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Alice

Node deactivated from interface

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Hello,

 

I use Radioss for a dynamic impact problem, but also for the moment to validate my model through a quasi-static analysis.

 

A first component compresses a second component with an imposed velocity. The interface between them is of type 7. In dynamic explicit simulation the interface works fine but in the implicit simulation, I get a warning in interface : "NODE ... DE-ACTIVATED FROM INTERFACE". If I make an "initial penetration" (initial gap < gapmin entered into type 7 interface) I do not get this problem (however I get initial constraints I want to avoid).

 

Would anyone know what the problem might be ?

 

Hereunder a part of my engine.out file:

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

 CYCLE    TIME      TIME-STEP  ELEMENT          ERROR  I-ENERGY    K-ENERGY T  K-ENERGY R  EXT-WORK MAS.ERR
     0   0.000      0.2000E+05 SOLID      39426   0.0%   0.000       0.000       0.000       0.000       0.000    
     ANIMATION FILE: pression_statique_07A001 WRITTEN
  ***** WARNING : ELEMENT FORMULATION ISOLID=    0
     IS NOT AVAILABLE FOR STIFFNESS MATRIX BUILDING, USING GENERIC ONE INSTEAD
      POSSIBLE CONVERGING ISSUE. *****
 
   *--------- STIFFNESS MATRIX SETUP ---------*
 SYMBOLIC DIM : ND =  155532 NZ =   2897175 NB_MAX =      26
 FINAL    DIM : ND =   47480 NZ =    761383 NB_MAX =      26
 
     --STIFFNESS MATRIX WILL BE REFORMED AFTER EACH    3  ITERATIONS--
 
 
   * CONVERGED WITH    0 ITERATIONS, |du|/|u|,|r|/|r0|,|dE|/|E|= 0.1000E+01 0.0000E+00 0.1000E+01
 
 WARNING INTERFACE        701
 NODE      13703 DE-ACTIVATED FROM INTERFACE
 WARNING INTERFACE        701
 NODE      13548 DE-ACTIVATED FROM INTERFACE
 WARNING INTERFACE        701
 NODE      13693 DE-ACTIVATED FROM INTERFACE
     ANIMATION FILE: pression_statique_07A002 WRITTEN
 
   * IMPLICIT COMPUTATION TERMINATED WITH    TOTAL NONLINEAR ITERATIONS:       0
   * TOTAL NUM.OF MATRIX FACTORIZATION AND PCG ITERATION:      0         0

     RESTART FILES: pression_statique_07_0001_[0001-0001].rst WRITTEN
     -------------

 
                           ** CPU USER TIME **
 
 #PROC  [K]SETUP [M]SETUP IMPL.SOLV IMPL.TOTAL
   1   .4862E+02 .0000E+00 .0000E+00 .4930E+02
 #PROC  CONT.SORT  CONT. F   ELEMENT  KIN.COND.  INTEGR.    I/O     TASK0     ASSEMB.   RESOL  
   1   .5591E-01 .6813E-02 .2678E+00 .2133E-01 .4654E-03 .5012E+00 .9117E-03 .1199E-01 .5030E+02

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

 

Thank you a lot,

 

Kinds regards,

 

Alice

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Guest

Hi Alice,

As a workaround, can you set the Irem_gap as 1 in interface parameters and run the analysis. Please update

 

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Hello George,

Thanks for your quick reply. I did not see it right away.

 

I solved my problem of slave nodes deactivation by initiating the implicit time step (/IMPL/DTINI). I tried setting Irem_gap to 1 but it did not change the fact that the interface is not taken into account.

 

Now, there isn't even an error. No slave node is deactivated but the animation shows a penetration. I constantly change the parameters in the interface as well as in the engine implicit options. But I don't manage to solve the issue of penetration. I have performed a checking of the implicit model, giving two warnings :

 

  ***** WARNING : ELEMENT FORMULATION ISOLID=    0
     IS NOT AVAILABLE FOR STIFFNESS MATRIX BUILDING, USING GENERIC ONE INSTEAD
      POSSIBLE CONVERGING ISSUE. *****

 

and

 

  ** WARNING :IMPLICIT LOADING DATA **

 

Concerning the first warning, I first used the /IMPLICIT option ni the control cards but this gave me a lot of errors as Isolid= 14 in implicit default options and this is not compatible with tetra mesh. So I set it back to the generally default "0" value but it might give "converging issues". Would you know how I can manage this problem ? And if this might cause m y problem of penetration without errors ?

