The volume of 390 elements is zero, small, or negative

[llegis]

Hello everyone,

I am an eager reader of your forum and it has helped me a lot in getting to know more about Abaqus and solving uprising problems. But now I have encountered a problem that I couldn't fix.

I am running two sequential analysis - one static and one linear perturbation. I have linked the two analysis with an initial state field. The static analysis works flawless and the frequency analysis on it's own too. But when linked together the frequency analysis aborts with the error:

The volume of 390 elements is zero, small, or negative. Check coordinates or node numbering, or modify the mesh seed. In the case of a tetrahedron this error may indicate that all nodes are located very nearly in a plane. The elements have been identified in element set ErrElemVolSmallNegZero.

The identified elements are not tetrahedron but hex and are all at the outer surfaces of my air domain (where I have defined acoustic infinite elements).
Removing the acoustic infinite elements leads to the system error 29539.

Previously I successfully constructed a dummy case with this exact sequential analysis without any of this error messages.

Can somebody please help me? It would even be acceptable to suppress information from those 390 elements since they are not in my region of interest.

Thank you in advance for your time and help.

 

[portliner]

I use to run the static and linear pertubation on the same model like:

Static step:

*Static, nlgeom


Linear pertubation step:

*Frequency,

OBS! you mnust use the suboption "nlgeom" to make the stresses being taken into account in the linear pertubation step!

 

[llegis]

Thank you for your answer portliner

After several days of trying I went back to my working dummy model, changed all geometries, constraints, etc. and complicated the problem step by step. It's now perfectly working! I don't know what I did differently in the dummy model though.

The sequential analysis seemed the best solution for my problem. In the static analysis the pressure load is created by the acoustic pressure calculated from the frequency analysis. I run the cycle until it converges.

 

[rstupplebeen]

I find a good text editor with a comparison to be a good tool to determine what is different in the *.inp files. I hope this helps.

Rob Stupplebeen

https://sites.google.com/site/robertkstupplebeen/