Merge geometry or tie constraint 3

[frztrb]

Hello,
What type of modelling in Abaqus do you prefer?
I mean when it is recommended to merge geometry from parts into single large part?
How often do you use tie constraint?
As far I know the effect is almost the same - we can tie together parts of the geometry - we can tie together degrees of freedom at nodes.

What is influence of using tie constraint/merging mesh on results of the analysis?
Let's assume, that in both cases the finite element mesh is the same.

Thanks.

 

[IceBreakerSours]

Assuming the same mesh in the two cases:

From a numerical point of view, with *TIE, you are still left with additional equations in the stiffness matrix because you have more nodes, whose slave DOFs will be eliminated from the computations before handing over the matrix equation to the solver.

From a practical standpoint:

a) In a small model, difference will not be apparent. However, in a computationally expensive analysis, number of nodes/nodal DOFs matters.
b) If the displacement solution is varying smoothly over the computational domain, then again, no difference will be seen. If the displacement solution does NOT vary smoothly or has a sharp transition, *TIE will show a discontinuity/sharper transition.

Kinematic constraints (such as *TIE) are to be used in situations where the meshes simply can not be matched at the interface. Same mesh or not, it is preferable to reduce the number of nodes and ensure displacement continuity, if you can - this is one of those areas where the 'art' lies. More generally, too, one must strive for a 'simple' model (while capturing all the phenomena of interest as best as possible and ensuring low computational cost - particularly during the method development stage.)

Good question.

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