Name:

B Dimensions: 3 OH2 D OV3

r~

15 mm 25mm

OK

2mm

..,

Cancel

Figure 3-3 Dialog box for parameter XYPlane.VI. XYPlane.VI is the dimension of the long leg of the bracket. Notice the 'D automatically placed in the check box to indicate that this quantity is 'Driven' by parameters and parameter relations. It is usually most useful if the parameters are given names meaningful to the part. The XYPlane.VI parameter will be named 'LongLeg'. (XYPlane.H2 will be named 'ShortLeg' and Extrudel.FDI will be named 'BracketWidth'.) Enter LongLeg in the Parameter Name box and Click OK.

@

A: Geometry - OesignModeler

Create 8 new Design Parameter for
Parameter

Name:

ILongleg

OK

Cancel

Figure 3-4 XYPlanel.VI parameter.

Modeling Techniques

3-4 Do the same for XYPlane.H2 and enter the name ShortLeg.

LEJ

ANSYSWorkbench

Create a new Design Parameter for dimension reference

XYPlane .H2?

IShortLegl

Parameter lIame:

OK

1

Cancel

Figure 3-5 Dialog box for parameter XYPlane.H2, ShortLeg. We will leave the check box for V4 alone since the thickness V4 is to remain constant at 2mm. 4.

Select Extrudel and Click the check box just to the left of the dimension FDl in the Details of Extrudel. Accept this Design Parameter; Click OK.

EI Details ofE>
Extrude1

Geometry

Sketch!

Operation

Add Material

Direction Vector

None (Normal)

Direction

Normal

ExtentType

o

Fixed ""C ="-'m'--m-------l lO

As Thin/Surface?

No

Merge Topology?

Ves

Create a new Design Parameter for dimension reference Extrude1.FD1 ?

Parameter Name:~

OK

Cancel

Figure 3-6 Dialog box for parameter Extrude 1.FD I. Extrude I.FD I is the parameter for the length of the extrusion. Enter BracketWidth the Parameter Name box and Click OK.

rgJ

A: Geometry - DesignModeler

Create a new Gelugn Parameter for dimension reference Extrude1. FD1?

Parameter Name:

IBracketWidth

OK

Cancel

J

Figure 3-7 Extrude I.FD 1 parameter.

in

Modeling Techniques

3-5

We now have defined all of the parameters we want for the bracket dimensions. To view these, click the Parameters icon SParameters or use the tools menu. 5.

Tools> Parameters

The parameters we have defined and their values are now shown at the bottom of the screen under the Design Parameters Tab.

25.000 \11

i ..........

.....

2000

I

Madel View Print Preview

I

Parameter Manager Sha
/ Design Parameters

Figure 3-8 Initial dimensions.

6.

Click the Parameter/Dimension

Assignments tab.

Modeling Techniques

Parameter Manager Parameter

Nanaqer

.- .-----.:;-

--~---.-::-;:-=~::. ";;.--~~

'Bracket Relations

Extrrude L, FDl

:: @B:rackettJidth

XYPlane. Vl XYPlane.H2

@LonqLeq

Extrude!.

@5ho"tLeq

XYPlane.Vl

=

l.S*85hortLeq

XYPlane.H2

=

@ShortLeq

=

FDl :: BBt:8.cketlJidth

,/ Design Parameters

Parameter/Dimension

Assignments

Design Parameters

Parameter/Dimension

Assignments

1

Figure 3-9 ParameterlDimension Assignments and Relation Equations. The ParameterlDimension Assignments window displays equation assignments used to drive the model dimensions. The design parameters are given an "@" prefix. We can edit information in this window and add to these definitions in order to impose the relations between dimensions that we desire. Comments are preceded by the "#" character. In the example under consideration we want the XYPlane.Vl dimension to be 1.5 times the ShortLeg dimension and the other values as defined. Enter these relations in the Pararneter/Dimension Assignments window as shown below. Then press Generate to create the bracket with new size variables as shown in the figure below.

Oet~ils View 8 D~tailsof b:trude 1

22500

Extrude

Extrude1

BoseObject

Sketch1

Operation

AddMaterial

Direction Vector

None (NormaO

Direction

Normal

Extent Type

Fixed

o

FD1, Depth (>0)

10 mm

As ThinfSurFace?

No

Mer~eTopoIOl;lY?

Ves

V1

JModel View

I Print Preview

2.000

,---'---------

Parameter Manager 'Bracket

Relations

Extrudel. FDl = ~BracketlUidth . XYPlme. VI = 1. 5~~ShortLeg XYPlme.H2 = eShortLeg

Figure 3·10 Newly sized bracket.

Modeling Techniques

3-7

Notice that the H2 dimension remains at 15 rnm and the height (long leg) is adjusted to 22.5 mm. These relations persist and are enforced for any subsequent changes we make to ShortLeg. For example, Click on the Design Parameters Tab to edit the values shown. If we change the ShortLeg to 5 mm and click Generate, we get the part shown next. Parameter Manager

ShortLeg = 5.00000000 LongLeg = 25.00000000 BracketWidth = 10.00000000

Design Parameters

Parameter/Dimension Assignments

Check

Figure 3-11 Edit dimension values.

The H2Nl proportions will change according to the relations assigned, but the bracket thickness will remain 2 rnm.

/L

f ..5001]

!

// I

H2 •..;

Figure 3-12 Newly sized bracket.

7.

Click the ParameterlDimension

Assignments Tab

Modeling Techniques

3-8

h I ti s au have entered. For example The Check Tab is used to check the syntax oft. ere a tequation a syntax error will be if @LongLeg appears on the left of an assignrnen , created, and the part will not be generated correctly.

· . Assignm.ents Parameter / Damens aon . I 'Bracket ReLet.a cms I

If HI DesignHodeler 1 I Com.m.ent 2

I

Com.m.ent

I

I

3 I Feature Dim I 10.0000 I ExtrudeLFDl 4 I Plane Dim I 1.5000 I XYPlane.Vl 5 I Plane Dim I 5.0000 I XYPlane.HZ

,,#

DesignHodeler 1 I

2

I

3 I

Design Parameters

---

Output

=

= =

@BracketWidth 1.S*@ShortLeq ~ShortLeq

Design Parameter Assignments Output 5. 0000

I @ShortLeg

I 25. 0000

I

I @LongLeg

J

10. 0000

I @BracketWidth

Parameter/Dimension Assignments ~

Figure 3-13 Check Tab. 8.

Change back to the original dimensions when you are finished Parameter Manager to Close the window. Save T3A.

and Click

Design parameters appear as the CAD parameters in Analysis Modules if their names contain the Parameter Key defined when starting the anaylsis. The default parameter key is DS. If all design parameters are to be sent to the associated analysis, make the parameter key blank when you start the simulation. 3-4

OTHER CAD SYSTEMS

DesignModeler provides support for a number of other widely used CAD systems. When using Windows-based systems, you can bring a model currently being edited in a CAD session on your computer (ProlE, CAIlA, etc.) into DesignModeler by using File> Attach to Active CAD Geometry The model then appears as an object in the feature tree of your DesignModeler session. Alternate CAD system geometry interface support includes Autodesk Inventor,. Autodesk .Mechanical Desktop, CATIA, Pro/ENGINEER, Sohd Edge, SohdWorks, and Unigraphics. The IGES and STEP neutral file exchange formats for 2D 3D CAD product models, drawings, or graphics is also supp rted b DesignModeler. (See also Chapter 2) The bracket model hoe h y . ProIENGINEER, saved in the IGES f s own was created in t here orma,ten importe d'D'nMdl' In esig 0 e er using

S . rt Figure 3-14 IGE rmpo .

Modeling Techniques

3-9

File> Import External Geometry File> bracket.igs > Generate Models created in DesignModeler can also be exported in the IGES or STEP format for use with other CAD, graphics, or analysis software. Use the following sequence to export the file in the current DesignModeler session. File> Export>

3-5

IGES (*.igs, *.iges)

(or STEP)

SURFACE AND LINE MODELS

Surface models are necessary if one wishes to perform analysis using simplified planar or 3D surface models instead of solids. Line models are needed when line elements are being used in engineering truss or beam simulations. The important shell (plate) engineering bending models are supported in Workbench DesignModeler by providing for the DesignModeler creation of surface models subsequently analyzed using ANSYS plate element technology. Beam bending is supported by the creation of line models to which beam cross sections are attached. Planar surface models are used to support analysis of Plane Stress, Plane Strain and Axisymmetric problems.

3-6

TUTORIAL 3B - PLANAR SURF ACE MODELS

We will use the L section solid of Tutorial 3A to create a planar surface model in this tutorial. Later we will use this same solid to create a three-dimensional surface model. 1.

Start DesignModeler and Open the file for Tutorial 3A. The part is 15 x 25 x 2 x 10 mm long.

25.000

V1

L.~:::::1'Df-" 2.000

...

~5.000 :

•

HZ

Figure 3-15 L-shaped section.

2.

