dm 11 ch06 concept.ppt - ttu.eeinnomet.ttu.ee/martin/mer0070/wb/dm11/dm_11_ch06_concept.pdf ·...

Chapter 6

Concept Modeling

Chapter 6

Concept Modelingp gp g

May 11, 2007© 2007 ANSYS, Inc. All rights reserved.

ANSYS, Inc. Proprietary Inventory #0024966-1

Training Manual

Concept ModelingContents

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• Concept Modeling• Creating Line Bodies

M dif i Li B di

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• Modifying Line Bodies• Cross Sections• Cross Section Alignment• Cross Section Offset er• Cross Section Offset• Surfaces From Lines• Surfaces From Sketches• Edge Jointsg• Workshop 6-1, Line and Surface Bodies


Inventory #0024966-2

ANSYS, Inc. Proprietary

Training Manual

Concept ModelingConcept Modeling

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• The features in the Concept menu are used to create and modify line bodies and/or surface bodies which become FE beam or shell gnM

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models. • To begin Concept Modeling, you can either:

– Create line or surface bodies using the features in the Draw toolbox to erdesign a 2D sketch and/or generate a 3D model– Use the Import external geometry file feature

• Line bodies can be created using the concept modeling tools:– Lines from points– Lines from sketches– Lines from edges

• Surface bodies can be created using the concept modeling tools:– Surfaces from line bodies– Surfaces from sketches




– Surfaces from 3d edges

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Concept ModelingCreating Line Bodies

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• Lines From Points:– Points can be any 2D sketch points, 3D model vertices or Point Feature (PF)

i t

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points. – A point segment is a straight line connecting two selected points. – The feature can produce multiple Line Bodies, depending on the connectivity

of the chosen point segments. erp g– The Operation field allows Add or Add Frozen choices for line bodies.




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Concept Modeling…Creating Line Bodies

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Example of “Line From Points” using 2d points from a rectangular sketch.

2 points are chosen to define a diagonal line body. The green line indicates proposed line segment

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indicates proposed line segment.

Apply the selection then Generate. The Line body is displayed in blue.

er

Point 1Line Body




Point 2

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• Lines From Sketches:– Line bodies created based on sketches and planes from faces gnM

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– Multiple Line Bodies may be created depending on the connectivity of the edges within the base objects

– Select sketches or planes in the feature tree then “Apply” in the detail window– Multiple sketches, planes, and combinations of sketches and planes can be erMultiple sketches, planes, and combinations of sketches and planes can be

used as the base object for the creation of line bodies




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Example of “Lines From Sketches”.

Sketch created as input for Line Body creation. gnModele

“Lines From Sketches” is chosen:

• Highlight sketch in tree

• Apply as base object in Detail window er




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• Lines From Edges:– Creates line bodies based on existing 2D and 3D model edges gnM

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– Can produce multiple line bodies depending on the connectivity of the selected edges and faces

– Can select edges and/or faces through two fields in the detail window then “Apply” ery




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Example of “Lines From Edges”. 3D solid created as input for Line Body creation.

“Lines From Edges” is chosen: gnModele

• Select faces on model. Face boundaries will become line bodies (alternately select 3d edges directly).

• Apply as base object in Detail window

• Note: in this case 2 line bodies are created due to the edge connectivity er• Note: in this case 2 line bodies are created due to the edge connectivity.




