meshing and fe model creation - stress analysis experts · pdf filemark sherman, director -...
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Unrestricted © Siemens AG 2013 All rights reserved.
Mark Sherman, Director - FEMAP Product Development
Meshing and FE Model Creation
Unrestricted © Siemens AG 2013 All rights reserved.
Page 2 Siemens PLM Software
Who am I?
What you will learn
Femap capabilities
Demonstrations
Benefits of this topic
How to learn more
Agenda
<Presentation title>
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0D – Meshing
Mass Elements
1. Create Mass Property manually
and attach to nodes
2. Use Tools, Mass Properties,
Solid Properties
- Select Solid
- Answer “Yes” to “Ok to create a
representative node and mass
element”
- Enter Mass Density
Meshing in FEMAP 0D
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1D – Meshing
FEMAP “Line Elements”
Manual Creation
Pick two Nodes – Defines X Axis
Node or Vector for Cross-Section
Alignment – Defines Y and Z Axes
Reference Point or Vector Offsets to
define relation of Cross Section to
selected Nodes
Meshing in FEMAP 1D
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Still around since the DOS version of
FEMAP – Mesh, Between does
exactly that, lays down elements
between two user select points
Based on the Coordinate System
selected, rectilinearly, cylindrically, or
spherically
Meshing in FEMAP 1D – Mesh Between
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Reference Point is the most powerful
and useful feature when meshing
with 1-D elements in FEMAP
Controls where automatic element
offsets will be created to align the
Reference Point with the element’s
nodes, or with the geometric curve
used to mesh on
Meshing in FEMAP – 1D
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Mesh, Mesh Control, Attributes On
Curve
• Pre-Assign Property, Orientation,
and Offsett, including using the
Reference Point offset
Meshing in FEMAP – 1D – On Geometry
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This automatic handling of beam offsets and orientations saves you
a lot of time in bookkeeping – NASTRAN expects the nodes to be at
the Shear Center of the Beam, but the nodes are where the nodes
are, FEMAP automatically sets up the offset from the nodes to the
Shear Center on the CBEAM card, and the offset from the Shear
Center to the Neutral Axis on the PBEAM card
Meshing in FEMAP – 1D – Reference Point
$ Femap with NX Nastran Property 3 : BEAM Property (Angle (L) Section)
$ Femap with NX Nastran PropShape 3 : 11,0,0.5,0.5,0.,0.,0.05,0.05
$ Femap with NX Nastran PropOrient 3 : 11,0,1.,1.,2.,5.,6.,1.,-0.0265092,0.0265092
PBEAM 3 1 .0475 .001125 .0011256.6612-4 3.898-5 0.+
+ -.026509.0265092-.026509-.473491 .473491-.023491 .473491.0265092+
+ YESA 1. +
+ .4313074.4313074 +
+ .116912-.116912 .116912-.116912
$ Femap with NX Nastran Material 1 : 7050-T651 Al Plate .25-.5
MAT1 1 1.03+7 .332.6424-4 1.28-5 70. +
+ 66000. 65000. 44000.
MAT4 1.0020602 88.8722.6424-4
GRID 16599 011.51183 -9.737 7.7875 0
GRID 26984 011.52945-9.64448 7.7875 0
CBEAM 14815 3 16599 26984 0. 0. 1. +
+ -.026041.0049599.0265092-.026041.0049599.0265092
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Modify, Update Elements
Update –
• Orientation
• Offsets
• Reverse
Meshing in FEMAP – 1D - Updates
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API – Custom Updates
Since a Vector only points in one
direction, all elements created at the
same time are aligned with that
Vector.
FEMAP ships with an API that can
update beam orientations to align
normal with a selected surface.
Meshing in FEMAP – 1D - Updates
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Meshing in FEMAP – 1D - Connections
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Mesh Closest Link finds the closest
node for each node in the first
selection.
If the first selection has more nodes
that the second, you will get multiple
elements at some of the nodes.
Mesh, Connect, Multiple collects the
same setup information, and let’s the
user pick the two nodes for
connection
Meshing in FEMAP – 1D - Connections
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Unzip disconnects a Shell Mesh
leaving coincident nodes.
In relation to 1-D Meshing, can also
automatically create a 1-D
connection between the original
nodes and the new nodes
Coincident Link uses FEMAP
Coincident Node checking
functionality and instead of merging
the nodes, can automatically create
1-D connection
Meshing in FEMAP – 1D – Unzip & Coincident Link
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Mesh, Edge Members
Meshes the Free Edges of a Shell
Mesh with any 1-D Line Element
Select the Shell Elements to use
Pick nodes to define which free
edges of the shells get the 1-D Line
elements
Later on we’ll see how this same
command can create shell elements
on the free faces of a solid mesh
Meshing in FEMAP – 1D – Edge Members
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Still around since the DOS version of
FEMAP – Mesh, Between does
exactly that, lays down 2-D elements
between 3 or 4 user selected points
Based on the Coordinate System
selected, rectilinearly, cylindrically, or
spherically
Meshing in FEMAP 2D– Mesh Between
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Mapped Meshing Options
• When possible, FEMAP will lay
down a “mapped” m x n mesh, the
meshing algorithm will try to find
four corners and mesh a
parametrically re
Meshing in FEMAP – 2D – Quadrilateral
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When “Mapped Meshing” is turned
on, FEMAP will also use hard-coded
transition meshes between fully
mapped areas.