Select the sketch in the tree outline

y

Modeling Techniques

3-10 3.

Concept> Surfaces from Sketches ~ncePt A: Geometry

""

. ,,;faXYPlane

',,8 BIllD

Modeling

Lines From Points

Cllines From Sketches

fiJ Lines

1 ...,,;fa ZXPlane :. ,,;fa YZPlane ffi·,,~ Extrude! i±1.. ,,~ ! Part, ! Body

Sketching!

Tools View Help

3D Curve

"

Split Edges

()

Surfaces From Edges

~

Surf aces From Sketches

~

I

From Edges

\1\

Surfaces From Faces

,

Cross Section

Figure 3-16 Surfacesfrom sketches. 4.

Details of SurfaceSkl; Base Objects> Apply, Thickness> 1

Tutorial3A ." ;faXYPlane

....."*'"C!

Sketch! ZXPlane YZPlane

Cancel

,,*, I±i "I!l, Extrude!

Operation

Orient With Plane Normal? Yes Thickness (>=0)

",61

! mm

i±1 . ,,(il

-

! Part, ! Bd

X

Delete

I~Figure 3-17 Generatethe surface. 5.

Right Click SurfaceSkl > Generate

This creates the surface model. The solid we startedwith is no longer needed and may be deleted. 6.

Select Extrudel > Delete> OK

The surface model is shown in the figure to the right. Notice that no thickness is shown. However the I mm thickness we supplied will be carried as a numerical value into the selected analysismodule. 7.

'I

Save this model as T3C Figure 3-18 Surface model from Sk I.

Three-dimensional surface models can be developed from solids using the methods described next.

Modeling Techniques

3-7

3-11

TUTORIAL 3C - 3D SURFACE MODELS

Again use the L section solid of Tutorial 3A.

1.

Start DesignModeler and Open the file for Tutorial3A

once again.

We want to capture the middle surface of the bracket. 2.

Tools> Mid-Surface

([J Freeze ~

Uofreeze

~

Named Selection

~

Attribute

~

Jvlid-Surfece

...

Joint

@

Enclosure

...

Symmetry

iii Fill

ue

Surface Extension

Clll

Surface Patch

...

Surf ace Flip

Figure 3-19 Mid-Surface tool. 3.

Details of MidSurf2 > Face Pairs

4.

Use Ctrl Select to sequentially pick all the front and back face pairs on the bracket model> Apply.

Intersect Untrimm, ., No

Figure 3-20 Mid-Surface face pairs. 5.

Generate:)

Generate

To create the surface.

Modeling Techniques

3-12 Notice that this is a three-dimensional surface model.

•

Graphics

A: Geometry

,I @

B

*y'CI **-

XYPlane Sketch!

,I

',1

ZXPlane

,I

YZPlane Extrude 1

I±J B

,I

Ii!!,

,,0 MidSurf! ! Part, ! Body

,I

,I

Sketching

tll!lll!lill

Modeling

I

Details View

B Details or Body Body

Surface Body

Thickness (>=0)

2 mm

Thickness Mode

Refresh on Update

Surface Area

355 mm'

Vertices

6

fluid/solid

Solid

Figure 3-21 3D surface model of the L shaped section.

The thickness of the Surface Body is independent of the solid whose mid surface was used and is set by the user in Details of Body box as shown above. This thickness value (2 mm in our example) is carried into the analysis systems modules and is used for the calculations there. More detail on this is given in Chapter 8.

3-8 TUTORIAL 3D - LINE BODY MODELS In the final tutorial of this chapter we develop a line body model to which a cross section is assigned. This model is then used in the analysis module to compute response using beam element modeling.

structural

Modeling Techniques

3-13

1.

Start Workbench and DesignModeler. Set the units to inches.

2.

In DesignModeler sketch on the XY Plane.and use lines to Sketch a portal 120 inches high and 72 inches wide (two verticals and one horizontal line across the top). See the next figure.

120,000 VI

Figure 3-22 Portal. ...... -~-~-4·

3.

Modeling> Select the Sketch

4.

Concept> Lines from Sketches> Base Objects> Apply (The sketch is the base object.)

*''"eJEmllI *'

'" @ A: Geometry

l;J ""

XYPlane

: ',,*,

ZXPlane

L "

YZPlane 0 Parts) 0 Bodies

1...

0(

r Concept

Tools

View

,

lines From Points

~

lines From Sketches

ItJ

lines From Edges

\1\

3D Curve

Details View

Heip

Car

..... Split Edges

~

Surfaces From Sketches

~

Surfaces From Faces

•

Figure 3-23 Lines from sketches. A: Geometry

Generate This generates the line body without a cross section. Next we assign a cross section to this line.

",:f.

XYPlane Sketch! "",:f. ZXPlane ",:f. YZPlane 00 Linel

",c.2I

..,.c9

6.

Figure 3-24 Generate Line Body. Concept> Cross Section> Channel

..

H2

Cross Section

/

_ 72.000

__ Surf aces: From Edges:

5.

···

13 "'~

Sketching

1 Part, I Body

-I,D.

Modeling

I

Details View

We take the default size which is the 3 x 6 x 1 EI Details inch section shown below and assign it to the Body Line Body as shown in the second figure below: Faces Line Body> Details> Cross Sctn. Edges

Vertices

or line Body Line Body 0

3 4

Cross Section Not selected

w---------------r-

z

Modeling Techniques

3-14

I

6.000 concept

"

Tools

View

Help

W3

lines From Points

6J lines

From Sketches

ijJ

Lines From Edges

V\

3D Curve

IliI

Rectangular

•

Circular

3.000

o Circular Tube

W2

~ Channel Secbon

.... Split Edges

Co

Surfaces From Edges

C2I €J

:ii: 'i.

1.000

I Section Z Section

t3

Surfaces From Sketches

.. l Section

Surfaces From Faces

JL

T Section

A

Hat Section

3':~""···"·'··..L"'-T'r~

Cross Section

..

I:iI Rectangular

Tube

III User Integrated ~

1.000

User Defined

tl

Figure 3-25 Choose Channel Section.

Tfee Outline B.,.

*' .. c:'iI .,...**"'

A: Geometry

8

S

..

XVPlane

,,63

ZXPlane YZPlane line!

E1

"til

EJ

v

r

Sketch!

.. c:'iI Sketch 1 1 Cross Section

.,.e Channell 1 Part) 1 Body

'" ..... line Body

120000 Sketching

Modeling

I

V1

Details View

EJ

Details: or Line Body

Body

line Body

Faces

o

Edges

3

Vertices

1 Not selected None

.:

72000 1---

H2

----"'i

Figure 3-26 Assign the channel to the line body.

7.

View> Show Cross Section Solids (Displays the orientation of the section.)

Modeling Techniques

f

[View

3-15

Help Shaded Exterior and Edge,

IF::::

, 1

Frozen Body Transparency

, ,

Edge Joint,

r

r.:.:- Cross Section Alignments Display Edge Direction

T::r:;-

I

Display Vertices

120000

Cross Section Solids

V1,

Ruler Triad Outline

Windows

•

•

/"--------. J2.D00 H2

....

r

-

~

....

Figure 3-27 Show cross section. The arrow normal to the portal plane (green on your screen) is aligned with the long edge of the channel cross section. Display the section orientation: Uncheck Cross Section Alignments, To adjust the orientation of the top beam select as follows. 8.

Turn on the Edge Selection Filter Reverse Orientation? > Yes

J~and

Pick the Top Line-Body Edge.

Figure 3-28 Close-up of section orientation.

3-16

Modeling Techniques

Detail, View

B line-Body Edges: 3 AlignmentMode

Selection

Cross Section Alignment Plane Normal AlignmentX

0

AlignmentY

0

AlignmentZ

1

Rotate

f-0-'-

__

-::1

..

Figure 3-29 Alignment options.

Figure 3-30 Reverse orientation of top cross section.

The adjustment options shown in Figure 3-29 can be used in a number of ways to obtain proper beam cross section orientation for the problem at hand. Some experimentation may be helpful.

9.

Save your work.

This Line-Body model can be expanded using the sketching methods described earlier to add more elements and dimensionality to the model. We add vertical and horizontal lines sketched in the YZ Plane and a Concept> 3D Curve diagonal line joining the two outer vertices. This modification is shown in the following figure.

Modeling Techniques

3-17

....

,

,

~

t

.--i

<;

....... ......

v

,:J...

x

Figure 3-31 Expanded Iine-body model.

In Chapter 8 we will attach this model in the ANSYS analysis system to analyze the structure using beam elements. Line bodies can also be created by connecting points that are entered from a text file. First create a text file with your list of points as shown below. The first entry is the Group number followed by Point number, then X, Y and Z coordinates.

1

1

0.0

1

2

2.5

1

3 -1. 5

0.0 -2.0

0.0 1.5

3.2

2.1

etc. Figure 3-32 Text file of points. Use the Point icon from the toolbar •

~Point

to open the

Sketching

Modeling

I

-)' Generate

DetaIls box below and Generate to Read Details V,ew -- them into DM. Finally Concept> Lines from Points, EJ Detail. or (Click point to point) Apply and Generate to create Point your line-body model. Type Derinition

Figure 3-33 Locate and read points.

q.

