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"End caps" on a beam
Posted 27.07.2010, 18:04 GMT-4 1 Reply
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I am a fairly new user and have what I think should be a simple problem, but cannot figure it out. I want to make sure I don't have any fundamental misconceptions here.
I just want to do simple analysis of a fixed-free cantilever beam with a "plus" (i.e. "+") shaped cross section, loaded at one end. However, I want to place an "end cap" on the beam so that the free end is still free to rotate or translate as a whole but must maintain its original "+" shape. I figured out how to do this in "Structural Mechanics -> Solid Mechanics (solid)" by adding a "Rigid Connector" to the end of the beam. This works fine to fix the shape since rigid connectors are still allowed to translate or rotate. Intuitively it seems like it would make more sense and be less computationally expensive to use the "Stuctural Mechanics -> Beam" model. However, the "Rigid connector" option does not appear to be available in the "Beam" physics setting, so I cannot figure out how to constrain the shape of the end of the beam.
I am also not totally clear how to apply boundary conditions or loads to the end of a beam, since the beam mode only lets you select edges or points, and not faces. If I want one end of the beam to be fixed, do I need to apply a "fixed" boundary condition to every point and edge on that end (as opposed to just fixing the surface which you would do in a 3D model)? Also, selectable points only appear at the outer corners of the "+" shape, so I cannot figure out how to apply a load in the center. I tried creating an extra point in the center of the end of the beam, but then cannot apply a load to that point.
Finally (I believe there might be other threads on this topic but I haven't done an extensive search yet), the beam geometry is very thin. The length is 10mm, width of the "+" is 5mm but thickness is only 25 microns, so I have to use a very coarse mesh to avoid running out of memory. Are there any more customizable mesh settings or element types designed for use with very thin features?
To summarize, I'm looking for answers to three questions:
1) How to place a rigid end cap on a beam using the "Beam" physics model
2) How to load a point on a beam that is not already defined automatically by the beam geometry
3) Recommendations for meshing thin features
I just want to do simple analysis of a fixed-free cantilever beam with a "plus" (i.e. "+") shaped cross section, loaded at one end. However, I want to place an "end cap" on the beam so that the free end is still free to rotate or translate as a whole but must maintain its original "+" shape. I figured out how to do this in "Structural Mechanics -> Solid Mechanics (solid)" by adding a "Rigid Connector" to the end of the beam. This works fine to fix the shape since rigid connectors are still allowed to translate or rotate. Intuitively it seems like it would make more sense and be less computationally expensive to use the "Stuctural Mechanics -> Beam" model. However, the "Rigid connector" option does not appear to be available in the "Beam" physics setting, so I cannot figure out how to constrain the shape of the end of the beam.
I am also not totally clear how to apply boundary conditions or loads to the end of a beam, since the beam mode only lets you select edges or points, and not faces. If I want one end of the beam to be fixed, do I need to apply a "fixed" boundary condition to every point and edge on that end (as opposed to just fixing the surface which you would do in a 3D model)? Also, selectable points only appear at the outer corners of the "+" shape, so I cannot figure out how to apply a load in the center. I tried creating an extra point in the center of the end of the beam, but then cannot apply a load to that point.
Finally (I believe there might be other threads on this topic but I haven't done an extensive search yet), the beam geometry is very thin. The length is 10mm, width of the "+" is 5mm but thickness is only 25 microns, so I have to use a very coarse mesh to avoid running out of memory. Are there any more customizable mesh settings or element types designed for use with very thin features?
To summarize, I'm looking for answers to three questions:
1) How to place a rigid end cap on a beam using the "Beam" physics model
2) How to load a point on a beam that is not already defined automatically by the beam geometry
3) Recommendations for meshing thin features
1 Reply Last Post 28.07.2010, 04:13 GMT-4
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Posted:
1 decade ago
Hi
if you have an end cap it probably also has some mass, hence influences the eigenfrequencies no ? Do not forget to add it accordingly (slightly tricky in 3D)
You have another example in the 3.5 doc about how to rigidify an edge of a 3D beam, that could, I believe also be adapted and used
--
Good luck
Ivar
if you have an end cap it probably also has some mass, hence influences the eigenfrequencies no ? Do not forget to add it accordingly (slightly tricky in 3D)
You have another example in the 3.5 doc about how to rigidify an edge of a 3D beam, that could, I believe also be adapted and used
--
Good luck
Ivar