Simcenter 3D Solutions Simcenter 3D error in SOL 111: SYSTEM FATAL MESSAGE 7340 (LNNHERR)
Summary
SOL 111 with several DMIGs in Simcenter 3D and Nastran fails with the following error. How to troubleshoot this? *** SYSTEM FATAL MESSAGE 7340 (LNNHERR) PROCESS ERROR REPORTED BY SUBROUTINE LNNP2CS (IER= -735) USER INFORMATION: NEGATIVE STURM COUNT BETWEEN SHIFTS. *** SYSTEM FATAL MESSAGE 7340 (LNNHERR) WARNING REPORTED BY SUBROUTINE LNNDRVS (IER= 735) USER INFORMATION: NEGATIVE STURM COUNT BETWEEN SHIFTS.
Details
When DMIGs are present in the model, they should be in the same units as the main model. If not, part of the model is stiffer than the rest and can have thousands of modes. One should look at the shift information in Lanczos and if there is a large number of expected modes, Lanczos breaks down as it tries to check if it didn't miss any modes using something called Sturm sequence check. In this example, a specific unit system is used while solving for the DMIGs so setting the same unit system to the deck of the main model that Nastran writes out (RMB on solution -> Edit Advanced Solver Options -> General -> Output File Units - see the screenshot below for reference and note that the Output File here means the *.dat deck shown in the File Name field and not the *.op2 results file we get after solving) ensures consistent units and resolves the error mentioned above.