Point! Point! Construction

Point

From Coordinates File

Coordinates File C:\Doc." \nodeJloints.txt Tolerance

Normal

3-18 3-9

Modeling Techniques SUMMARY

Chapter 3 tutorials introduce the use of DesignModeler parameters and briefly discuss how to make use of other CAD systems, how to create assembly models and models that are not solid models but surfaces or lines for use in down-stream engineering analysis.

3-10 PROBLEMS 3-1

Create parameter relations for the model of a cylinder (shown below) so that the height of the model is 6 times the wall thickness and the exterior radius is 3 times the wall thickness. The wall thickness and interior fillet are constant. See also Figure 5-1. Are there size changes that produce invalid solid models?

3-2

Parameterize any of the DesignModeler parts created earlier in your study and examine the effect on the dependent parameters of changing a base dimension value. Are there size changes that produce invalid solid models?

3-3

Create placed remain invalid

parameter relations for the model in Figure P3-3 so that the large hole is at half the height of the part and always centered. The other dimensions unchanged. Also see Figure 5-17. Again, are there size changes that produce solid models?

fillet radii 10 & 20

lS. no

i 25.00 ,

200,00

10 dia 15 from edges

.-_L X

Figure P3-1 3-4

Figure P3-3

Import an IGES or STEP file from another CAD system If one t il bl . one export an d save an IGES or STEP file from Desl·gnM d I IS not avai a e, D .gnM d I· .. 0 e er, start a new eSI 0 e er session and try Importmg that IGES or STEP fil ne,

3-5

If another CAD system is available and the link to ANSYS W kb . . oM a d e Ier to attach the geometry for a part th t i .or ench. established use D eSlg . ' that CAD system. a IS m an active session of

3-6

Create a model of the object shown. Diameter A = 5 D. 1.5 mm, Cone dia 8 x dia 3 x B =10 mm, All Roun=~'o 51ameter C = 15 mm t = mrn, Use a pattern to create the three equally sp d h I· mm, All Holes 1.5 ace 0 es on the base as shown.

Modeling Techniques

3-19

Also define parameters and enforce a relational equation to insure that the height B is always twice diameter A. Make a change in A to show the effect on B.

A

c

Figure P3-6 3-7

Figure P3-7

Create a line-body model of the framed beam structure shown. The beam cross sections are circular tubes 5/16 inch in OD with a wall thickness of 0.095 inch. Dimensions in the figure are in inches.

3-8 A circular ring can swing on a cylindrical pin as shown. Choose your own units and dimensions and create a model of the assembly indicated above. (Image from ANSYS VMDM003)

y

~x Figure P3-8 3-9

P3-11

Develop a 2D surface model for the ring of problem 3-8.

3-10 Develop a 3D surface model for the Bracket of problem 3-3. 3-11 Develop an assembly model for the parts shown in Figure P3-11 from VMDM003.

3-20 NOTES:

Modeling Techniques

ANSYS Mechanical I

4-1

Chapter 4 ANSYS Mechanical I

4-1

OVERVIEW

ANSYS Workbench provides tools for the user to analyze the behavior of Electric, Fluid, Magnetic, Mechanical, Thermal systems and problems where more than one physical behavior is considered. In this Chapter we consider: • Stress response of a plate with a central hole. • Stress response of a plate with various FEM mesh densities. • The use of convergence criteria for controlling solution accuracy.

4-2

INTRODUCTION

Evaluating the response of a mechanical part or system in Workbench involves accessing the Geometry, assigning the Materials, applying the Loadings and Displacement Boundary Conditions, Solving the system Equations, Reviewing/Reporting the Results, and Updating the model if desired. An outline of this process is shown below. 1.

Create and Attach problem Geometry.

2.

Assign Materials.

3.

Establish Contact Conditions if applicable.

4.

Preview the FEM Mesh and set up Mesh Controls if desired.

5.

Apply Loadings and Displacement Boundary Conditions.

6.

Select Results to be computed and displayed.

4-2

ANSYS Mechanical

7.

Solve the system governing equations.

8.

Review the Results.

9.

Set problem Parameters if desired.

10.

Create Reports ofthe response as appropriate.

11.

Update the CAD model if necessary.

To develop confidence in the process we start in Tutorial 4A by solving a simple structural static mechanical response problem. In this problem we can check the maximum stress result separately by a hand calculation.

4-3

TUTORIAL 4A - PLATE WITH CENTRAL CIRCLUAR

HOLE

In this tutorial we will use ANSYS Static Structural Analysis to compute the maximum deflection and stress in a thin steel plate with a central hole. Its dimensions are 1000 mm long, 400 mm high and 10 mm thick. The central circular hole is 200 mm in diameter as shown in the figure below. The plate is loaded in the long direction by a tensile force of100 kN. I

1""-'500 000 ---, I

0200000

/

Figure 4-1 Thin plate with central hole' dim . . , enSIOns III rom. First we need a solid model of the late . another solid mOdeling system. ~nce' t~~dthis can be.created with DesignModeler or plate are on planes of plate geomet central honzontal and vertical axes of the analyze only a quadrant of the part tory~rnmhetry as w~lI as loading symmetry, we need o am t e stress dIstribution. Use your solid modeler to trim the model t o a quadrant as shown next.

I

4-3

ANSYS Mechanical I

Y

Figure 4-2 Quadrant of plate. We follow the steps outlined above skipping those not needed in this tutorial. In working through this and all the other tutorials keep in mind that your results may vary slightly due to sight difference in generated meshes. 1.

START UP: > Start ANSYS Workbench, begin a new Project.

tJ

~ eJ

ANSYSClient Licensing EKM

•

Help Meshing Utilities

~ 1\ 1\

~

Mechanical APDL (ANSYS) 14.0 Mechanical APDLProduct Launcher 14.0

U Uninstall14.0 • ~

Worl
Figure 4-3 Starting ANSYS Workbench in Windows. Double click Geometry under Toolbox > Component Systems to initiate the geometry object in the Project Schematic. See the next figure.

j··--------------------------AN-s~Y~S~M~e-c~h~an~i~ca~I~I----'!"" 4-4

. Rle

lIiew

orkbench

Tools

JNew u '00

Units

Help

in Save ~ ~ Save As... en... lB

•

~ Refresh Project:

iiVImport".

~e

Project

q X "

8 Analysis Systems

e

Design Assessment A

Electric

II Explk:it Dynamics IiJ Harmonic Response U Linear Buckling

e o

Magnetostati(

OJ

Random Vibration

2

Mod_

O Modal (Samcef) II Response

Spectrum

Rigid Dynamics Static Structural

til

Static structural

(Samcef)

IJ Steady-State Thermal It Thermal-Electric Transient Structural

IITransient @ Component

Thermal Systems

~

AUTOOVN

~

BladeGen

•

Engineering Data

em

External Data

Q;J

Finite Element Modeler

1(IIIl A

External Connection

--

Geometry Mechanical APDl Mechanic,,) Medel

IGeometryl

Mesh

l!!

Microsoft Office Excel

II System

Coupling

Vista AFD Vista CCO ViSta RTD

I!l Custom systems_~

""-1

1!I Design Exploration

Figure 4-4 Project Schematic details. The question mark indicates that cell A-2 is incomplete. 2.

Select the small blue triangle for additional information. Click anywhere schematic to close the information box.

in the

Select a folder in a convenient location on your storage device and use Save As •.. to name the project T4A, Tbe project title, T4A, is displayed on the header as shown below and the Workbench project file T4A.wbpj and folder T4A files are created in the selected workspace. Take a minute to find and verify this, There are a number of ways to create and access geometry for your project. We discuss several, A., B., c., D., and E. in what follows,

4-5

ANSYS Mechanical I

A. » Create New Geometry in Design Modeler: Double click cell A2 to start Design Modeler. Select problem length units and proceed to create geometry as discussed in

Chapters 1 - 3. Save your DM work when you are finished. -

.

ANSYS Workbench

~

Select desired length untt:

r-

Meter

r

Fool

r:

Cenlimeter

r

Inch

r

Mlllimeler

r

Micrometer

r Always

use project unjt

r Always use selected untt r E.nable large model support OK Figure 4-5 A » Start new geometry in DesignModeler and set units.

B. » Access Previously Created Geometry in Design Modeler: Double click cell A2

to start Design Modeler. File> Load DesignModeler Database (See the next figure.) ]' A: Geometry - DesignModeler

r

File Create

@j

Concept

Tools

View

Help

Refresh Input

';!j Start

Over

0

DeSignModele, Database".

1 Load

(;I Save Project

IIExport. " Iji Attach Iji Import

to Active CAD Geometry External Geometry File ...

Figure 4-6 B » Loading existing DM file.

