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Point contact in a 3D structural mechanics model?
Posted May 5, 2011, 7:32 a.m. EDT Geometry, Modeling Tools & Definitions, Parameters, Variables, & Functions, Structural Mechanics Version 4.1 2 Replies
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I am trying to calculate eigenfrequencies of a part of a microscope. In this part a circular plate is hanging on three screws with ball-shaped ends. The screws contact the plate in V-shaped groves (see the attached file). Thus each screw makes two point contacts with grove walls. I define the surface of the screws and of the groves as identity pairs and then put a continuity condition in "Solid Mechanics". The eigenfrequencies I get by solving the problem seem to be reasonable. However, I am concerned about those point contact between the screws and the plate. I am wondering if I am doing something wrong with those point contacts and if I should redraw the model and make the contacts of finite dimensions to get a more correct solution?
In the future I am planning to do frequency dependent analysis of this geometry. I plan to put an excitation on the top of the cylinder and look at the displacement of the plate. Are the point contacts going to be a problem there?
regards,
Yuriy
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Capturing the actual contact area instead of point contact is always more accurate, however more complex to model. In your problem the contact area should always be small, so having point contact is fine as long as you don’t look at the high resulting stresses in the vicinity of the contact points. The eigenfrequencies and eigenmodes will not be affected that much, at least not for the lowest frequencies that you are considering.
That may change if you have no/very small friction. In that case, the displacement constraints resulting from frictionless point contact are different from those from the continuity condition that you now have and that may affect results.
If you need to get the actual contact area, it’s more accurate to do it with the same geometry that you have and use contact pairs (and some loading) instead of manually adjusting the geometry to increase the contact area.
Nagi Elabbasi
Veryst Engineering
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thank you for your advice! I will try to make preloaded contact pairs in my geometry and see how it affects the results.
Yuriy