Concept%20Modeling

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Concept Modeling

• Chapter 6

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Concept ModelingContents

• Concept Modeling
• Creating Line Bodies
• Modifying Line Bodies
• Cross Sections
• Cross Section Alignment
• Cross Section Offset
• Surfaces From Lines
• Edge Joints
• Workshop 6-1, Line and Surface Bodies

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Concept ModelingConcept Modeling

• The features in the Concept menu are used to
  create and modify line bodies and/or surface
  bodies which become FE beam or shell models.
• To begin Concept Modeling, you can either
• Create line or surface bodies using the features
  in the Draw toolbox to design 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 lines
• Surfaces from sketches

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Concept ModelingCreating Line Bodies

• Lines From Points
• Points can be any 2D sketch points, 3D model
  vertices or Point Feature (PF) 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.
• The Operation field allows Add or Add Frozen
  choices for line bodies.

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Concept ModelingCreating Line Bodies
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. Apply the
selection then Generate. The Line body is
displayed in blue.
Line Body
Point 1
Point 2
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Concept ModelingCreating Line Bodies

• Lines From Sketches
• Line bodies created based on sketches and planes
  from faces
• 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 used as the base
  object for the creation of line bodies

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Concept ModelingCreating Line Bodies

• Example of Lines From Sketches.
• Sketch created as input for Line Body creation.
• Lines From Sketches is chosen
• Highlight sketch in tree
• Apply as base object in Detail window

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Concept ModelingCreating Line Bodies

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

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Concept ModelingCreating Line Bodies

• Example of Lines From Edges. 3D solid created
  as input for Line Body creation.
• Lines From Edges is chosen
• 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.

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Concept ModelingModifying Line Bodies

• Split Line Body
• Splits line body edges into two pieces
• Split location is controlled by the Fraction
  property (e.g. 0.5 split in half).
• Example

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Concept ModelingCross Sections

• Cross Sections
• Cross sections are attributes assigned to line
  bodies to define beam properties 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 one used in
  the ANSYS environment (described later)

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Concept ModelingCross Sections

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

Concept menu
Display Tree
Cross Section menu
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Concept ModelingCross Sections

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

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Concept ModelingCross Sections

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

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Concept ModelingCross Sections

• Assigning a cross section to a line body
• Highlight the line body in the Tree
• A cross section property appears in the detail
  window
• Click in this field and choose the desired cross
  section from the drop down list

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Concept ModelingCross Sections

• A user integrated section can be defined in DM
• The cross section is not sketched, rather the
  cross sections properties are placed in the
  details window

• A Area of section.
• Ixx Moment of inertia about the x axis.
• Ixy Product of inertia.
• 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

• As shown below in DesignModeler the cross section
  lies in the XY plane
• Cross section alignment is defined by
• 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 and uses the X
  direction as the edge tangent. This difference in
  orientation has no bearing on the analysis.

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Concept ModelingCross Section Alignment

• A color code is used to indicate cross section
  status for line bodies
• Violet no cross section assigned
• 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
• Yellow no cross section assigned or default
  alignment
• Red invalid cross section alignment

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Concept ModelingCross Section Alignment

• Checking alignment can be done graphically using
  the View menu
• Choose Show Cross Section Alignments
• Green arrow Y, blue arrow edge tangent of
  cross section
• Or choose Cross Section Solids

Y
Edge Tangent
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Concept ModelingCross Section Alignment

• 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
• The selection method uses existing geometry
  (edges, points, etc.) as alignment reference
• The vector method uses input according to X, Y, Z
  coordinate directions
• For either method a rotation angle can be input
  and/or the orientation reversed

Selection Method
Vector Method
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Concept ModelingCross Section Alignment

• Modifying the cross section orientation by
  vector

Switch to Vector alignment mode
Enter the desired coordinate values
Enter rotation angle if desired
Reverse orientation if desired
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Concept ModelingCross Section Alignment

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

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

1. Select the geometry to be used for alignment

1. With Selectionmethod active click in the
   alignment field

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Concept ModelingCross Section Alignment
Alignment using lines or axes.
Line chosen for alignment
Y
Edge Tangent
Axis chosen for alignment
Y
Edge Tangent
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Concept ModelingCross Section Alignment
Alignment using face normal.
Edge Tangent
Y
Alignment Faces
Y
Edge Tangent
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Concept ModelingCross Section Alignment
Alignment using sketch points. Note the order
of point selection determines cross section
alignment.
1
2D points
2
Y
Selected Line Body
Edge Tangent
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Concept ModelingCross Section Offset

• Cross Section Offset
• After assigning a cross section to a line body,
  the Detail property allows users to 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
• 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 ModelingCross Section Offset
Origin offset (no offset)
Line Body
Line Body with cross section displayed
Centroid/Shear Center offset
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Concept ModelingSurfaces From Lines

• Surfaces From Lines
• Creates surface body using line body edges as the
  boundary
• 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
• Planes, cylinders, tori, cones, spheres and
  simple twisted surfaces

• Details window
• Flip surface normals
• Input thickness which will be transferred to the
  FE model

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Concept ModelingSurfaces From Lines

• Notes on surface from lines
• A line body with no cross section can be used to
  tie together surface models. In this case the
  line body acts merely as a mechanism to insure a
  continuous mesh at the surface boundaries.