-------------------4-6

ANSYS Mechanical

C. » Access Geometry Previously Created and stored using another

solid modeler: SoIidWorks, etc) Double click cell A2 to start Design

(CATIA, ProIENGINEER, Modeler.

File> Import External Geometry File (Options include IGES and STEP formats) (See the next figure.)

i A: Geometry.

DesignModeler

File Creete Concept Tools View Help

/1;)

RefreshInput

':d Start Over E3 load DesignModelerDatabese... Q SaveProject ~

Export...

~

Attach to Active CADGeometry

.i1

lmport Extetndl Geornettv Fife .. ,

Figure 4-7

Be »

Importing from an alternate format.

This process starts the alternate solid modeler, loads that modeler's geometry to DeslgnModeler, and closes the alternate solid modeler.

file, transfers

the

D. » Access Geometry in Active CAD t . Modeler. sys em. Double click ceU A2 to start Design File> Attach to Active CAD Geometry

Tools View Help

~'

i1Impor~nal Figure 4-8 D»

-----

G~metry File...

Attach to A . ctlve CAD Geometry.

I

4-7

ANSYS Mechanical I

E. » Start Workbench from your alternate Solid Modeler. An example of this using ProlENGINEER is shown below. Note the ProlE icon is shown in cell A2 in the Workbench Project Schematic.

, Double click cell A2 to start DesignModeler, then use Generate :) ProlE geometry.

tj) Named

Selection Manager

Generate

to attach the

PIoiect Schematic

@Workbench Help

o About Workbench Geometry Interface A

ANSConConfig ANSYSGeom

2 Geometry

Figure 4-9 E»

3.

Starting Workbench from ProIENGlNEER.

Getting back to Tutorial4A, with the geometry attached, Double Click Toolbox> Analysis Systems > Static Structural to add the analysis to the Project Schematic. (Or drag it from the Analysis Systems column to the Schematic.) •

o @

Figure 4-10 Adding Static Structural Analysis from the Toolbox.

o m!l

x

q.

Fluid Flow (CFX) Fluid Flow (FLUENT) A

Harmonic Response linear BucldinQ

2

Magnetoslatic Modal

II Random

IIResponse

~ry lIibratlon Spectrum

Rigid Dynamics

S Sh~e

Optimizatton

III Static Structural

o

Steady-State

Thermal

m Thermal~Electric

I Statk Structural

Transient Structural

4.

To share the geometry, Left click on DM Geometry in cell A2 and drag it to Static Structural cell B3.

4-8

ANSYS Mechanical

A

2

I

B

,,--=

L: __

2 •

Geometry

3

(ill)

Engineering Data Geometry

4

Model

5

Setup

6

Solution Results Static Structural

Figure 4-11 Sharing geometry. 5.

Double Click on Model in cell B4.

The Workbench display now shows the Static Structural Analysis that is associated with this Project, and the tree Structure on the left contains project items that include Model, Geometry, and Mesh. See the figure below.

'"

Ed< "'"

~.

Q

HoI>

llit> Took

"I' I 'I' roo·

@ @

"'1",,,,_ $...

""Show"'""

Mesh:)~

~Mesh

Oulh

..

tJ

;;_.

roo roo e-

ibt ~

~ ,;:

HEdgoC_ • MeshCortrli ... .,-

@\

e.

@. ~

Q.

:;:,

e

A· A· A· A· A· " H I-Ir""",_

lb,

_ y

. ProJee:t

'" iii M....

l..)


4-. CCllll"dMte

[f} ....

B

.AI> static """ ....e

Systems

Structural (85)

....C3 Analysis Settings

}il11 FrictJonless Support

fl..Force Fi ~

SotuUon (86)

Figure 4-12 Plate quadrant in Static Structural Mechanical module. Since the geometry was. created using mm, the length units for the simulation should be mm also. Check the units usmg the Units pull-down menu Unit M . N s, mY, rnA) . m s> etnc (mm, kg, ,

6.

Highlight Material in the Details of "T4A" wind

ow.

-----------------1'4 4-9

ANSYS Mechanical I

7Units

Tools

I

Help

Metric (m, kg) NJ

S,

I :)~olve

(J

•

t$lI

Outline

'iIb

Project

8

VJ A)

f!1!I

Model (B')

8

.t~

Metric (em, gJ dyne, 5, VI A)

Frl'letnc (rom, kg, N 5, mV rnA) Metric (mm, t, N,

5J

Eb

j

J

B

j

u.s, Customary (in} Ibm, lbf

F

OF) 5,

Static Structural (OS) Analysis Settings B .,~ Solution (86) ~ Solution Information

,,(:4

V, A)

OF) 5) V,

Details of "HA"

A)

r±l Graphics 8 Definition

Degrees

~

Properties

Suppressed

Radians

Frad/s RPM

r;-

'18 .

Metric (urn, kg! IJN, SI V rnA) (ft) Ibm, Ibf,

-I'*'

.---

HA Coordinate Systems

~Mesh

mV, rnA)

Metric (rom, det, N, s, mV, rnA)

u.s, Customary

Geometry

)fil

No

Stiffness Behavior

Aexible

CoordinateSystem

Default CoordinateSystem

Reference Temperature

By Environment

8 Material Structur

Celsius (For Metric Systems)

at steel

Yes Ves

Kelvin (For Metric Systems)

Figure 4-13 Check Units and Material assignment. To return to the Project Schematic, Select T4A - Workbench running shown in the taskbar at the bottom of the screen.

from the programs

Figure 4-14 Workbench elements shown in the Taskbar. 7.

Double click Engineering Data, cell B2 to view the Material Properties Data for Structural Steel, the default material that has been assigned to this part.

B

A

Geometry

• 5 6

Solution

f •

7

9 Result,

I •

static structUfa! (ANSYS)

Figure 4-15 Project Schematic. Be sure View> Properties and Outline are checked. Properties for the default material Structural

Steel are shown.

·~--------------~ ANSYS Mechanical I

4-10 j Up d ate

. t Projec

A \07 Return to Project

:.fT1 I· I

V. Conp.."'Kt dOG 'U'

'::,. "

I~Ju~line of Schematic 82: Englneenng Data B

A

IEngineering Data Sources

q. X

y

"

D

C

Description

2 Fatigue Data at zero mean stress comes from 1998 ASME BPVCode, SectionB, Div 2, Table 5·110,1

3 Click here to add a new material

•

v

'" tlme Row -c_',. '-tru·tur:s15teel Pt operties or- vu .:1.

y

I.

1

'iB

2 3

I±I

6

EI

~

A

B

Property

Value

Density

I

C

ID

7850

kg m -3

.:.1 EJ

Isotropic Secant Coefficient of Thermal Expansion

r

Y!:l

Isotropic

X E

.~!N

Unit A

q.

ICJ

EI

Elasticity

f[]

.:.1

7

Derive from

B

Young's Modulus

2E+11

9

Poisson's Ratio

0,3

10

Bulk Modulus

1.6667E+11

Pa

11

Shear Modulus

EJ

7,6923E+10

Pa

0

12

I±I

16

I±I

24 25 26 27

'iB Alternating Stress Mean Stress E Strain-Life Parameters 'iB Tensile Yield Strength 'iB Compressive Yield Strength 'iB Tensile Ultimate Strength 'iB Compressive Ultimate Strength

Young's .. ,

IillI

Pa

n

.:.1

EI Tabular

[[J

EI 2,5E+08

Pa

2,5E+08

Pa

4,6E+OB

Pa

0

Pa

.:.1 EI ro .:.1 lE:l ro .:.1 [J ID .:.1 D []

Figure 4-16 Material properties for structural steel. Note that structural steel has Tensile and Compressive Yield Strengths of 250 MPa. and that because it's unknown, zero has been assigned to the Compressive Ultimate Strength. 8.

Select Return to Project (Topof sereen)

~RelurntO"'oject

The Mesh item in the project tree has a lighting bolt symbol next to it indicating that the finite element mesh for this simulation has not yet been created. Workbench simulation will automatically develop a finite element mesh appropriate to the problem. 9.

MESH: Right click Mesh and select Generate Mesh

4-11

ANSYS Mechanical I

The default mesh that is created consists of a little over one hundred three-dimensional 8 or 20 node brick elements as shown.

8-""

.

~--

,-._-

Project Model (84)

fil

*. - A'flmr"

$"".,)iSt

Geometry

[£- .....

Coordinate

8·

Systems ~---j

.,.s ~~:-_I"_,e_rt -\ ,;

_

Update

Preview Show :) Create ________

Pinch Controls


Gener ated nete

alb

11

Rename Start Recording

Figure 4-17 Meshing the geometry. 10.

Select Static Structural (B5) from the Outline tree structure (next figure). The Environment displays loadings and boundary condition options available for this analysis.

Since only the upper half of the plate is being analyzed, apply a Force of 50 kN to the right end surface. 11.

APPLY LOADINGS: Click Environment>

Loads> Force.

