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[ABAQUS] Convergence problems

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kamcio326

Mechanical
Jan 17, 2016
4
Hi!

Currently i'm performing bracket analysis, which is connected to ring with bolt joints. In 1st step of analysis I' am applying bolts preload and at the 2nd concentrated force to bracket via coupling constraint.
I noticed that this steps separately (2nd step with coupling constraints in place of bolts) resolve correctly but if i submit them both Abaqus has convergence problems during resolving second step. I've tried automatic stabilization, contact controls and nothing helps.

Please help

Warnings:

Whenever a translation (rotation) dof at a node is constrained by a kinematic coupling definition the translation (rotation) dofs for that node cannot be included in any other constraint including mpcs, rigid bodies, etc.
THE SLAVE SURFACES ASSEMBLY_CP-139-BRACKET-1 AND ASSEMBLY_CP-140-BRACKET-1 INTERSECT EACH OTHER. THEY ARE PAIRED WITH MASTER SURFACES ASSEMBLY_CP-1-RING-1 AND ASSEMBLY_CP-2-RING-1 THAT ALSO INTERSECT EACH OTHER. IF BOTH PAIRS ARE *CONTACT PAIRs, THESE TWO PAIRS SHOULD NOT BE SIMULTANEOUSLY PRESENT IN A STEP BECAUSE OF POSSIBLE CONVERGENCE PROBLEMS; USE *MODEL CHANGE,TYPE=CONTACT PAIR TO REMOVE ONE OF THEM. IF BOTH ARE *TIE PAIRS, THE REDUNDANT TIES WILL BE REMOVED AUTOMATICALLY. IF ONE PAIR IS *TIE AND ANOTHER IS *CONTACT PAIR, REMOVE ONE OF THEM.

MPCS (EXTERNAL or INTERNAL, including those generated from rigid body definitions), KINEMATIC COUPLINGS, AND/OR EQUATIONS WILL ACTIVATE ADDITIONAL DEGREES OF FREEDOM

5193 elements are distorted. Either the isoparametric angles are out of the suggested limits or the triangular or tetrahedral quality measure is bad. The elements have been identified in element set WarnElemDistorted.

Excessive distortion at a total of 252 integration points in solid (continuum) elements

Excessive distortion at a total of 18 integration points in solid (continuum) elements
 
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Your printout is not showing the reason for the nonconvergence. It just warns that some couplings might overlap with each other or other definitions, that two slave surfaces overlap and interact with the master surface, some elements are bad, ...

Look into the .msg file for the actual reason of the nonconvergence.
 
Hi,

Not sure I got the idea with the two steps. Each one of them is running separately? or just one of them?

Anyway, try to eliminate the convergence error by removing interactions or constraints.
It seems that there might be an issue with the initial contact at the beginning of the step. Try to use 'interference fit'.

T.
 
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