When running SOL 128 - nonlinear harmonic frequency solution - I get a FATAL message that there are no nonlinear degrees of freedom defined. How do I define these?
See Below Requirements for SOL 128 and its functionality.
User Interface
Frequency dependent loading for SOL 128 can be applied through standard forcing functions available in MSC Nastran or through the unbalance loads in case rotors are present in the model.
File Management Section (FMS)
One modified FMS entry, related to the SCA UDS (Service Component Architecture User Defined Subroutine), is required if a user defined service is to be used. When a user defined service (UDS) is to be used to describe the behavior of the NLRSFD type nonlinearity in nonlinear harmonic response, the FMS CONNECT entry is used with the SERVICE qualifier to make the connection between the GROUP name on the NLRSFD bulk data entry and the name of the external service.
Executive Section
Nonlinear harmonic response is available as SOL 128 or SOL SENLHARM. This is a complete solution sequence based around linear frequency response (SOL 108) in which nonlinearities may be taken into account.
Case Control
The case control entry NLHARM has been added for nonlinear harmonic response to reference the NLHARM bulk data entry. The existing NONLINEAR case control entry, previously dedicated to transient response analysis, may now also be used in nonlinear harmonic response to reference nonlinear force bulk data entries (NOLIN1, NOLIN2, NOLIN3, NOLIN4, NLRGAP, NLRSFD).
NLHARM
The NLHARM case control entry is dedicated to nonlinear harmonic response; it is used to reference a bulk data NLHARM entry.
NLHARM=n
where n is the ID of the NLHARM bulk data entry.
NONLINEAR
The existing NONLINEAR case control entry, which was previously dedicated to transient linear and transient nonlinear analysis, may now be used in nonlinear harmonic response analysis. The NONLINEAR case control command is used in exactly the same way in nonlinear harmonic response as it is in transient response to refer to the collection of nonlinear force entries (NLRGAP, NLRSFD and NONLINi).
