Why do I get incorrect results when I apply inertia loads in the use pass?
The Advanced Analysis Techniques Guide Section 18.104.22.168 has this note:
"If a mass matrix is generated, it is recommended that degree of freedom
constraints be applied in the use pass at the master DOF (defined in the generation pass).
This ensures that all mass is accounted for in the substructure."
In your model, in which you have specified master degrees of freedom
only at the interface between two parts of a cantilever, it is clearly much more
accurate to apply the acceleration in the generation pass so that the load vector
considers all the internal dof of the superelement. A note has been added to the
documentation to clarify this. [Ref: Defect 28447]