Does anyone know if constraining two surfaces of a rotationally symmetric part to a fixed theta (with the cylindrical coordinate system Z-axis aligned with the axis of symmetry) is equivalent to a Cyclic Symmetry constraint? I have seen 90 degrees of a part constrained to fixed X on one side and fixed Y on the other side (Z is the rotation axis) as a recommended technique and was wondering if smaller included angles would work using a Cylindrical CSys. I do understand that the loads would have to be rotationally symmetric also in this technique, but I believe they would not if a Cyclic Symmetry constraint was applied.
Can anyone confirm or refure these suppositions?
Thanks very much for the help,
Alan Carlson Discern Engineering 1681 E. Hennepin Ave. Suite 180 Minneapolis, MN 55414-2562 (612)617-9258 (612)378-5503 FAX (612)270-3926 cell --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.677 / Virus Database: 439 - Release Date: 5/4/2004
Constraining the two cut sides of a "rotationally symmetric" body in theta is NOT the same as using a cyclic symmetry constraint .... unless the loads applied to the body are uniformly distributed about 360Ã‚Âº in a radial and/or axial manner. Any loads which are applied to the body in the "theta" direction (torque about "Z") require a cyclic symmetry constraint set, even if they are uniformly distributed, or "rotationally symmetric". This is because torques applied about the axial direction would produce circumferential deformations (theta direction). These deformations would not be permitted if a "theta" constraint is used in place of cyclic symmetry.
Regards,
Chris
Chris Kaswer Sr. Analytical Engineer The Timken Corporation Automotive - Needle Bearing Solutions 59 Field Street Torrington, CT 06790-1008 (860) 626-2426 - voice (860) 496-3638 - fax -
With cyclic symmetry you're looking at a pie slice. The two surfaces that you attach the cyclic symmetry constraints to must be the same shape and size (just rotated around the axis a bit) They do not have to be flat - they can be a wavy surface if you want.
Theses two surfaces are then coupled - so that any deflection that occurs at one is transferred to the other. So their stiffnesses effect each other.
By applying separate and independent constraints to two surfaces you won't get this coupled action, which is an important part of cyclic symmetry.
But it all really depends on what you're trying to achieve. It could be that independent cinstrainits are what you're after - they'll give more or a "mirror" effect rather than a "rotated" effect
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