A model from Workbench Simulation 11.0 is brought into ANSYS Classic and it fails with a constraint equation error unless NSUBST,1,1,1 is used:
*** FATAL *** CP = 9.438 TIME= 18:35:24
A term of constraint equation 13 is not defined, most likely due to a
displacement constraint on this or an adjoining constraint equation.
The model has MPC contact, but the nodes are not restrained via the D command, and there are no constraint equations in the model (other than the internal ones from the MPC contact). It seems running a
nonlinear analysis causes the MPC contact to fail, but it works for a linear analysis. Is this a known error?
Yes, Defect 65275 was filed and corrected in the 12.0BETA UP20080229 build of ANSYS. Development noted the following about the error:
The error was due to the way we were storing the constraint equation numbers based on nbce (an internal variable). This variable was being reset in a manner that contradicted the code in the mpc184 routines under certain circumstances as this problem. An alternative storage scheme has been set up to correct this error.