Environment ~ ....Inertial ... @"toads ... @" Supports ... ll-

Outline

la Project 8 ~ Model (04) [fJ

l±}-

.;fjI 0/*

I

@... Pressure

Geometry Coordinate

Systems

~Mesh

8

£:1 Static Structural (05) -

,,{;j,

EJ

@"Loads • @. Supports.

./

@" Hydrostatic Pressure

¥'

!d

Force

Analysis Settings

@.. Remote Force

?fi1 Solution (06) '. 'AIl Solution Information

'tI,

Bearing Load

Figure 4-18 Structural loads menu. ~

Be sure that the Face selection filter is highlighted @ and click on the area on the right end of the solid model.

·-------------------~ ANSYS Mechanical

I

4-12

12.

Geometry>

Apply (Note: It's easy to forget this step.)

13.

Define (the force) by (X Y Z) Components, X Component ~

.

_._,-,

'-~=:iellt-'~~ ~@.. ~~7lSi~s:-:-~·ii~.c~Olid~·it~~-;~:.::$Il,:.~"''''~FE~ ..:..-~~;.:·-=--= j

""""

Project

ril"'_

8"" Ij] I"1ofkI(B4)

;t... Coorchte

~'1 ......

B: static St:rudlWal

__

E

(ANSYS)

Systems ..

Stalk structural (85)

.2:i ArWtsis PQf~s~ .ft. """'

S- ~

.--.:

F.~ Tine: 1. s

.... 0 Mesh

B

= 50 kN

Force: 50000 N

Components: 50000, 0., 0, N

5ettnos

Solution (86)

-.AD SOlution

Information

."

Figure 4-19 Tensile loading. Next apply the displacement constraints; rotate the plate so that you can see the bottom, and small end. These are surfaces on planes of symmetry and no point on these surfaces can move across the plane of symmetry. Symmetry requires that we constrain the displacements perpendicular to these surfaces. We can use the Frictionless Support condition to do that. We also restrain the back surface also so as to prevent rigid body motion in a direction perpendicular to the plane of the plate. See the figure below.

~

Fixed Support

~

Displacement

til

K

Remote Displacement

(jK velootv

~

Impeder»

~

Ft ictionless Support

~

Compression Only Support

~

Cylindrical Support

e Boundar- '

I

Figure 4-20 Displacement constraints. 14.

Environment>

Supports> Frictionless Support

15.

Ctrl > Left Click to select the three surfaces> Apply.

4-13

ANSYS Mechanical I

B Scope Scoping Method

Geometry Selection

Geometry

3 Faces

B Definition Type

Frictionless Support

Suppressed

No

Figure 4-21 Frictionless Support constraints. Check your work by clicking on each of the items under Environment in the model tree to be sure the loadings and constraints are applied as desired. Or click Static Structural to see all of the constraints you have applied. If you find something wrong, just highlight the item in the model tree and edit it in the 'Details' box to correct the error, or Right Click, delete the item from the outline tree and apply the condition again. (Note that the back face is not really a plane of symmetry. To be absolutely correct we should have sliced down through the 10 mm thickness and analyzed an octant instead of a quadrant. However since the 10 mm dimension is so small in comparison with the other dimensions, there is little error in the approach we used. Try it both ways to see.) B: Static Structural

(ANSYS)

Static Structur ai Time: 1. s

II Frictionless •

Support

Force: 50000 N

v

Figure 4-22 Structural Static 'Environment' settings. To complete the model building process we need to specify what result quantity or quantities we would like to have calculated and displayed. In this problem we are most interested in the stress and deformation in the X Axis direction.

ANSYS Mechanical 4-14

Project

EJ

~

Model (84)

,,*

!tl"m.,A'il r.tJ... "'~

B

Geometry Coordinate Systems Mesh

"f8 S~~tic Structural

(85) Analysis Settings

!"",,,,fJ

L.."p~Force

Frictionless suppor~

>O~.Q

El'~' Y,

• ,.

""'r'

Solution Information

Figure 4-23 Solution result options menu, 16.

Solution>

Stress> Normal> Orientation>

Also select Deformation

X Axis

and insert the Directional Deformation in the X Axis. Solution l\lId Deformation • l\lIe Strain • l\lIa Stress

q.

Outline ~

EJ

Project @J Model (84)

!tl'>~

IB',,,, B-

*-

,f8

fl)a Equivalent (von-Mises)

EJ

Principal

.fi'Q. Frictionless Support

,~

Solution (86) ",.

lila Middle Principal

eO'

Coordinate Systems

"'Mesh Static Structural (85) ,",t;l AnaiysisSettings Force

;.-"Pot

fl)a Stress •

"0" Maximum

Geometry

y1]]

" ~

Minimum Principal

Solution Information NormalStress

~

Directional Deformation

lila Maximum Shear lila Intensity

~

Notmal

Details of "Normal Stress

B Scope ScopingMethod

$a Shear

Geometry

lflIa

Vector Principal

lflIa Error

q.

n

El

IGeometry Selection IAll Bodies

Definition

Type

INormal Stress

Orientation

IX

Axis

~

Figure 4-24 Select X-direction normal st ress output.

-

---- I

I

4-15

ANSYS Mechanical I

Notice that Solution, Normal Stress, and Directional Displacement items have lightning bolt indicators meaning that we need to highlight one or the other and select complete the simulation solution. ANSYSWorkbench

17•

to

Solve

(g)

Solution Status

Overall Progress ..

:;

S0Ive

:)

Solve

4

Solving the: rnethemencel model •• ,

The solution progress is shown in the ANSYS Workbench Solution Status window.

Stop Solution

Interrupt Solutlon

Figure 4-25 Solution status.

ITIDProbe

When the solution is found, click on the normal stress to view the computed stress results. 18.

Solution > Stress > Normal Stress (In the graphics window - Right click> View> Front; use the pull-down menu to Show Elements.)

6: Static Structural Normal Stress Type:

Show Undeformed

WireFr ame

@

Show Undeformed

Model

[fi

Show Elements

(ANSYS)

Normal Stress(X Axis)

Unit::MPa

Global Coordinate Time: 1

System

101 ..59 Mall

95.184 62.782 70.36 57.978 45.576

I

33.174

zO.nz 8.3702 -4.0317 Min B: Static Structural (ANSYS) Normal Stress d)( ) Type: Normal stress (tmveraoe X Axis.,....... unit:: MPa "'" Global Co«dinate System Time: 1

101.59

"l!l~IlI••

"l""""I'....

"-;.1!lResults

r"""'..,1 '

MirlirrMn

~'i"i·""~DI •• ~'"

Aver~d Nodal Difference NoM! Fraction EIement:a1 Difference Element~ fr",Uon

MaM

95.05 82.515 69.979 51.444 44.908 32.373 19.838 7.3022 -5.2332 Min

Figure 4-26 X direction normal stress; Averaged Display, Unaveraged Display.

•

Pi 4-16

ANSYS Mechanical

I

The solution for the X direction normal stress shows a maximum value of 107 MPa. This value is well below the material yield stress of 250 MPa, so the elastic solution that we have performed is valid. To check this result, find the theoretical stress concentration factor for this problem in a text or reference book or from a web site. For the geometry of this example we find K, = 2.17. We can compute the maximum stress using (Kt)(load)/(net cross sectional area). Using the net section of the whole bar and total loading of 100 kN we obtain:

ax MAX

= 2. I 7 * F * /[(0.4 -

0.2) * 0.01] = 108.5MPa

The computed maximum value is 107.6 MPa which is less than one percent (assuming that the published value of K, is correct, that is).

error

If we list the solution information we find that I I 3 SOLID186 elements were used in the model. A search of the ANSYS Mechanical Help system shows these to a ..~ Solution (86) 113 SOLID186 be 20 node brick elements. ,..... jJJ Solution Information The maximum B: Static Directional

Structural

deformation

in the X direction is about 0.083 mm.

(ANSY5)

Deformation

Type: Directional

DeFormation(X

Axis)

Unit: mm Global Coordinate System Time: 1

0.083109

Max

0,073875 0,064641 0.055406 Q,lM6172

0.036937 0.027703 0.018469 0,0092344 OMin

Figure 4-27 X direction deformation. Before we move on, let's compute and display the str Insert a stress error in the solution item in the project ~::error 19.

Solution>

Stress>

Error>

Solve

,

-; Solve

Computed results are shown in the next figure.

hs.._iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii

_

estimate for this problem.

