MESH, CONNECT & SET UP MY

licoricehealthAI and Robotics

Nov 14, 2013 (3 years and 4 months ago)

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MESH, CONNECT & SET UP MY
MODEL FOR FEA STUDIES

by

D Duraikannu

Graphics Systems Corporation

MESH, CONNECT & SET UP

What is SolidWorks Simulation?


Design, Analysis Systems fully integrated within SolidWorks


SolidWorks Simulation provides one screen solution for several
types of analysis





Powered
by fast solvers, SolidWorks Simulation enables you to
solve large problems quickly using your personal computer.


SolidWorks
Simulation comes in several
bundles to
satisfy your
analysis needs.


SolidWorks Simulation shortens time to market by saving time
and effort in searching for the optimum.


Simulation Premium


Simulation Professional

2011 SolidWorks Simulation Product Bundles

Frequency/

Buckling

Thermal

SolidWorks
Premium

Static

SolidWorks

Motion

Drop Test

Fatigue

Nonlinear

Design Study,

Optimization

Pressure

Vessel

Composites

Advanced

Dynamics

Event Based

Motion

Flow

Simulation


Electronics


HVAC

Sustainability

Two Meshers: Standard Vs. Curvature

Standard Mesh

Curvature Based Mesh

Supports all possible

contacts/component
types

Default

mesher in
SolidWorks 2011

Activates
Veronoi
-
Delaunay scheme for
subsequent operations

Activates Curvature
-
based
meshing scheme for
subsequent operations

Creates uniform mesh all
around the

model

Creates more elements

in
higher
-
curvature areas
automatically curved


Uses “Global Size and

Tolerance”

啳敳

“Min/Max size,
number of elements,
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Meshing Stages


Evaluating Geometry


Geometry errors may cause failure


Processing boundary


Surface meshing


Creating mesh


Volume filling


Failure Diagnosis


Complex single body component causes problems


Improved a lot in 2011 SolidWorks

Preparing a Model for Analysis


Simplify geometry


Suppress cosmetic features


Be careful in selecting stress concentration areas


Check for rebuild errors


Assembles: Interferences


Often result of a poor modeling technique


Thickness Interferences in the case of shells, use
correct “Shell offset method”


new in 2011


Allowed only for Shrink fit

Example: Interference


Meshing problems due to interference are quite
common


Always check for interference in assembly


Tools
-
> Interference Detection


Interferences prevent compatible mesh


Re
-
mesh failed parts with incompatible mesh is
not always a good option

Importance of Good Quality mesh


Stress Concentrations


Application of mesh control is a manual process


Stress singularities: The more mesh is refined, higher
the stress valves


Adaptive Meshing


Available for Solids in Static Studies


Depends on loading types


Viewing Mesh and Results


Useful approach for checking behavior of the
model and mesh refinement level


Settings: Mesh boundary options


VON: Edit Definition
-
> Advanced Options
-
>
Element Valves


Stress is calculated at Gaussian points within
element


Element stress is an average of just the element


Nodal stress is an average of adjacent elements


Energy Norm Error


Shows % difference between element and nodal
stress for each element


Importance of Tolerance


For Standard Mesher: Tolerance is the valve below
which adjacent nodes will be merged


For Curvature based Mesher: In 2011, it is defined
based on Min/Max size, number elements around
holes and element ratio


Can be particularly importance for small features
being resolved


If global tolerance is 30% greater than the smallest
element size specified in mesh control, global
tolerance value is changed to 30% of smallest element
size

Tolerance and small features


Can be the cause of “Restraint transfer failed” or
“No loads applied” error when running a study


Has to do with mismatch between geometry used in
actual definition (faces/edges) and mesh generated


When getting restraint transfer failed error, check
defined restraint, and then “show mesh” to see if
area is resolved by mesh