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Concept ModelingModifying Line Bodies

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• Split Line Body:– Splits line body edges into two pieces gnM

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– Split location is controlled by the Fraction property (e.g. 0.5 = split in half). – Example:

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Selected line Fraction = 0.5 Fraction = 0.25




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Concept ModelingCross Sections

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• Cross Sections:– Cross sections are attributes assigned to line bodies to define beam properties

i th FE i l ti

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in the FE simulation– In DM, cross sections are represented by sketches and are controlled by a set

of dimensions• Note: DesignModeler uses a different coordinate system for cross sections than the erone used in the ANSYS environment (described later)




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Concept Modeling…Cross Sections

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• Cross sections are selected from the Concept menu• A cross section branch is inserted in the tree where each chosen gnM

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cross section is listed

er

Concept menu

Display Tree

Cross Section menu




menu

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• Highlight the cross section in the Tree to modify dimensions in the Details window

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• Dimension Editing– Cross section dimensions can be repositioned via a RMB and choosing Move gnM

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Dimensions

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• Assigning a cross section to a line body:– Highlight the line body in the Tree gnM

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– A cross section property appears in the detail window– Click in this field and choose the desired cross section from the drop down list

er




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• A user integrated section can be defined in DM• The cross section is not sketched, rather the cross section’s properties are gnM

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placed in the details window

er

• A = Area of section.

• Ixx = Moment of inertia about the x axis.

• Ixy = Product of inertia.y

• Iyy = Moment of inertia about the y axis.

• Iw =Warping constant.

• J = Torsional constant.

• CGx = X coordinate of centroid.

• CGy = Y coordinate of centroid.

• SHx = X coordinate of shear center.




• SHy = Y coordinate of shear center.

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Concept ModelingCross Section Alignment

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• As shown below in DesignModeler the cross section lies in the XY plane:• Cross section alignment is defined by: gnM

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– A local or cross section +Y direction• Default alignment is with the global +Y direction unless that would result in an invalid

alignment in which case +Z is used– Note: In the ANSYS Classic Environment, the cross section lies in the YZ plane erote t e S S C ass c o e t, t e c oss sect o es t e p a e

and uses the X direction as the edge tangent. This difference in orientation has no bearing on the analysis.

Y

Edge

Cross Section




Edge Tangent

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Concept Modeling…Cross Section Alignment

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• A color code is used to indicate cross section status for line bodies:– Violet: no cross section assigned gnM

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– Black: cross section assigned with valid alignment– Red: cross section assigned with invalid alignment

• The line body icons in the tree have similar visual aids:Green: cross section assigned with valid cross section alignment

er– Green: cross section assigned with valid cross section alignment– Yellow: no cross section assigned or default alignment– Red: invalid cross section alignment




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Concept Modeling

…Cross Section AlignmentTraining Manual

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• Checking alignment can be done graphically using the View menu: gnM

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View menu:– Choose “Show Cross Section Alignments”

• Green arrow = +Y, blue arrow = edge tangent of cross sectionOr choose “Cross Section Solids” er– Or choose Cross Section Solids

+Y

Edge Tangent




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• Because a default alignment is chosen cross section orientation will almost always need to be modified. There are 2 methods for cross section alignment selection and vector:

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alignment, selection and vector:– The selection method uses existing geometry (edges, points, etc.) as alignment

reference– The vector method uses input according to X, Y, Z coordinate directions erp g

• For either method a rotation angle can be input and/or the orientation reversed




Selection Method Vector Method

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• Modifying the cross section orientation by vector:

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Switch to “Vector” alignment mode

erEnter the desired coordinate values

E t t tiEnter rotation angle if desired

ReverseReverse orientation if

desired




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• Modifying the cross section orientation by selection (several examples follow): gnM

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1. Select the line body to be aligned in graphics window

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3. Select the geometry to be used for alignment




2. With “Selection”method active click in the alignment field

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Alignment using lines or axes.

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Line chosen for alignment

Y er

Axis chosen for alignment

Edge Tangent

Y




Edge Tangent

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Alignment using face normal. gnM

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Alignment Faces

Y

Y




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Alignment using sketch points.

Note: the order of point selection determines cross section alignment

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Note: the order of point selection determines cross section alignment.

