Tie constraint - master/slave surface 1

[jball1]

When utilizing a tie constraint, the Abaqus help file says that the coarser mesh surface should be the master surface. I have also heard that the stiffer surface should be the master surface. What should be done when these two guidelines conflict? For example, I am running a model with a steel cylinder (fine mesh) surrounded by a foam material (coarse mesh). What surface should be the master surface at the interface of the steel and the foam?

Thank you,

Jake

 

[csk62]

The slave surface "goes" to the master surface, that is if you choose an adjustment option, the nodes on the slave surface are adjusted to meet the master surface. The slave surface is recommended to have higher mesh density. For tie constraints, I would be very careful. Sometimes if you select the surface-surface tie, nodes lie outside the analysis computed default distance, and some nodes do not end up being tied as you might think.

 

[IceBreakerSours]

If the materials are of the same stiffness, a coarser mesh will act "stiffer". Think of the "flexibility" that the mesh has (when compared with a finer one) in terms of degrees of freedom (or, more appropriately, displacement field). I like to imagine a carpet (i.e., mesh) in 3D Euclidean space that can be bent in to various shapes; the more nodes it has (finer mesh), the more variations the carpet can have, the more "flexible" it is. Conversely, the fewer nodes it has (coarser mesh), the "stiffer" it is.

Are you new to this forum? If so, please read these FAQ:

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[rstupplebeen]

When the guidelines are conflicting often I'll run it both ways. If the results are similar I go with the one that solved faster. I hope this helps.

Rob Stupplebeen

http://www.optimaldevice.com

https://sites.google.com/site/robertkstupplebeen/

 

[jball1]

Thanks all for the help. It looks like there are several different ways to think this through.

Yes, Icebreakersours, I am new. Thanks for the FAQs links. I suppose I should introduce myself:

I have worked for the last two years as a mechanical design engineer, and then recently took a job doing finite element analysis. I have always wanted to do analysis, and so I am pretty excited about the opportunity, but I am very inexperienced (other than the standard cantilever beam, load in the center of a plate fixed on all sides, etc, simple type problems in school). Looking forward to being a part of this community. Thanks again.