2 Surface Bodies
Result is continuous FE mesh at surface interface
Line Body (no cross section)
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Concept ModelingSurfaces From Sketches

• Surfaces From Sketches
• Creates surface bodies using sketches as
  boundaries (single or multiple sketches 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
• Can enter thickness which will be used in
  creating the FE model

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Concept ModelingSurfaces From Sketches . . .
2 ways to identify sketch for operation Click in
the Base Objects field
Select the desired sketch from the tree then
Apply
Select a portion of the desired sketch in the
graphics window then Apply
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Concept ModelingEdge Joints

• Edge Joints are the glue that holds together
  surface bodies that have been joined and concept
  models where beams and surfaces connect. Each
  time you create a Joint, Lines From Edges, or
  Surfaces From Lines feature, edge joints are
  implicitly created in DM

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Concept ModelingEdge Joints

• Edge Joints can be viewed by turning on the Edge
  Joints option in the View menu
• Edge joints are displayed in either blue or red.
• Blue edge joint is contained in properly defined
  multi-body part
• Red edge joint not grouped into the same part

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Workshop 6-1, Line and Surface Bodies

• Goals
• Create a sketch representing beams used to
  stiffen a panel.
• 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.
• gtFilegtNew, or Start Page
• Choose to create new geometry
• At the prompt, set the length unit to millimeter

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Workshop 6-1, Line and Surface Bodies

• Create a rectangle
• Sketch gt Rectangle
• Place the cursor near the origin until P
  appears, click then drag to define the rectangle
• Click gtLook At gtZoom to Fit tool buttons,
  and Triad ISO Ball as desired.

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Workshop 6-1, Line and Surface Bodies
Dimension the rectangle 600X300 mm as
shown Sketch gt Dimension gt General Horizontal
600 mm Vertical 300 mm Fit the sketch and move
dimensions as necessary Sketch gt Dimension gt
Move
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Workshop 6-1, Line and Surface Bodies

• Add 2 vertical lines and dimension as shown
• Sketch gt Draw gt Line
• Place the cursor near the top line until the C
  coincidence constraint appears. Move the cursor
  to the bottom line until the C appears and a
  V indicating a vertical constraint.
• Repeat for second line
• Apply horizontal dimensions as shown.
• Sketch gt Dimension gt Horizontal
• Adjust Details so all dimensions are as
  indicated

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Workshop 6-1, Line and Surface Bodies

• Create a Line Body from Sketch1
• Main Menu gt Concept gt Lines From Sketches
• Select Sketch1 from the Tree (click the
  near the XYPlane to expand that branch if
  necessary) and gtDetailsgtApply it as the base
  object
• Click gtGenerate

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Workshop 6-1, Line and Surface Bodies
Select a rectangular tube type cross
section Main Menu gt Concept gt Cross Section gt
Rectangular Tube After selection, the cross
section is displayed with its dimensions. In
this case we will use the default dimensions.
If desired the cross section Details can be
changed to modify the cross section.
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Workshop 6-1, Line and Surface Bodies

• With a cross section selected we now need to
  associate it with our line body.
• Highlight the line body in the tree and the
  details shows that no cross section is yet
  associated with it.
• tree gt 1 Part, 1 Body gt Line Body (at bottom
  of tree)
• Click in the Cross Section field
• Choose RecTube1 from the drop down list

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Workshop 6-1, Line and Surface Bodies
After assigning the cross section to the line
body the default display shows the line body with
its cross section alignment (see right). We can
also display the beam with the cross section
displayed as a solid. Main Menu gt View gt Show
Cross Sections Solids
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Workshop 6-1, Line and Surface Bodies

• The next step is to create the surfaces between
  the beams. These surfaces will be shell meshed in
  the FE simulation.
• Main Menu gt Concept gt Surfaces From Lines
• Hold the control key and select the 4 lines shown
  at right.
• (or can hold down LMB and sweep mouse over lines
  to be group selected)
• gtApply

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Workshop 6-1, Line and Surface Bodies
12. gtGenerate the Surface Body. Note a frozen
surface body is created, bounded by the selected
lines Repeat the previous steps to create two
more surface bodies gtGenerate as necessary
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Workshop 6-1, Line and Surface Bodies
The final modeling operation is to place all the
bodies into a single part (multi-body part).
We must do this to insure that, when meshed,
each boundary recognizes its neighbor resulting
in a continuous mesh. Set the Selection Filter
to Bodies. In the graphics window right
mouse click and choose gtSelect All
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Workshop 6-1, Line and Surface Bodies
With all bodies selected, again right click in
the graphics window and choose Form New
Part. By examining the Tree notice a single
part has been formed which contains 4 bodies.
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Workshop 6-1, Line and Surface Bodies

• Shown here we have moved to a Simulation
  environment in Workbench and meshed the
  geometry.
• By grouping all bodies into a common (single)
  part, nodal connectivity is insured.