adams contacts [compatibiliteitsmodus] - in summa€¦ · 1 adams methodology contact modeling...
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ADAMS Methodology
Contact Modeling(Webex Walter Daniel, MSC.Software)
Benelux ADAMS User Meeting
Chris Verheul, SayField International
ADAMS Methodology
Contact Modeling(Webex Walter Daniel, MSC.Software)
Benelux ADAMS User Meeting
Chris Verheul, SayField International
ADAMS Contacts Topics
•Overview
•Theory and Parameters
•Geometry and Contacts
•Contacts Outputs
•Best Practices and Tips
•Contact Examples
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Contacts Overview
� Objectives:� Show the source and development of ADAMS
contacts
� Deeper understanding of ADAMS contacts
capabilities and settings
� IMPACT function description
� Analytical & ADAMS geometry vs. 3D
CAD geometry
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IMPACT Function
� Has been in ADAMS/Solver for many years
� IMPACT(dist, veloc, d_trig, k, e, c, d)
� Stiffening spring (e >1.0) that limits penetration
� User includes distance, velocity and trigger distance
� Basis for later contact development
� Still useful today
� BISTOP: for two sided contact
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General Solid Geometry Contact
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Robust and Accurate Polygon Interference Detection
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Contacts Theory and Parameters
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Contact Friction parameters
� Contacts: Velocity only based friction step-step function)
� Joints: Stick-slip friction law with max deforma-tion (brush model type)
� Note: low Vstiction � stiff damper
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Contacts and Geometry
� ADAMS analytical shapes
� ADAMS CSG solids
� Imported CAD solids
� Imported CAD shells
� Converted ADAMS geometries
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ADAMS CSG solids
� Full parametrisation is maintained !!
� Loss of analytical functionality � tricking
is OK� Set part inertia to
User Defined
� Add fake geometry
for contacts
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Converted ADAMS geometries
� Use RAPID + ADAMS/Solver to Export *.shl file from any geometry
� Advantages:
� Freeze accuracy of mesh used by
RAPID
� Visualise RAPID contacts mesh
� Speed up Solver start for multiple
runs
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Analytical Geometry + RAPID
� Since ADAMS 2010: more use of analytical geometry in contact with 3D solids
� Analytical solids are automatically detected
� Only pure sphere / cylinder / torus / box frustum allowed (no CSGs)
� Vast improvement of speed and accuracy
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Contact Outputs
� Pre-defined object measures for
Last_Run
� Function Measures
� Contact Tracks
� User Routines: cffsub + cnfsub
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Contact User Routines
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� CNFSub: Contact Normal
Force Sub.
� CFFSub: Contact Friction
Force Sub.
� Modification of Normal Force
& Contact Friction laws
� Additional Contact Data
Output: Pen, Vel, …
Best Practices and Tips
� Integrator & contact settings
� Geometry penetration
� Contact patch size
� Static equilibrium
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Integrator & contact settings
� Default GSTIFF integrator works
well
� Using Hmax may help
� Change to SI2 Formulation better
handles
speed changes
� Many contacts: consider HHT
integrator
� Test & tweak Mesh tolerance
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� Challenges in contact penetration
� Extremely thin objects in contact
� � additional contact geometry
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Static Equilibrium with Contacts
� Static Eq. can work with contacts
� Defaults parameters usually not OK
� Use small TLimit (transl. limit per
iteration)
� Likely increase Maxit (Max. iterations)
� Move parts to start with engaged
contacts !!
� Remember: speed based friction
only (i.e. on slopes)
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Example: Friction tester
� Solid geometry � analytical contact
� Plane – Sphere - Plane
� Completely contact balanced part: SI2 faster
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Example: Friction tester
Example: Magic Spin
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