Uniaxial compressio...
 

Uniaxial compression test modeling with implicit solution  

 

csuznxg
(@csuznxg)
Active Member
Joined: 3 months ago
Posts: 12
March 19, 2020 2:38 am  

Hi,

I am working on the uniaxial compression test modeling with implicit solution. And I used cohesive elements for fracturing modeling in this model. Here is an issue that no d3plot file outputted because of the lots of cohesive elements failed in a very short time. The Message file shows that many iterations and negative eigenvalues happened during the cohesive elements failing. 

Could you please tell me how to improve my model? 

Some parameters may in regard to the d3plot file outputting are listed as follows,

*DATABASE_BINARY_D3PLOT        dt=0.1
*CONTROL_IMPLICIT_GENERAL      dto=0.1

*CONTROL_IMPLICIT_AUTO      dtmin=0.01   dtmax=1

*CONTROL_TERMINATIO    endtim =200s

I tried to define variable time intervals for d3plot outputing, but is doesn't work.

Thanks

1584585483-ucs.png

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Negative Volume
(@negativevolume)
Estimable Member Admin
Joined: 1 year ago
Posts: 190
March 27, 2020 2:45 pm  

Hi @csuznxg

This is strange. I would try running a test simulation without any motion of the top impactor and see if the same thing happens. Theoretically, no elements would fail if there is no load, so if you are still having issues then we can isolate the problem to your model itself. 


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csuznxg
(@csuznxg)
Active Member
Joined: 3 months ago
Posts: 12
March 27, 2020 3:26 pm  

@negativevolume

Hi, thank you very much for your kind reply. I tried some models with elements failure in implicit solution. For the fracture toughness and Brazilian splitting modeling (a small amounts of elements failed in the center line), my model works very well. For UCS modeling, many elements would fail, the calculation becomes unstable. I followed a tutorial (

) and treat the UCS modeling as a quasi-static condition. Finally, I got a stable calculation in an explicit solution with loading rate increasing method.


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