Meshing in FEMAP – 2D – Mapped Meshing
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Quad Edge Layers – attempts to lay
down perfect layers of quads on the
periphery of a quad mesh, when
things get too twisted, it stops. The
remainder of the mesh is then free-
meshed.
Meshing in FEMAP – 2D – Options
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Post-Mesh Cleanup – Looks for
certain skewed and undesirable
mesh patterns and replaces with
better shaped elements – have not
see a case where it’s not best to
have this option on
Meshing in FEMAP – 2D – Options
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“Min Elements Between Boundaries”
forces the number of nodes entered
between any cuts made by FEMAP’s
boundary mesher
Meshing in FEMAP – 2D - Options
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“Cut Quads with Angle Deviation
Above” – enter the maximum angle
acceptable in a transition quad
before FEMAP automatically splits it
into two triangles. The higher the
angle the less triangles in a mesh
Meshing in FEMAP – 2D - Options
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Three triangle meshers in FEMAP.
“Auto” – tells FEMAP to use the best
one
3-D surfaces it will use the 3-D Tri
Planar Surfaces use Fast Tri
Subdivision is the oldest Tri-Mesher
and is used if any of the others fail
Meshing in FEMAP – 2D – Triangle Meshing
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Available in Quad Meshing, but more
appropriate to triangle meshing –
“Growth Factor” during sizing…
Very useful when optimizing total
model size for large tetra meshes
Meshing in FEMAP – 2D – Triangle Meshing
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All Tetrahedal Meshing in FEMAP
starts with a triangular surface mesh
• Triangles are fed into the INRIA
tetrahedral mesher (used by most
FEA vendors)
• Returned Tetrahedron exactly
match the faces of the original
triangles
Meshing in FEMAP – 3D - Tetrahedral
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Tetra Mesher handles internal
triangles or quads, and creates a
combined shell / solid mesh with
slight embed for moment transfer.
Meshing in FEMAP – 3D - Tetrahedral
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Internal and branching faces and
curves are accounted for within a
solid
• Create a consistent mesh in
volumes containing 3D, 2D, and 1D
entities
Example:
Reinforced concrete model: steel
beam elements with concrete tetra
elements in a matched mesh
Meshing in FEMAP – 3D - Tetrahedral
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Hexahedral Meshing
Subdivide and Hex mesh
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Mesh – Copy, Rotate, Reflect
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Mesh – Extrude, Revolve Sweep
Curves to Plates
Line Elements to Plate Elements
Plate Elements to Solid
Elements
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Automatic Solid Geometry Preparation
Geometry and Meshing Considerations
Problematic geometry
• Analysts inherit CAD models that often contain difficult geometry
• Serviceable for CAD, but cause problems with FE meshing
• Affects mesh and element quality and hence solution accuracy
• Typical problems include:
• Sliver surfaces
• Short edges
• Narrow regions
• Close points
• Internal voids
• Difficult geometry has to be fixed before
the model can be meshed
• Manual geometry clean up requires
much effort and time
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Automatic Solid Geometry Preparation
Geometry and Meshing Considerations
Too much geometry detail
• CAD models often contain too much modeling detail for FEA
• Small features that are not required for analysis
• Must be removed before meshing
The solution:
• Femap’s automatic geometry
preparation capability
• Greatly reduces and in many
cases completely eliminates the
need for manual combination,
suppression and splitting of
geometry
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Automatic Solid Geometry Preparation
• Automatic clean up allows:
• Easier meshing of complex 3D
models with problematic
geometry
• Easy removal of unnecessary
detail
• Geometry preparation actions
performed automatically include:
• Combination of surfaces and
curves
• Suppression of small curves and surfaces
• Surface splitting at strategic locations
• User defined tolerance controls extent of
geometry changes
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Automatic Solid Geometry Preparation
• Prepare Geometry and Mesh sizing tolerances
• Guide geometry feature removal / suppression and mesh
sizing
• Internal voids identified and removed
• Access to further geometry preparation and mesh sizing options
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Automatic Solid Geometry Preparation
• Full control over the extent of model simplification
• Identify a group of entities that should be ignored
• Entities that are loaded or constrained are ignored
• Set maximum sizes and angles based on geometry preparation
tolerance
• Identify individual operations to be included in the cleanup
process
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Page 35 Siemens PLM Software
Meshing in FEMAP
The Meshing Toolbox – Live Discussion/Demonstration