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hi. i am trying to do a simple problem by myself. i want to perform the movement of fluid inside a steel box. i have read some tutorial in Help file and attempt to do the same as what i read. But my hm seem to be wrong somewhere. i can not run it correctly. could anybody please check my hm file? thanks

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Altair Forum User

Hi Toan,

The run is terminating due to negative volume error. This NEGATIVE VOLUME error 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.This means that the solid elements using Ismstr =2 will use large strain formulation while their time step remains greater than tmin, and will then switch to small strain formulation.

(/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 )

 

Meanwhile I strongly recommend to recheck the model created. There are many  incompatible kinematic conditions warnings reported in the starter out file. True incompatible kinematic conditions  can generate energy and local instability which can result in weird behavior of the model. Please try recreating the model.