Linear perturbation support is now available for buckling analysis, full harmonic analysis, and for subsequent mode-superposition, PSD, or other type of modal-based linear dynamic analysis.

In many engineering applications, the linear behavior of a structure based on a prior linear or nonlinear preloaded status is of interest. In addition to prior support of linear perturbation modal analysis, you can now use the linear perturbation analysis procedure to solve a linear problem from this preloaded case for eigenvalue buckling analyses and full harmonic analyses. The preloaded case can include any nonlinear materials and geometric and contact nonlinearities. The linear perturbation full harmonic analysis also supports cyclic symmetric and VT full harmonic options.

To perform a linear perturbation buckling or full harmonic analysis after a static or full transient analysis, restart the analysis at the load point of interest, apply your perturbation load, and then use the PERTURB and SOLVE commands to execute the linear perturbation analysis.

A new option for linear perturbation uses the tangent (material Jacobian) on the material constitutive curve as the material property. The material property remains linear in linear perturbation and is obtained at the point of the base analysis where restart occurs. The option is primarily for nonlinear materials other than hyperelastic materials. For more information, see the documentation for the PERTURB command and Specifying Material Behavior in Linear Perturbation in the Element Reference.