Can Prepomax able to simulate mass-spring-damping for shell part?

General Questions
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1

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?

2

There are some issues with shells in steady-state dynamics analyses: Utilities to handle ccx issues with shells in steady state dynamics

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.

3

These are the setups that I’ve made for my model

  1. Node set > for the shell boundary and face.
  2. Reference Point > Set at the center of a circle
  3. Set material > Density = 14.96 kgm^-3 and Poisson’s ratio = 0.38
  4. Sections > choose circle shell upper face
  5. Constraints > Only set for surface spring
  6. 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)

Screenshot 2024-07-18 195636
Screenshot 2024-07-18 1956361919×1126 177 KB

In case my model is such an elastic fabric(not rigid), what should I do?

4

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

5

Here is the google drive link for the .pmx file

6

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?

7

Are the dimensions of the model (and other input units) correct ? The diameter of the plate is around 2000 m.

1 Like
8

Got it!! Thank you

Screenshot 2024-07-21 083248
Screenshot 2024-07-21 0832481919×1128 236 KB

9

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?

10

here is the file for the recent edited

11

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.

12

I mean, the U(displacement) doesn’t show any change in displacement over time. Where should I look for the displacement vs time plot?

13

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.