What is NLMAX in nastran?

[Venkat133]

Hi,
When I wanted to run sol 109 direct transient analysis in nx nastran the message showing that 'during detection of massless mechanism the number of singularities found 6435 which is greater than NLMAX 60, increase the value NLMAX.' in solution monitor. However I got the solution file but my doubt is that was the results are correct? Please clarify my doubt.

 

[JBlack68]

you don't say which version of Nastran you are suing. Anyone reading the QRG will find something along these lines

The number of suspected massless mechanisms is determined from the number of high ratio messages. If this number exceeds NLMAX, the number of trial massless mechanisms is reduced to NLMAX. This is a means to avoid an expensive run when there may be thousands of massless mechanisms due to modeling errors. The value of this parameter may be increased on initial runs where it is possible that there are many high ratio DOFs in order to see them all at once

so there is a good chance that errors exist in the model and therefore one would be "highly" suspicious of any results obtained.

 

[dfreire]

IF you set PARAM,BAILOUT,-1 the model will run and, then, it is easier to debug your model because you can see if some part of the model are loose, for example.

 

[JBlack68]

SOL103 will show all the rigid boy modes

 

[Venkat133]

Thank you for giving your valuable suggestions. In my model I don't have any element errors and you said that 'there is a chance of errors' so what type of errors' it may have. And one more doubt is what is massless mechanisms.iam using nx12

 

[dfreire]

Maybe this thread could help you: thread1234-334952

If not, if you explain a little your model we can think about it.