4-17

ANSYS Mechanical I 8: Statk: structural (AMSYS) Structural Error Type: structlJ'o!Il Error Unit: mJ Time: 1

0.042548 Max 0.03762 0.033093 0,026365

0.023638 0.01891 O,OtiIS3 0,0094555 O,OO~7281

5.8971e-1 Min

Figure 4-28 Computed structural error estimates. The error estimates shown above can be used to help identify regions of potentially high error in the solution and thus show where the model might benefit from a more refined mesh. These error estimates are used in Workbench automatic adaptive meshing and convergence procedures we discuss later. For now we note that the Structural Errors shown are error estimates based upon the difference between the computed smoothed (averaged) stress distribution for the object and the stresses calculated by the finite element method for each element in the mesh (unaveraged). The data are expressed in an energy format (energy is nonnegative) so that the sign of the difference between the estimated stress and the computed stress does not influence the results. The estimated error is displayed for each element. For accurate solutions the difference between the smoothed stress and the element stress is small or zero, so small values of Structural Error are good. We know the above solution is accurate because we compared our result with tabulated results. The small error estimates shown above reflect this, as do the Averaged and Unaveraged results plotted above. If you want the computed results in a different system of units, just change the units in Mechanical after you've computed the results. In the current problem, for example: Max stress Sx = 107.5 MPa = 16,504 psi Max deflection = 0.083 mm = 0.0033 inches

Units

To improve the accuracy we'll generate a model with more elements. There are many ways to control the mesh in Workbench. In what follows we use one of the sizing options. 20.

Mesh> Details of Mesh > Relevance Center> Medium (Coarse is the default.) Solve again.

• ANSYS Mechanical

4-18

,Outline

(i Project

EJ

--

~ Model (84) 1$J".,jiD Geometry ItI·· '",,* Coordinate ,,~

Systems

Mesh

EJ ..",8 Static Structural (8S)

'"",fa

AnalysisSettings

,..,,fill' FrictionlessSupport ··fl...Force 8".@j Solution

(86)

,

;.".,.AIl Solution Information :,.,,~ ,.....~

NormalStress Structural Error

Details of "Mesh" EJ Defaults Physics Preference

Mechanical

Relevance

o

EJ Sizing Use Advanced SizeFunction ~O:-ff-;:__

':l

Medium IEE~le~m~e~nt~S;iz~e~ rrnitial SizeSeed

....

~c~olarls.e •• Fine

Smoothing

Me ium

Transition

Fast

SpanAngle Center

Coarse

MinimumEdge Length

10,0 mm

~

/

Figure 4-29 Relevance Center mesh settings.

l08.69MaM

0.00064178

96,196

0,00057047

83,702

0,00049916

71.208

0.00042785

58,714

Max

0,00035654

46,219

0,00028523

33,725

0,00021393

21.231

0,00014262

8.7371

7.130ge-5

-3.757 Min

1.0396.-9

Min

Figure 4-30 Stress and error estimates based on a medium mesh. 21.

,

Repeat this process using the Fine Mesh setting.

I

4-19

ANSYS Mechanical I

E1 Sizing Use Advanced Size Function

off ----~ Coarse Coarse Medium

Figure 4-31 Relevance Center Fine mesh settings.

108.82 MaM

1.3248e-S Max

96.303

1.1776e-5

83.79

1,0304e-5

71.277

8.8323e-6

58.764

7. 3603e-6

46.251

5.8882e-6

33.738

4.4162e-6

21.225

2.9441e-6

8.7124

1.4721e-6

-3.80D6 Min

5.9703e-12 Min

Figure 4-32 Stress and error estimates based on the fine mesh. 22.

Let's compute another solution for a mesh that is coarser than the first one. Set the Element Size = 50 mm and remesh. We get the results shown below.

102.69 Max

1.6264 MaM

90,89

1.4457

79.086

1.265

67.282

1.0843

55.477

0.9036

43.673

0.72269

31.869

0.54217

20.064

0.36146

8.2599

0.18075

-3.5444 Min

4.321ge-S Min

Figure 4-33 Stress and error estimates based a very coarse mesh.

These results are summarized in the table below. Note that with the finer meshes we obtain a maximum stress of about 109 MPa. With the very coarse mesh we get about 103 MPa., about 6 percent in error.

----------------- ... 4-20

ANSYS Mechanical

I

Table 4A.l - Results Summary Number of Elements

36 137 511 3182

Maximum Deformation in X direction mm 0.0831 0.0831 0.0831 0.0831

Maximum Stress in X direction MPa 102.7 107.8 108.8 108.8

It is important to note the approximate nature of the Finite Element Method and the convergence of the stress results with mesh refinement as illustrated in the above table. Note that with a coarse mesh you can get results that are in error, only about 6 percent in this case, but don't accept results from an initial mesh without question. (Set the element size to 75 mm, and see what you get.) Also note that the tabulated displacement results show no change to three significant figures indicating that the displacements converge more rapidly than the stresses. This is usually the case. The strains (hence stresses) are the spatial directives of the displacement distributions within the object, i.e., E, == etc.

au/ ax,

We will do two more experiments before moving on. Return to the 50 mm mesh and change the stress plotting option. 23.

Select Normal Stress> Display Option> Unaveraged. Recalculate ~ ~

Norm.1 St re ss Directional Deformation

~

Structural Error

Details of ''Norm
;:a:T:s;:c=op::.===;;;;..-------.; SeopingMethod Geometry r::J Definition

GeometrySelection

B: 5latic Structural (MsYs) Normal stress T""""~_la... q.

......(,~

'"O"~"~~'m

Unit: /lPa

-.n(

•.~

~~-""""JX_)

Coordinot. System

GIob~

Time: I

AU Bodies

Type

Normal Stress

Orientation

X Axis

By

Time

l02.69MaM 90,572 78,449 66.326

Display Time

Last

Coordinate System Colculo!lte Time History Identifier

GlobalCoordinate Syst;' Yes

54.204

42.081 29.958 17,835

8 Integration Point Results

5,7126 Unaveraged

,

Minimum M~xlmum

!!Ilnro~on

-6.4101 Min

A\ler~ged Nod~l Difference Nodal frectlon Element'" Difference Elemental Fraction

Figure 4-34 UnaVeraged stress plot.

the solution.

4-21

ANSYS Mechanical I

The figure above is not much different from the previous stress plot except there are some small contour discontinuities between elements in the low stress region. Let's now use a different finite element. In the mesh details box, drop the element midside nodes. 24.

Select Mesh> Advanced> Element Midside Nodes> Dropped

Details of "Mesh"

B: static Structural (ANSV5)

BIOefaults

IPhysics Preference

Normal stress Type: Normal Stress (Unaveraged) ( X Axis) Unit: MPa Global COOfdinate System Time: 1

Mechanical

o Relevance

o

(3 sizing

I Use Advanced Relevance

Size Function Off Fine

Center

o Element Size

50.0 mm

Initial Size Seed Smoothing

Active Assembly

Transition

fast

Span Angle Center

Coarse

91.204MaH 81.108

Medium

I

Minimum Edge Length

71.012 60.917

.

\lO.Omm

•

,

.

!E~n

40.725 30.629

alAdvanced Shape Checking

SO.821

20.534

Standard Mechanical

10.438

Dropped Pro ram Controlled

0.34231

Min

Ke t

Figure 4-35 Stress results found using 8-node brick elements. In the figure above note the maximum stress is only 91 MPa (a 13 percent error), and the stress contours are discontinuous at many element boundaries. We should not have a discontinuous stress distribution in a uniform solid. What's up?

,

I

,,,

,, ,

,I

" ..........

..........

.. ... ~- -"

Figure 4-36 20 node and 8 node solid elements.

The previous results were all calculated using brick elements with midside nodes, giving 20 nodes per element. These last results were found using bricks with nodes only at the corners, 8-node elements. Higher order elements (those with midside nodes) generally give better results because of the better representation of curved geometry and of the

4-22 ANSYS Mechanical

I

displacements, strains and stresses within the element. That's what we see here. Note also that if you plot the averaged stress display for the 50 mm coarse mesh you get a misleadingly smooth display, but the results are still in error by 13 percent. At the completion of the solution, the project schematic shows all items checked off in the Static Structural matrix as shown below.

Geometry

Static Structural (ANSYS)

Figure 4-37 Project Schematic after solution. 25.

Save your work and close the T4A Workbench Project.

The files associated with this project are shown in figure below, T4A.wbpj is the Workbench project file, and the T4A files directory c tai th . h sown. on ins e supportmg files as

~HA,Wbpj El

e:. HA files 8

i:J dpo

Geom

i:J DM

EJ

CJ global SD.

13

t::l SYS

i:J SYS

i:J ENGD i:J MECH

CJ userJiles

Figure 4-38 Files stored after Workbench P , rOJectT4A has been closed. Take a minute to verify the file structure and not th h . required . t e me diIUm mesh model. More space may be e at ' about '. 3 MB s torage IS for duri I' required If Illterm di urmg so ution. It may also be costly to rno th e late files are created problem is being solved. ve ese files around a network as the

ANSYS Mechanical I 4-4

4-23

TUTORIAL 4B - PLATE WITH CENTRAL SQUARE HOLE

Suppose we take the plate of Tutorial 4A and replace the circular hole with a 200 mm square hole. The upper right quadrant of the model is shown below. 1.

Open a new Workbench Project; create the model shown below and save as T4B.

r.---~____

I•

--500.0UU

rI

100.000

Pb

200.000

J

Fignre 4-39 Plate with square hole; dimensions in mm.