2D points1 er

2

Selected Line BodyY

Edge Tangent




Edge Tangent

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Concept ModelingCross Section Offset

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• Cross Section Offset:– After assigning a cross section to a line body, the Detail property allows users to

if th t f ff t t ith th ti

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specify the type of offset to use with the cross section: • Centroid: The cross section is centered on the line body according to its centroid

(default)• Shear Center: The cross section is centered on the line body according to its shear

center

ercenter– Note the graphical display for centroid and shear center appear the same however,

when analyzed, the shear center is used• Origin: The cross section is not offset and is taken exactly as it appears in its sketch

• Examples next page




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Concept Modeling…Cross Section Offset

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Origin offset (no offset)

er

Line Body

Centroid/Shear Center offset

Line Body with cross section displayed




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Concept ModelingSurfaces From Lines

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• Surfaces From Lines:– Creates surface body using line body edges as the boundary gnM

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– Line body edges must form non-intersecting closed loops– Each closed loop creates a frozen Surface Body– The loops should form a shape such that a simple surface can be inserted into

the model: erthe model: • Planes, cylinders, tori, cones, spheres and simple twisted surfaces

Planar surface Twisted surface

Details window:Flip surface normals




• Flip surface normals

• Input thickness which will be transferred to the FE model

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Concept Modeling…Surfaces From Lines

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• Notes on surface from lines:– A line body with no cross section can be used to tie together surface models. In

thi th li b d t l h i t i ti

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this case the line body acts merely as a mechanism to insure a continuous mesh at the surface boundaries.

2 S f B di

er2 Surface Bodies

Li B d ( ti ) Result is continuous FE mesh




Line Body (no cross section) Result is continuous FE mesh at surface interface

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Concept ModelingSurfaces From Sketches

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• Surfaces From Sketches:– Creates surface bodies using sketches as boundaries (single or multiple sketches

OK)

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are OK)– Base sketches must be closed profiles which are not self intersecting– May choose to “Add” or “Add Frozen” operations– Can reverse normal direction “No” in Orient With Plane Normal field erCan reverse normal direction No in Orient With Plane Normal field– Can enter thickness which will be used in creating the FE model




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Concept Modeling…Surfaces From Sketches

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for operation

Click in the “Base Objects” field

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Select the desired sketch from the treesketch from the tree then “Apply”

Select a portion of the desired




Select a portion of the desired sketch in the graphics window then “Apply”

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Concept ModelingSurfaces From Edges

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• Surfaces from Edges:

• Creates surfaces from existing body edges gnModele

• Can be solid or line body edges.

• Edges must produce non-intersecting closed loops.

• Example: erExample:

Existing solid body edges are N f f b d d




Existing solid body edges are selected for new surface boundary.

New, frozen, surface body generated (note, solid body is hidden).

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Concept ModelingSurfaces Patch

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• Surface patching attempts to fill gaps in the model.

• Uses similar healing methods as face delete (natural and patch). gnModele

• Complex gaps may result in multiple surfaces being created to fill them.

• Example:

er

2 holes selected for patching Two patches created using multiple




2 holes selected for patching Two patches created using multiple surfaces

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Concept ModelingEdge Joints

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• Edge Joints are the glue that holds together bodies where a continuous mesh is desired. gnM

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• Creating surface and/or line multibody parts with coincident edges results in automatic creation of edge joints.

• Joints can be created manually where no coincident topology exists. ery p gy




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Concept Modeling…Edge Joints

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• Edge Joints can be viewed by turning on the Edge Joints option in the View menu: gnM

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• Edge joints are displayed in either blue or red. er

– Blue: edge joint is contained in properly defined multi-body part

– Red: edge joint not grouped into the same g j g ppart




No Edge Joint With Edge Joint

Line and Surface BodiesLine and Surface Bodies

Workshop 6-1Workshop 6 1


ANSYS, Inc. Proprietary Inventory #0024966-36

Training Manual

Workshop 6-1, Line and Surface BodiesTraining Manual

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• Goals:– Create a sketch representing beams used to stiffen a panel. gnM

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– Create a line body from the sketch. – Choose a beam cross section to be used and assign it to the line

body.– Create a surface model representing the panel. erCreate a surface model representing the panel.

