The response in a linear perturbation step is the linear perturbation response about the base state. The base state is the current state of the model at the end of the last general analysis step prior to the linear perturbation step. If the first step of an analysis case is a perturbation step, the base state is determined from the Initialization step. Nonlinear geometric effects are not considered during a linear perturbation step. You can add linear perturbation steps only in structural analysis cases. You can include linear perturbation steps between general static analysis steps; the linear perturbation response has no effect as the general static analysis is continued. The step time of linear perturbation steps, which is taken arbitrarily to be a very small number, is never accumulated into the total analysis time (the total accumulated time over all general analysis steps within a particular nonlinear structural analysis case). During a linear perturbation analysis step, the model's response is defined by its linear elastic stiffness at the base state. Plasticity and other inelastic effects are ignored.
Abaqus for CATIA V5 provides the following linear perturbation steps:
Static perturbation
Frequency
Mode-based steady-state dynamics
Subspace-based steady-state dynamics