 

Concerning the second warning, I don't understand its meaning, nore did I find any help in the forum about this.

 

Please find attached my engine out file for the implicit checking computation.

 

Thank you in advance for helping me out.

 

Alice

pression_statique_05_0001.out

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Hi Alice,

15 hours ago, Alice said:

***** WARNING : ELEMENT FORMULATION ISOLID=    0
     IS NOT AVAILABLE FOR STIFFNESS MATRIX BUILDING, USING GENERIC ONE INSTEAD
      POSSIBLE CONVERGING ISSUE. *****

Can you try with a different element formulation and see whether the warning is still there?. Normally for 4 node solid tetrahedron there is a drawback of  low convergence. As a workaround, I can suggest you to use 10 node solid tetrahedron element and check.

 

15 hours ago, Alice said:

** WARNING :IMPLICIT LOADING DATA **

 In some cases, RADIOSS does not detect any loading upon part and stops supposing that the input was false.

The suggested workarounds for this issue are:
 

1.Check loading in the model.

2.Increase the initial time step.

3.Creating a slight contact penetration in cases where loading is due to contact.

.

 

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Hello George,

 

Thank you for your quick reply.

 

4 hours ago, George P Johnson said:

Can you try with a different element formulation and see whether the warning is still there?. Normally for 4 node solid tetrahedron there is a drawback of  low convergence. As a workaround, I can suggest you to use 10 node solid tetrahedron element and check.

I have already tried different element formulations but nothing works.

I indeed have 4-node tetrahedron elements. I tried yesterday to change them to 10-node tetrahedrons but did not find how to choose this. How can I tell Hypermesh I want 10-node tetrahedrons ? In a video I saw that Hypermesh gives the choice of first and second order tetra elements but I do not have this choice (see attached word document).

 

 

4 hours ago, George P Johnson said:

 In some cases, RADIOSS does not detect any loading upon part and stops supposing that the input was false.

The suggested workarounds for this issue are:

1.Check loading in the model.

3.Creating a slight contact penetration in cases where loading is due to contact.

Concerning the second warning: my loading consists of a first component compressing a second one; so indeed I have a loading created through contact. In my first simulations I had initial penetration of the contact gap without purpose. This made it work but I have one major problem with this: I have initial loading and this is clearly an outlying result (10^5 N at t = 0, when having 150 N after 0,2 mm compression during real testings).

 

 

4 hours ago, George P Johnson said:

2.Increase the initial time step.

My initial timestep is of 10 for the moment (/IMPL/DTINI = 10), I will set it higher and come back to you.

 

Thanks again,

Alice

 

 

Hypermesh_tetra10.docx

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Hi Alice,In 3D panel, you will get Order Change option where this function can be used to change a group of elements from first  order elements to second  order elements.

Capture.PNG

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Hello George,

 

I managed to change tetra4 -> Brick (degenerated tetrahedron) by unchecking the "match existing mesh box". But would still be interested in knowing how to mesh in tetra10.

I changed Isolid to 17 (what to me seems best) and then to 14 (implicit default value) and both warnings disappear.

However my problem remains...

 

I will come back to you after having checked a higher inital time step and slight initial penetration.

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Hi Alice,

Which HyperWorks version you are using?.In Help Menu>>Click on Updates and System Information and please attach a screen shot of it.

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Hello Geroge,

 

Thank yo ufor the help on second order elements. I am currently running the simulation on tetra10 and will come back to you on this.

 

Find attached the screenshot of the updates information. I use version 14.0

2016-11-30_11h19_53.png

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Hi Alice,

Please update to the latest version HyperWorks 14.0.130.

For the time being, you can use Order Change option to  change from first  order elements to second  order elements.

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