What does an "Element process ID" reference to in Optistruct?

Hello,

 

I have not been able to sucessfully finish my analysis because of a fatal error.

 

.OUT file says the following  error

 

'1 error have been detected in element processing procedure in processes with id = 5. Plese check the corresponding out file for details.'

 

What is a process ID? I have encounter this error before with differtent id numbers, but have not figured out what it means.

 

My model contains Hinge joints and is a NonLinear quasi-static analysis.

 

Thank you for your help.