from cad to fea through functional annotations
DESCRIPTION
Ahmad Shahwan Jean-Claude Léon Gilles Foucault ROMMA status briefing December 2012. From CAD to FEA through functional annotations. Overview. Workflow Reminder From Global Coordinate Systems to Local Coordinate Systems Limitations of Global CS Adopting Local CS - PowerPoint PPT PresentationTRANSCRIPT
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Centre National de la Recherche Scientifique Institut National Polytechnique de Grenoble Université Joseph Fourier
Laboratoire G-SCOP46, av Félix Viallet38031 Grenoble Cedexwww.g-scop.inpg.fr
From CAD to FEA through functional annotations
Ahmad Shahwan
Jean-Claude Léon
Gilles Foucault
ROMMA status briefingDecember 2012
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Overview
• Workflow Reminder• From Global Coordinate Systems to Local
Coordinate Systems• Limitations of Global CS• Adopting Local CS• Screw Addition/Subtraction• Local CS and Internal Forces Cycles
• Indeterminate Static Equilibrium• New Results
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Workflow Reminder
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Limitation of Global CS
OBz
,/1
1
1
0
0
0
OB
y
x
,'/1
1_1
11
0
OB
y
x
,/2
22
22
0
OBz
y
x
,'/22
22
22
(3.5 DoF) (2 DoF)
(1 DoF) (0 DoF)
Interface CS Global CS
OBz
y
x
,/
OBz
y
x
,'/
+ +
= =
• Studying the nut equilibrium:
• Using Global CS
Spline connection is valid!
• Using Interface CS
Spline connection is invalid.
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Choosing Local CS
• To enable summation of screws:
• CS should be unified over components interfaces.
• CS for each component;
• Chosen amongst those of its interfaces.
Two interfaces with the same CSTwo interfaces with different CS’s
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Adopting Local CS• Previously, mech. screws were expressed according to one
global CS.
• Now, screws are associated with there own CS.
• For static equilibrium analysis, same principals hold.
• need to unify B.
•
{ �⃗�|⃗𝑀 }/ B 0+ {�⃗� 2|⃗𝑀 2 }/ B 2+ {�⃗� 3|⃗𝑀 3 }/ B3{ �⃗�|⃗𝑀 }/ B 0+ {⃗𝐹 ′ 2|⃗𝑀 ′ 2 }/ B0{ �⃗�|⃗𝑀 }/ B 0+ {�⃗� 3|⃗𝑀 3 }/ B 3{ �⃗�|⃗𝑀 }/ B 0+ {⃗𝐹 ′ 3|⃗𝑀 ′ 3 }/ B 0{ �⃗�|⃗𝑀 }/ B 0
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Screw Addition/Subtraction
Summation Step Used in GCS
Used in LCS
Output
Start
Calculate rotation matrix No Yes
Apply rotation matrix No Yes
Update moments Yes Yes
Sum vectors
Yes Yes
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LCS & Internal Force Cycles
1
2
34
5
z
y
x
z
• Originally internal forces where projected on each
axis of the GCS Graph of force propagation.
• This is not possible any more!
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LCS & Internal Force Cycles
1
2
34
5
• Generate force propagation graph independently from CS.
• Currently, we only propagate forces between contacts and threads;
• Advantage: force propagates in one direction through theses interfaces.
• Disadvantages: not general enough!
• Detecting propagation direction at threaded links.
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LCS & Internal Force Cycles
• Example of cylindrical washer elements.
• Here internal forces propagate through
shaft/bushing link.
• Problem with this kind of interfaces is that
they defuse internal forces in more than one
direction!
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Indeterminate static equilibrium
• Indeterminate static (hyperstatic) equilibrium may be
functional, or may indicate anomaly.
• Nut/counter-nut tightening is an
example of functional hypestatic
configurations.
• Indeterminism is used here to increase
internal system energy.
𝐹 1𝑧−𝐹2 𝑧−𝐹 3𝑧=0
• Incorrect interpretation of tight fit
produces an erroneous hyperstatic
equilibrium.
• This may helps the elimination of
irrelevant interpretations.
𝐹 1𝑧−𝐹2 𝑧−𝐹 3𝑧=0
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Indeterminate static equilibrium
3
2
1
1
32
Isostatic Hyperstaticas a result of detection error
Hyperstaticfunctional
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New Results
• Manipulating the way
facts are submitted.
• Adding new rules.
Recognition of new
components
• Distinction between nuts
and counter-nuts in the
root
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Thanks