• >File>New, or Start Page:– Choose to create new geometry– At the prompt, set the length unit to millimeter




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Create a rectangle[Sketch] > Rectangle gnM

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1. Place the cursor near the origin until ‘P’ appears, click then drag to define the rectangle er

Click “>Look At” & “>Zoom to Fit” tool buttons, and Triad ISO Ball as desired.

1




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Dimension the rectangle 600X300 mm as shown

[Sketch] > Dimension > General

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[Sketch] Dimension GeneralHorizontal = 600 mmVertical = 300 mm

Fit the sketch and move erFit the sketch and move dimensions as necessary

[Sketch] > Dimension > Move




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Add 2 vertical lines and dimension as shown

[Sketch] > Draw > Line

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[ ]2. Place the cursor near the top line

until the ‘C’ coincidence constraint appears. Move the cursor to the bottom line until the ‘C’ appears

d ‘V’ i di ti ti l

erand a ‘V’ indicating a vertical constraint.

3. Repeat for second line

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2 3

Apply horizontal dimensions as shown.

[Sketch] > Dimension > HorizontalAdjust Details so all dimensions

are as indicatedare as indicated




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Create a Line Body from Sketch1[Main Menu] > Concept > Lines

From Sketches

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From Sketches4. Select “Sketch1” from the Tree

(click the “+” near the XYPlane to expand that branch if necessary) and

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er“>Details>Apply” it as the base object

5. Click >Generate 4




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Select a rectangular tube type cross section: [Main Menu] > Concept > Cross Section > Rectangular Tube

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Section > Rectangular TubeAfter selection, the cross section is

displayed with its dimensions.

erIn this case we will use the default dimensions.

If desired the cross section Details canIf desired the cross section Details can be changed to modify the cross section.




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With a cross section selected we now need to associate it with our line body. gnM

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y6. Highlight the line body in the tree

and the details shows that no cross section is yet associated with it.[tree] > 1 Part, 1 Body > Line Body er(at bottom of tree)

7. Click in the “Cross Section” field

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8. Choose “RecTube1” from the drop down list

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9. After assigning the cross section to the line body the default display shows the line body with gnM

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p y yits cross section alignment (see right). We can also display the beam with the cross section displayed as a solid.

[M i M ] > Vi > Sh C

er[Main Menu] > View > Show Cross Sections Solids




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The next step is to create the surfaces between the beams. These surfaces will be shell gnM

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meshed in the FE simulation.10. [Main Menu] > Concept >

Surfaces From LinesHold the control key and select the 10 er4 lines shown at right.(or can hold down LMB and sweep

mouse over lines to be group selected)

11 >A l11. >Apply

11




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12. “>Generate” the Surface Body.Note: a frozen surface body is created, bounded by the

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created, bounded by the selected lines

Repeat the previous steps to

12

erRepeat the previous steps to create two more surface bodies

“>Generate” as necessary




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The final modeling operation is to place all the bodies into a single part (multi-body part). gnM

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p ( y p )We must do this to insure that, when meshed, each boundary “recognizes” its neighbor resulting in a continuous mesh. erSet the Selection Filter to “Bodies”. In the graphics window right mouse click and choose “>Select All”All




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With all bodies selected, again right click in the graphics window and choose “Form New Part”. gnM

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By examining the Tree notice a single part has been formed erg pwhich contains 4 bodies.




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• Shown here we have moved to a Simulation environment in Workbench and meshed the geometry.

B i ll b di i t ( i l ) t d l ti it i

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– By grouping all bodies into a common (single) part, nodal connectivity is insured.

er




dm 11 ch06 concept.ppt - ttu.eeinnomet.ttu.ee/martin/mer0070/wb/dm11/dm_11_ch06_concept.pdf ·...

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