** RUN KILLED : ENERGY ERROR LIMIT REACHED

antonio.dortona95

Hi,

Sorry for my question but I'm searching for advice. I have some errors with 'run killed', energy and mass. I have also errors with 'WARNING ZERO OR NEGATIVE VOLUME' and these elements belongs to the honeycomb. I think that these errors appear because I didn't defined a failure strain but I prefer to not define this paramater. Am I right? How could I solve these problems?

Thanks for attention

Best regards

 

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Simon Križnik

Hi,

 

Sometimes with soft material, solid elements can be deformed severely that its nodes go through opposite side and cause a negative volume. 

'ZERO OR NEGATIVE VOLUME'  warning happens when solid elements are very deformed and their characteristic length goes to 0. For large strain formulation the time step of an element goes to 0 when the element is compressed. 

In RADIOSS Starter input file (Runname_0000.rad), use Ismstr =2 in the solid property and in RADIOSS Engine file (Runname_0001.rad) use the option/DT/BRICK/CST which will set the time step value tmin at which the solid elements will switch to small strain. (/DT/BRICK/CST option is used to control the time step of the analysis. The time step becomes constant after reaching Tmin specified by the user )

 

You should define failure criteria to avoid zero or negative volume and obtain more realistic results.

 

From the engine out file it looks like the energy error goes to 99% at cycle 500 and contact interface ID 3 is controlling the timestep from cycle 600-800.

 

Maybe I will remodel with node to node connectivity if I have more time, until then please check the following tutorial:

https://altairuniversity.com/learning-library/modeling-and-analysis-of-honeycomb-impact-attenuator/