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.
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Placed Features, Assembly
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2-3
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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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Placed Features,
2-4
Assembly
J ~~/ Generate
6.
Click Generate
7.
Select Plane4 > Then click on the Look at icon to view the Plane4
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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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ave your part u ing a new name. I.
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File> Save As > Tutorial2B
Set the selection filter.
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2.
election Filter: Edges
J.
elect the inside edge ofthe part.
Figure 2-8 Select the edge. 4.
Create>
Fixed Radius Blend
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Placed Features, Assembly
1
File
Create
Concept
Tools
2-7
View Help
*- New Plane
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Body Operation
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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!
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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
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Tutorial2E
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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
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Chamfer1 Pattern! 1 Part, 1 Body
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Sketching MOdeling
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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
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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
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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.
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L2
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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
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Details of
-,
Sketch6
sketch
Sketch6
Show Constraints? No
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Dimensions: 2
EJ
Edges: 1 Full Cirde
...............
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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> 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 :
•
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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
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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)
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! 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
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B
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XYPlane Sketch!
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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.)
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'" @ A: Geometry
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XYPlane
: ',,*,
ZXPlane
L "
YZPlane 0 Parts) 0 Bodies
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Tools
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,
lines From Points
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lines From Sketches
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lines From Edges
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Details View
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..... Split Edges
~
Surfaces From Sketches
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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
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6.
Figure 3-24 Generate Line Body. Concept> Cross Section> Channel
..
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Cross Section
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_ 72.000
__ Surf aces: From Edges:
5.
···
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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
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Rectangular
•
Circular
3.000
o Circular Tube
W2
~ Channel Secbon
.... Split Edges
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Surfaces From Edges
C2I €J
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1.000
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T Section
A
Hat Section
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Cross Section
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tl
Figure 3-25 Choose Channel Section.
Tfee Outline B.,.
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8
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ZXPlane YZPlane line!
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120000 Sketching
Modeling
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V1
Details View
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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
....
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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
....
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Start ANSYS Workbench, begin a new Project.
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Help Meshing Utilities
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Mechanical APDL (ANSYS) 14.0 Mechanical APDLProduct Launcher 14.0
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Worl Component Systems to initiate the geometry object in the Project Schematic. See the next figure.
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""-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",,,,_ $...
""Show"'""
Mesh:)~
~Mesh
Oulh
..
tJ
;;_.
roo roo e-
ibt ~
~ ,;:
HEdgoC_ • MeshCortrli ... .,-
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e.
@. ~
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:;:,
e
A· A· A· A· A· " H I-Ir""",_
lb,
_ y
. ProJee:t
'" iii M....
l..)
static """ ....e
Systems
Structural (85)
....C3 Analysis Settings
}il11 FrictJonless Support
fl..Force Fi ~
SotuUon (86)
Figure 4-12 Plate quadrant in Static Structural Mechanical module. Since the geometry was. created using mm, the length units for the simulation should be mm also. Check the units usmg the Units pull-down menu Unit M . N s, mY, rnA) . m s> etnc (mm, kg, ,
6.
Highlight Material in the Details of "T4A" wind
ow.
-----------------1'4 4-9
ANSYS Mechanical I
7Units
Tools
I
Help
Metric (m, kg) NJ
S,
I :)~olve
(J
•
t$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"
$"".,)iSt
Geometry
[£- .....
Coordinate
8·
Systems ~---j
.,.s ~~:-_I"_,e_rt -\ ,;
_
Update
Preview Show :) Create ________
Pinch Controls
Loads> Force.
Environment ~ ....Inertial ... @"toads ... @" Supports ... ll-
Outline
la Project 8 ~ Model (04) [fJ
l±}-
.;fjI 0/*
I
@... Pressure
Geometry Coordinate
Systems
~Mesh
8
£:1 Static Structural (05) -
,,{;j,
EJ
@"Loads • @. Supports.
./
@" Hydrostatic Pressure
¥'
!d
Force
Analysis Settings
@.. Remote Force
?fi1 Solution (06) '. 'AIl Solution Information
'tI,
Bearing Load
Figure 4-18 Structural loads menu. ~
Be sure that the Face selection filter is highlighted @ and click on the area on the right end of the solid model.
·-------------------~ ANSYS Mechanical
I
4-12
12.
Geometry>
Apply (Note: It's easy to forget this step.)
13.
Define (the force) by (X Y Z) Components, X Component ~
.
_._,-,
'-~=:iellt-'~~ ~@.. ~~7lSi~s:-:-~·ii~.c~Olid~·it~~-;~:.::$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 ''NormI- N••
Enter 15 mm > Generate OJ
Blend
~""'Ildt
__
sm,tLoft
~.Tl"in/Surface
I--~---·_-
!.~i.i"!'
14 VaMbie
I < Vertex
I
Radius Blend
Blend
~Ch.>mf".
_
J:::~''''' Sketc •
Boolean
""..,j .. "',
J %i.
III~face Delete
'do< """.
,-'-----
Figure 4-49 Part in DesignModeler.
1';J IIExtrlXle
'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
I. ij)})
B
Enginee~ingData
../
..
Geometry
../
..
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
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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 ~
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static 5tructural (B5) (,,,,,.1~ Analysis Settings
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Stress Tool
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Deformation
Export
Strain
~~ Duplicate
Stress
~~ Duplicate Without Results
Energy
~Copy
Linearized Stress
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Cut
Fatigue
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Data
Contact Tool Probe
61ThRename
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Rename Based
on Definition
Coordinate Systems
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Convergence
o Alert
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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)
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InfOl'm~tion
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