2.

Start a new Static Structural Analysis using the quadrant of a plate with a square central cut out. Share Geometry and Double Click Model to start Mechanical.

...

...

A

'"

2 Geometry

~

B

2

4

Model

"'~.4---

5

Setup

'S>

6

Solution

7

Results

3

Ii!J ~

.~

Static Structural

Figure 4-40 Project schematic.

3.

Mesh> Generate Mesh The next figure shows the default mesh for this problem.

p ANSYS Mechanical

4-24

~

, t--

r-t--

-

"..,

'" '"

'.

t-r-

..

f-.~

...

t-rt-

r-r- r-t-

r-r-

,.~

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~t-r-~

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t-

t- ~

N

t-t-~N r-r-:; . f-. ""·,·1:;t-I-H ..,..

Figure 4-41 Default mesh for the plate with square hole. The default mesh consists of 136 brick elements as shown above. 4.

Apply the displacement

bonndary conditions and loading as in Tutorial

T4A.

Include the X direction normal stress in the computed quantities. 5.

Solution> X Axis

6.

Solve

Stress> Normal> Details of "Normal Stress" > Orientation>

-J Solve

s: Static Structural

and view the normal stress solution. Also click the Max icon.

(ANSYS)

Normal Stress Type: Normal Stress (X AXis) Unit: MPa

Global Coordlnete System Time: 1

72.301 MaN 63.138 53.976 44.813 35.65 26.487 17.324 8.1614 ·1.0014 -10.164 Min

Figure 4-42 Normal stress in the X di ti . tree Ion. 7.

Right click and select the front view. The avera ed s maximum stress of around 72 MPa. g mooth stress contours show a

I

ANSYS Mechanical

72.301

4-25

I

•

Insert

MaN

63,138 Isometric View

53,976

I-+-+-I--+-+-l--+--t-ti ~~Set I-+-+-+-+-+-+-+-I-H A 1--1--1--+-+-\-+--+-1-11 ~ ZoomToFit

44,813

Restore Default

35,65 26.487 17,324 8,1614 -1.0014 -10.164

Min

Figure 4-43 Normal stress for 25 mm elements. The default mesh consists of elements that are 25 mm by 25 mm and 10 mm thick. Suppose we reduce the element size and examine the effect on the computed stresses, In the outline tree click on Mesh, then in Details of "Mesh" change the element size from 25 mm to 10 mm,

8.

Mesh>

Details of "Mesh"

9.

Element Size> 10 mm Details of "Mesh" ----

q

-

8 DeFaults physics Preference

Relevance 13 Sizing Use Advdnced Size Functi~

RelevanceCenter

Off __

~rse IO,Omm

Initiai Siza Seed

Act~

Smoothing

Medium

Transition

Fast

Span Angie Center

Coarse

MinimumEdge Length

IO,Omm

-AC-.......j

Assembly

Itl Innation

ctJ Advanced I:!:l Pinch I±I Statistics

Figure 4-44 Set the element size. 10.

Right click Mesh> Generate Mesh

4-26

ANSYS Mechanical

The new mesh with 900 elements is shown below. 86.409MaH

75.236 64.062 52.889 41.716 30.542 19.369 8.1956 -2.9778 -14.151 Min

Figure 4-45 Normal stress for 10 mm elements

11•

S 0 I ve

and view the normal stress solution.

-; Solve

The computed maximum normal stress is 86.4 MPa, an increase of about 20 percent. Now reduce the mesh size to 5 mm. This creates a 7200 element mesh.

107.79MaK

93.815 79.845 65.874 51.904 37.934 23.963 9.9931 -3.9772 -17.947 Min

Figure 4-46 Normal stress for 5 rnm elements. The computed maximum normal stress is 107.8 MPa, an increase of around 25 percent. Finally, reduce the mesh size to 3 mm, producing a model with over 41,000 elements. 12.

Details of "Mesh" > Element Size> 3 mm

13

A

.

, . Sol gam ve

} Solve

d vi h an view t e norma] stress solution.

I

ANSYS Mechanical

4-27

I

129.29 Max 112,5 95,706 78,912 62,117 45,323 28,529 11. 734 -5,0601 -21.854

Min

Figure 4-47 Normal stress for 3 mm elements. The newly computed maximum normal stress in the X-direction is 129 MPa, an increase over the previous value of 20 percent. So, what is happening? The behavior of the maximum stress results we just computed is due the stress singularity at the corner of the square hole. The corner has a zero radius of curvature where the two edges meet, and as the radius of an interior corner or other notch approaches zero, the computed stress approaches an infinite value. If the material is ductile and the loads are static, the high stresses at this location may not be of concern in the actual use of the part. If the material is brittle or the loading is repetitive (fatigue situation), then it is very important to model the actual geometry and thus determine the correct stress value in the vicinity of the notch. During manufacture of a real plate it would be difficult to make the edges of the hole meet with a zero radius at the corner. Or it may be that a specific corner radius is required for the proper function of the part. Suppose for our plate the actual corner radius is 15 mm. Make this geometry change in the model of the plate with the solid modeler you are usmg.

14.

Return to the Project Schematic and double click Geometry. Working in DesignModeler we will add the fillet radius to the plate with the square hole. (If you are using another modeler, modify the geometry in that solid modeler.)

...

A

1

JJ"

2

\llll

Geometry Geometry

../

"

Figure 4-48 Project schematic view.

------------------------4-28

15.

ANSYS Mechanical

Select the Edge Filter @, click the interior Corner Edge and then select Fixed , Radius Blend ~ )j,1

A. Geometry

Concept:

Tools

View Help

P1,~

'!l !:l.

.

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xYP

.,

Ifl)

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DeslgnModeler

l:_~.:~ ill 1 >I- N••

Enter 15 mm > Generate OJ

Blend

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Figure 4-49 Part in DesignModeler.

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'i'''T.i~c.:::::;::---.:!.'

Q,pl;"

r,;. Details or fBlend3

Rxed-:RcdIusEi;;d 'F6Ieo:!3 : rol, RdJs(>0) "Is,;;;Geomet:rL _.

1 Edge

Figure 4-50 Updated DesignM d I

o e er geometry.

".

~

I

...

4-29

ANSYS Mechanical I Now update the Static Structural Analysis model to the new geometry. 16.

Return to the Project Schematic view. Left click on the small blue triangle in cell B4, Model.

...

... 2

Eli)

Geometry Geometry

../

.. -........"

2

"'-

3 4

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B

Enginee~ingData

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ri)··~~d~i·····"····"·····_·······~··~~ ....................................................... ,

5

Setup

6

@

Solutio

7

@

Results

Upstream data has been added or updated. Right-click and choose Refresh or Update to read the updated data. You can also select Edit to perform a Refresh and open the model in the 1\'1echanicalapplication.

Static S

Systems and Cells ANSYS Workbench Figure 4-51 Model information screen. 17.

Right Click in cell B4, Model and select Update.

(M)

Edit ...

I~ Duplicate

-~

Transfer Data To New

-

II

Update

Ii!

Refresh

14

Clear Generated Data Reset

~

Rename Properties

-

-

-

Quick Help

Figure 4-52 Update the model. After the update is complete, return to the Static Structural

Mechanical screen.

ANSYS Mechanical

4-30

18.

I

Reset the mesh Relevance to Coarse and en t er 0 for Element Size to reset it to Default. 5izing Use Advanced Size Function

Off

Relevance Center

Coarse

Element Size

Default

Initial Size Seed

Active Assembly

Smoothing

Medium

Transition

Fast

Span Angle Center

Coarse

Minimum Edge length

10,0 mm

-

Figure 4-53 Reset element size. The project now IS " . . updated;, the material load and frictionless supports remain the same; the analysis proceeds as bel" ore.

Structural (ANSYS)

B; statk

NoonaI

-) Solve

Stress

Type: Normal Stress ( X Axis ) Unit: MPa Global Coordinate

System

Time: 1

100.73 Max 89,127 77,528 65,929 54,33 42,731 31.131 19,532 7,9333 -3.6658 Min

Figure 4-54 Default mesh for modified geometry. The computed maximum stress associated with the 15 mm comer radius is about 101 MPa. We can control the accuracy of the solution manually as we did in previous examples or we can request an automatic iterative solution process to be employed that will use models with successively smaller element sizes while monitoring the change in the requested solution quantity. This is essentially an automation of what we did manually earlier.

4-31

ANSYS Mechanical I Select maximum Normal Stress as the quantity to monitor during iterative solution. 19.

Right click Normal Stress> Insert> Left click Convergence ~

..ret

static 5tructural (B5) (,,,,,.1~ Analysis Settings

~.. ".,[email protected].