Beware of the model that have small features
compared to overall dimensions

Example: Mesh Tolerance


Tolerance Too large: feature is not resolved







Tolerance made smaller (tighter) so nodes are not
merged

Mesh Type Selection in 2011


Treat as Beam


Treat as Solid / Beam


Can treat Solid Extrusion as beams
but must specify treat as beam


Define Shell By Selected Faces


At mid surface


At Top Surface


At Bottom Surface


Specify Ratio


Treat as Remote mass

Automatic Shell Realignment


Uses an algorithm to
attempt to line up shell
top and bottom surfaces
so they are consistent


Option to turn OFF / ON
is available through
“Simulation Options”
dialog


Note: Having option
enabled may cause
meshing to take longer
time if there are many
elements


possible to
flip shells manually

Detecting Bad Geometry


Use SolidWorks Utilities
Geometry Analysis tool


Requires SolidWorks Premium


Short edges, sliver faces,
etc

will
often cause mesh failure


Does not work on imported
geometry


Try exporting into IGES file and
importing into SolidWorks


Can often heals problems areas
(gaps / faces)

Compatible / Incompatible
M
esh


Affects solid/solid, solid/shell or shell/shell that are
touching


Compatible mesh with touching surfaces


‘Imprint’ of each face on the other


nodes line up at the
surface


Incompatible mesh with touching surfaces


Each component is mesh as if other is not there


“Improve accuracy for contacting surfaces with
incompatible mesh” option


mortar bonding

Contact / Gap Elements


No Penetration contact


Node to Node


Must touch initially


No sliding


forces applied
parallel to contact normal
force


Requires compatible mesh


Node to Surface


Each source node is assigned
a target element


Slower than node to node


Surface to Surface


Most general option


Most resource intensive


Supported for Nonlinear
studies

Contact Analysis tips


Direct Spare solver is preferred for
Contact problems


Set global contact to free to ensure
no undesired bonding occurs


contact hierarchy


Node to Surface is default option


Shell thickness is taken into account
for No penetration or virtual wall
contact


Bonding Diagnosis


Two possible error messages


Direct Sparse: “Model is unstable. Restraints may not
be adequate”


FFEPlus: “Iterative solver stopped”


Analysis fails


no results


Enable soft spring option


Large displacement flag may be thrown


Say “No” (do not rerun this large displacement option
on) and save the results and check the animation

Locating a node or element


Helpful for error messages referencing a
node/element


In Nonlinear Analysis check *.OUT file


Problems with convergence can have to do with specific
region and that can be due to meshing or contact
definition


Solver places a notes that reference specific
nodes/elements in *.OUT file


Right click on Mesh
-
> List selected


Node / Element location is annotated


Alternative approach: export as *.geo and search for node
number in notepad and get coordinates then insert a point

Beam Contact


Beam to beam contact is defined
by joints


No contact sets for beam to beam
contact


Can bond a beam joint or beam to
a shell / solid face


Beam joint or beam as set 1


Shell / solid face as set 2


Joints created at intersections of
neutral axes and free ends


Joint colors


Purple: joint connecting two or
more beams


Olive: free or disconnected joint

Additional contact analysis tips


If vertices and edges are involved in contacts, use
node to Surface


Mesh should be finer on set1 entity than on set 2


Can have convergence problems if set2 has finer mesh


Split lines reducing the source area can help speed up
the convergence


For nonlinear contact problems with nonlinear
material models, try draft quality


In linear static analysis, remember that only initial
and final positions are saved


animation may show
interference

Diagnostics using “Frequency Study”


Test for Rigid body motion (RBM)


FFEPlus with soft spring enabled


Combinations of restraints and
bonding with improper contacts
could result in RBM


Rigid body mode shows frequency
valves as closes to zero


Test for bonding behavior


Look at mode shapes animations


Loads can be suppressed for this
study


Copy study information from ‘static’
to ‘frequency’ or vice
-
versa

Thank You


For any questions/comments/feedbacks


dd@gxsc.com

&
joe.janik@gxsc.com


Phone: 1
-
800
-
454
-
2233


Many thanks to WIILSSUG Leader: Brain Kinnune
and Ruud Lighting, Inc.


See you all in Nov 2011
for next WI/IL
Simulation
User
group (WIILSSUG) meeting