Now I’m working on the school project and interested to use the Prepomax to simulate for the system consist of a circular surface loaded by a mass.

For the setup, I design a flat circular shell part by consider the effect of damping. However, I’m not sure how to set all constraint to simulate the shell motion using modal dynamics with Pre-loaded steps. So I’m not sure can modal dynamics allowed to use with the shell part or not? If able, could I have any advise please?

For modal dynamics, only the first point from there should apply. So it should be normally doable. The setup depends on what exactly you want to achieve. When it comes to the excitation itself, you can apply a force load, use mass section for added mass or even define base motion (special boundary condition type for linear dynamics) via Keyword Editor.

To simulate the preload, you will need 3 steps - Static, then Frequency with Perturbation and Storage enabled and Modal Dynamics.

Set material > Density = 14.96 kgm^-3 and Poisson’s ratio = 0.38

Sections > choose circle shell upper face

Constraints > Only set for surface spring

Steps >> including Frequency step and Modal Dynamics step (frequency step: number of frequency = 5, storage = YES and modal dynamics step: damping type = constant =0.063 → load = 0.13 N)

Can you share the .pmx file (upload it on some hosting website and paste the link here) ? The setup looks good in general but the devil is in the details. If you want to define sort of elastic foundation for the circular plate, check this video: https://www.youtube.com/watch?v=ZB49UD6xElo

The another problem that I’m facing through is when I change the force applied to the interface, there was nothing change such as frequency as well as deformation scale factor. How could I fix it?

Hi again, I would like to ask how to get the modal dynamics damping “plot” based on a circular shell loaded by an amount of force? For now, I’ve already achieve the simulations graphically, however, the dynamics plots were not shown in the simulation results. What should I do?

What kind of plot do you mean - XY curve ? With what variables ? Force vs displacement or something like that ? You already have U (displacements) requested as history output - that’s the right way. You can also request RF to have reaction forces.

You assigned the history output request to a reference point which is not used for anything (any rigid body constraint) in the model. Reassign it to some node belonging to the mesh in the model.

Also, enable Storage for the first step to make the second one work properly.