Frictionless Support

.~ ... force El "..@!J Solution

(06)

!".,.....m ..5°iiluiitiionijlilnfiormation "c!ll"Structural Err i ~

•

Stress Tool

==

Deformation

Export

Strain

~~ Duplicate

Stress

~~ Duplicate Without Results

Energy

~Copy

Linearized Stress

j(,

Cut

Fatigue

,,£j Clear Generated X. Delete

Data

Contact Tool Probe

61ThRename

alb

Rename Based

on Definition

Coordinate Systems

~

• • • • • • • •

Convergence

o Alert

/

1:. User Defined

Result

Ii: commands Figure 4-55 Insert convergence criterion. Define the allowable change in the maximum Normal Stress between solutions. 20.

Details of "Convergence" > Allowable Change> 1 percent El ~

Solution (06)

)]J Solution

InfOl'm~tion

8. ..... e Normal stress 14 oI£lF-iJQJ6i4. 4

¥

./'

..,.e StructUf al Error

0

fDetaJ1sof "ConverQWIce" EJ Definition

__

~ --_.ladi _.;7axmum

-

AUowable Change 1. %

_

-

J

.-

8 Results lllsl::CMn<;1e converged

1°·%

~'

[No

Figure 4-56 Allowable change in the normal stress. Define the default number of mesh refinements and depth (refinement gradations).

c 4-32 21.

ANSYS Mechanical Solution>

Max Refinement Loops> 4; Refinement Depth> -~.

B'~'

•

,

!

S ~

;,

Solution Information Normal Stress

....[2] ~

2

Convergence

Structural Error

Details of "Solution (86)" B Adaptive

Mesh Refinement

Max Refinement loops

4,

Refinement Depth

2,

Figure 4-57 Adaptive refinement parameters.

22.

Right click Solution or Normal Stress> Solve

-) Solve

O v er all Progress",

-

Evaluahng results".

Interrupt Solution

Figure 4-58 Solution status. 23.

Once the solution process has finished, click on Convergence.

The convergence results shown in the next figure are displayed. The model is refined from 1088 nodes and 135 elements to one with 69,225 nodes and 46,623 elements. The maximum normal stress in the X-direction changes from 101 MPa to about 123 MPa, a total change of about 22 percent. Note that the repeated solution continues until the change in successively computed maximum normal stress values is less than I percent as requested. See the next figure. You will not want to use this convergence process for problems you are very familiar with, but in certain cases it is a very useful tool.

I

4-33

ANSYS Mechanical I

122.99MaM 109.18 95,364 81.55 67,736 53.922 40.108 26.294 12,48 -1.3343 Min

123

T----~-----:-----=:;;::::=::::::==1

120

, ", III III

'

III ./::l1l2 - •••• , ••.•••

___

w

,

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16

:

E 108

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o z 104 101 ...

=-

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3

2

1

5

4

solution Number

1 NormalStress (MPa) I Changet%) I Nodesl 1 2 3 4 5

100,94 103.13 120.52 122.02 122.99

2.1493 15,554 1.2363 0.79053

1088 4569 9290 26588 69225

Elements 135 2482 5603 17241 46623

Figure 4-59 Final mesh and stress convergence history. The convergence path could be altered by the choice of the mesh refinements. A uniform mesh refinement followed by a local refinement using this convergence object will likely produce different intermediate results. Experimentation and experience are important. Note also that for ease of meshing, the automatic meshing process changed to ten-node tetrahedron 24.

elements.

Save your work.

4-34

4-5

ANSYS Mechanical

I

SUMMARY

The tutorials in Chapter 4 illustrate basic concepts of stress computation with Structural Static Mechanical simulation coupled with ANSYS DesignModeler or another solid modeler. We note that computed values must be examined carefully to evaluate their accuracy and that manual or automatic convergence studies can and should be used to insure quality of results. Don't necessarily accept the results of the first mesh you try. ANSYS Elements used in this chapter: SOLID186, Homogenous Structural Solid 8-node and 20-node bricks as well as IO-node tetrahedral, pyramid and prism variations as required by automatic meshing of volumes.

Figure 4-60 Elements used in this chapter. In the next Chapter we will extend these ideas to more campi rt d i t d ddi . I' I' ex pa s an III ro uce a mona srmu arion modeling options.

4-35

ANSYS Mechanical I 4-6

PROBLEMS

Throughout the remainder of the book express your computed results using 3 to 4 significant digits accuracy unless otherwise indicated and convert computed results so as to be able to present results in both systems of generally accepted units for engineering work. That is, work the problem using the units in which it's defined, show the computed results in those units, and convert the results so that you can present answers in both MKS (mm KS) and IPS (FPS) systems. See Tutorial IA. Always show the meshes you use in your solution, and for problems in stress analysis, it's also a good idea to first plot UNAVERAGED results as a quick visual check on accuracy; again see Tl A. 4-1

Consider a thin structural steel plate as shown below. Compute the maximum normal stress in the horizontal, X direction if 100 kN tensile load is applied to the left and right end surfaces. Compare your result with the value you compute using tabulated stress concentration factors for this geometry. If necessary, insert a convergence control to help access the accuracy of your solution. Use the three planes of symmetry this problem has and analyze only one eighth of the solid. Put frictionless supports on the planes of symmetry and apply one-fourth of the load, that is (100/4) kN. See Tutorial 4A, step IS. Present both Averaged and Un averaged Stress results plots. If you have time, use only two planes of symmetry, apply one half of the load as we did in Tutorial 4AI. Compare your results to those obtained using three planes of symmetry.

/R

=50mm

~ 100kN

400 x 200 x 10 mm Figure P4-1 4-2

Figure P4-2

Place a 25 mm diameter hole 100 mm to left and to the right of the vertical centerline but on the horizontal centerline of the part in Problem 4-1. Find the magnitude and location of the maximum normal stress. Compare this result to the theoretical maximum stress in the plate without the added holes using tabulated stress concentration factors to determine the theoretical result.

4-36

4-3

ANSYS Mechanical

I

Consider the long, thin structural steel beam shown below, fixed at one end, free at the other. Apply a pressure of 200 psi on the upper edge. Compute the vertical deflection at the free end and the maximum bending stress at the top edge at the middle of the beam. Look up the theoretical solution in your solid mechanics book and compare your FEM results with the results you can compute from beam theory.

p = 200 psi

/ 8 X 1 inches 1 0.25 thick Figure P4-3 4-4

Repeat the problem described in Problem 4-3 but make the beam 1 x 1 x 0.25 inches. Slender beam theory no longer applies to this geometry. Determine the theoretical solution for the end deflection o~ this cantilever beam from solid mechanics theory and compare WIth your FEM result. Comment on the differences. Figure P4-4

4-5

Repeat the problem described in Problem 4-3 but drill a 0 25' h di hit the center ofthe beam. . me iameter 0 e a

p = 200 psi

/

o 8 X 1 inches 1 0.25 thick Figure P4-S 4-6

The central bore of the indexing whe I d h The thickness is 0.5 inch and th de.an t e 8 slots are all 1.0 inch in diameter. .. •. e iameter D ~ 4' h F' d h . principal stram 10 pressurized indexl . me es. m t e maximum I h exmg slot If the rd gnore t e strains in the completel fi d app te pressure is 5,000 psi. decimal value and also report th Y Ilxe. central hole. Report the calculated d e resu t 10 terms f . compute value computed multiplied b 106 0 micro-strain, that is, the y . See figure below.

4-7

Repeat problem 4-6 but use a vertic I 1 . fri ti I a pane to slic ff h a If of the geometry and put a fie IOness support on the exposed leo pane of symmetry.

ANSYS Mechanical

4-37

I Pressure

I~

D

~I Figure P4-6 and Figure P4-8

4-8

A 20 inch diameter cylinder has an 8 in square hole with 1.0 inch radius comer fillets. The thickness is 0.75 inch. Find the maximum values for von Mises stress, principal stress, shear stress, and displacement if the front and back surfaces have frictionless supports (condition of plane strain) and the interior has a pressure of7500 psi.

4-9

The structural steel frame shown is fixed at its base and loaded with a pressure of P = 2 MPa as shown. Cut a sectiDnplane through the vertical segment at point a half way up. Draw a free body diagram showing the forces and moment acting on the cross section of the upper portion. Use a hand calculation to compute the Bending Stress +/- Axial Stress at the left edge point a. Also use ANSYS Workbench to compute the maximum vertical stress and compare your results.

10mm

125

1 140 I

fixed base

Figure P4-9

=-::::~~B

---Sinch

Figure P4-10

4-38

ANSYS Mechanical

I

4-10 The equilateral triangle is 8 inches on each side, and the thickness is 1 inch. The 0.5 inch diameter holes are symmetrically placed radially 3.5 inches from the center. The part is supported at holes A and B with cylindrical supports, fixed radially and axially but free tangentally to allow rotation. A horizontal load in the mid plane of the plate of 15,000 Ibf is applied to hole C. Find the magnitude and location of: a. max von Mises Stress b. max Principal Stress c. max Principal Strain d. max Horizontal Displacement 4-11 Solve the statically indeterminate, axially loaded bar problem described in ANSYS verification manual VMMECHOOI. 4-12 Solve the plate with central hole problem described in VMMECH002.

>