Hello,

I am trying to find the natual frequency of a rectangular membrane using ABAQUS.

I have applied the pre-stress on the membrane using the 'Shell edge loads' and turning on the 'NLGEOM' option. Now I have to include an initial displacement in the membrane which adds to the pre- stress already applied.

I need some help on how can the initial displacement be applied to the membrane. Only the amplitude of displacement is known and not the force causing it. Also, the effect of the displacement should add to the initial tensions and this effect should be included in the frequency calculation step.

Woud be grateful for any input on this issue.

Thanks.