Altair RISE

A program to recognize and reward our most engaged community members

Nominate Yourself Now!

Negative volume error in RADIOSS

Hello All,

I am new to use RADIOSS.

I do not know how to define property card for in RADIOSS for 4 node tetra elements and 8 node hex elements. I have defined ISOLID as 12 and I _tetra as 1 for hex and tetra elements respectively. Remaining fields were not defined.

I have used RBODY elements to connect the parts. When I give run, It is showing error with the message,

MESSAGE ID : 169

** STOP : ZERO OR NEGATIVE VOLUME
FOR 4 NODES TETRAHEDRON ID=121736, INTEGRATION POINT=1

I do not know how to solve this issue. Is there any options/ method to remove this error?

Find more posts tagged with

English

Radioss

Accepted answers

All comments

Altair Forum User

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 )

Please try the run with this option.

Altair Forum User

Hi, I've got the same problem. I'm simulating an dynami impact test with a PP-polymer. I'm getting the same error message for a tetra element due to exzessive compression.

For the material I'm using the PLAS_TAB card with Pressure vs. yield factor function. The maximum failure strain is 180% for tension. There is no failure strain for compression.

Property:

SOLID

Isolid=25

Icrpe=1

Itetra=1

I tried the option Ismstr=2 plus the following input

/DT/NODA/CST
0.9 0.0009
/DT/BRICK/CST
1.0 0.00088 --> even with a relativ high timestep I get the same error message at exactly the same time:

ANIMATION FILE: ********************************************************A012 WRITTEN
6600 5.515 0.7132E-03 INTER 1 1.1% 59.17 143.9 2.196 4.212 0.1993E-01

MESSAGE ID : 169

** STOP : ZERO OR NEGATIVE VOLUME
FOR 4 NODES TETRAHEDRON ID=6580602, INTEGRATION POINT=4

So I don't see any effect on the solution when I'm using Ismstr=2 !?

How can I solve the problem?

Altair Forum User

Hi Eduard,

Please recheck the interface Id 1 defined in the model and also ensure there are no penetrations in the model. By using Ismstr=2 the solid elements will switch to small strain. Please share the model file through the secure dropbox so that we can check the model and suggest the solution.

Altair Forum User

Hi George,

apparently in HW 14 the option Ismstr=2 is only avaliable for hexa-elements. I tried to increase the Pressure vs. yield factor function and to reduce the failure strain to 80% but it was unsuccessfull too. There are no penetrations in the interface. I will upload one of the versions.

Altair Forum User

Hi Eduard,

Relieved the file. We will check this and will update you very soon.

Altair Forum User

Hi Eduard,

Ismstr=2 option is available with tetra elements, with HW 14 version also. Keep Itetra=0 and run with Ismstr=2 option,which is compatible.

The modified files has been sent to you.

Altair Forum User

Hi George,

the model I’ve send to you is simplified. That’s why there are no interfaces. But so far my questions have been answered.Thankyou very much for your quick support

rea2

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 )

Please try the run with this option.

Hi George,

I have the same problem and tried what you described above, but it didn't help. Can you have a look at my model and try to help me find the problem? Thanks in advance!

Edited to add most recent versions, still the same problem.

Unable to find an attachment - read this blog