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Linear perturbation & Contact

Linear perturbation & Contact

Linear perturbation & Contact

(OP)
I am using Abaqus/CAE v6.11
Using linear perturbation-frequency step to determine natural frequencies of a flexible Wing. Constant cross section ribs stacked to form a very flexible wing. A single 'spar' rectangular rod is inserted thru these airfoil sections. Picture shishkabob or cantilever beam. The root rib BC is fully fixed.
Trying to figure out limitations of contact interactions within the linear pert-frequency step. Specifically, trying to prevent overlap during deflection. When using interaction (general-std), it prevents all normal separation between the rib sections. It acts like a slip tie. This is too rigid. The contact feature works fine if I create a static step, but not during lin pert. Ive tried contact initializations, surf thickness, etc... All of which overconstrain the parts by resisting normal deflection separation.
Any suggestions? I'm going to try gasket element next.
Thank you for your time,
Doug

RE: Linear perturbation & Contact

(OP)
In addition, i am running the Linear pert-frequency step directly after initial base step.
I found this feature which I could not get to work by editing the INP file...
34-2.1-10 *surface interaction, tracking thickness=value
It kept aborting saying there is no step defined.

Thank you,
Doug

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