“Excessive rotation of node” and "restart"

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“Excessive rotation of node” and "restart"

Huichao Liu
Hi guys,
How to use "restart" to bypass "Excessive rotation of node"?
I'm performing quasi-static tensional crack using Abaqus/explicit. After one-day calculation, an error, "Excessive rotation of node" occured.
And I found that the only two nodes with excessive rotation located at a fragment which had already broken free from the main structure.
So, it won't affect anything if abaqus can ignore the whole fragment and restart the analysis, bypassing the "Excessive rotation of node" problem.
Is there anyway to achieve such goal?


Best regards,
Charles
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Re: “Excessive rotation of node” and "restart"

Huichao Liu
Hi again,
Here are two methods I have tried.

 1. Fix the two nodes of excessive rotation.
 
  First, creat a node set after read restart data,
 

 *Nset, nset=Assembly.GN600-1.set-deleteel
 5422,5423
 

 Then, specify a boundary condition within the restart step to fix the motion of the two nodes:
 

 **fixed the two nodes
 *boundary
 Assembly.GN600-1.set-deleteel, 1, 1
 Assembly.GN600-1.set-deleteel, 2, 2
 Assembly.GN600-1.set-deleteel, 4, 4
 Assembly.GN600-1.set-deleteel, 5, 5
 Assembly.GN600-1.set-deleteel, 6, 6
 

 

 2. Using viscous pressure to drag down the motion of the two nodes
 

 First, creat a set of surfaces based on related elements after read restart data,
 

 *Surface, type=ELEMENT, name=Assembly.GN600-1.Surf-19-fragments
 1685, 1686, 1938, SPOS
 

 Then, specify a viscous pressure on the surface set within the restart step,
 


 *Dsload
 Assembly.GN600-1.Surf-19-fragments, VP, 1.063e-05

 

 

 However, neither of the measures worked. Calculation aborted with the same  "Excessive rotation of node" error at the same step time.
 I have ploted and compared the displacements of the two nodes. It seems the specified boundary condition or viscous pressure have no effect on the motion of them.
 

 Could anybody shed some light on this?
 

 Best,
 Charles
 

 ===================
 

 This is the error message and one of my restart inp file.
 

 Error massage,
 

 ***ERROR: Excessive rotation of node number GN600-1.5422
 ***ERROR: Excessive rotation of node number GN600-1.5423
 ***ERROR: Excessive rotation of node number GN600-1.5422
 ***ERROR: Excessive rotation of node number GN600-1.5423
 

 ***ERROR: Excessive rotation increments at 4 nodes

 

 Restart inp file,
 

 *Heading
 ** Job name: Layered_SE12_01rho_00cmp_02e Model name: Voroitria-partlyRefined-rigid
 ** Generated by: Abaqus/CAE 2018
 *Preprint, echo=NO, model=NO, history=NO, contact=NO
 *restart, read, step=2
 

 *Surface, type=ELEMENT, name=Assembly.GN600-1.Surf-19-fragments
 1685, 1686, 1938, SPOS
 ** ----------------------------------------------------------------
 **
 ** STEP: Step-3
 **
 *Step, name=Step-3, nlgeom=YES
 *Dynamic, Explicit
 , 0.8
 *Bulk Viscosity
 0.4, 1.2
 **
 ** BOUNDARY CONDITIONS
 **
 ** Name: BC-7-rightrp Type: Displacement/Rotation
 *Boundary, amplitude=Amp-Smooth2
 rigidity-2.Set-1-rp, 1, 1, 0.24001
 **
 ** LOADS
 **
 ** Name: Load-2-drag-fragments   Type: Pressure
 *Dsload
 Assembly.GN600-1.Surf-19-fragments, VP, 1.063e-05
 **
 ** OUTPUT REQUESTS
 **
 *Restart, write, number interval=1, time marks=NO
 **
 ** FIELD OUTPUT: F-Output-1
 **
 *Output, field, number interval=1000
 *Node Output
 A, RF, U, V
 *Element Output, directions=YES
 E, EDT, EMSF, LE, PE, PEEQ, PEEQVAVG, PEVAVG, S, STATUS, SVAVG
 *Contact Output
 CSTRESS,
 **
 ** HISTORY OUTPUT: H-Output-1
 **
 *Output, history, time interval=0.0008
 *Energy Output
 ALLAE, ALLCD, ALLCW, ALLDMD, ALLFD, ALLIE, ALLKE, ALLMW, ALLPD, ALLSE, ALLVD, ALLWK, ETOTAL
 *Incrementation Output
 DMASS,
 *End Step