How to simulate physics material?

Hi everyone:
I’m trying to simulate a material’s extensibility.
The following video is I’m trying to simulate a plastic object and see how far it can be extended.
I found some material’s parameter from internet, like dynamic friction and young’s modulus. But I’m not sure if it is correct.
Also I’m not sure if Isaac Sim can simulate how far a object can be extended.
As the following video, the object seems can be extended unlimint.
I used Isaac Sim 2022.2.1 version. Anyone can give some advices?

And following video confused me. Why my object can’t extend unless I selected the show the type by deformable body mode and selected the object?

Hi @vic-chen ,
Two observations.

  1. we don’t simulate plastic deformations, just elastic.
  2. for get the proper deformation of the graphics mesh, you need to have sufficient tesselation in all dimensions. Create → Mesh → Settings, choose Cylinder and adjust appropriately.
    image

Hi @SimonPhysX ,
Thanks for your reply, but I still don’t understand how to adjust parameter appropriately .
As the following video, I just simply add a deformable body to a cylinder object.
In the video, I don’t know which one is the real simulate effect.
When I open show by type to check deformable body effect, I think this should be the simluation result doesn’t it?
But you can see when I diselect the cylinder, the simulation effect looks weird.
And as you said, Isaac sim’s seems can’t simulate plastic deformatioin?
So that if I add any physics material to my object, will it have the pyhsics effect?

You need to change the resolution scales in the create → mesh → settings dialog and you will understand :)

Hi @SimonPhysX ,
The following video I try to change the verts scales, but I still have some questions.

  1. Verts scale seems to split my object into several parts?
  2. Does simulation mesh resolution control the object’s softness?
  3. If I want the object more fit the contact surface, should I set more vert scale?
  4. I set a steel physics material to the object, but it looks like not function.
  5. Physics material seems only can simulate friction?
  6. Deformation only can simulation elastic? Is it possible to simulate elastic broken?

Hi,

  1. Verts scale seems to split my object into several parts?
  • Subdividing the graphics mesh just allows it to follow what the simulation is actually doing.
  1. Does simulation mesh resolution control the object’s softness?
  • Yes, lower sim res will generally produces stiffer results. You can also try to increate the iteration count, lower the timestep, or increase the young’s modulus on the material (but usually the problem is that the solver doesn’t converge unless simulation mesh resolution, iteration count and step size are adjusted.
  1. If I want the object more fit the contact surface, should I set more vert scale?
  • Yes, if I understand you correctly. You can increase it in the UI by holding “control” on the keyboard and double click with the mouse.
  1. I set a steel physics material to the object, but it looks like not function
  • A deformable body is not going to work well with a really rigid material.
  1. Physics material seems only can simulate friction?
  • Not sure what you mean. If you mean that you don’t get the correct stiffness, see answers above.
  1. Deformation only can simulation elastic? Is it possible to simulate elastic broken?
  • Yes, we only support elastic materials, no plastic deformation.

Hi @SimonPhysX ,
Thanks for your answer. Hope one day that omniverse can simulate other physics materials.
Best regard with you.

Hi @SimonPhysX ,
About my 6th question, you said that omniverse currently only supports elastic materials. The following questions I wanted to understand.

  1. If I give a cylinder with an elastic material, can I simulate how far it could be?
  2. Is it possible to give a limit length to see if the elastic material will be broken or elastic fatigue?
  3. If Omniverse can do the above questions, the simulation result can be digitization?

Hi @vic-chen,
I will need some more information on what you are trying to achieve. There is no built in deformation limit or anything like that. However you could try to add plasticity yourself by changing the rest shape at runtime, but currently we don’t support that. We will likely add that soon. You would need to recreate the deformable in the deformed state right now.
Regarding your question 5. did you make sure to create a deformable body material?
Cheers,
Simon

Hi @SimonPhysX ,

  1. We want to simulate if we give a cotton thread(or other materials) 5cm with setup cotton thread Young’s module. How far it could be extended?
  2. If the cotton thread only can be extended by 5cm, when we extend it to 6cm, could we see it broken at Isaac Sim or get data information to know it broke?
  3. Can physics material simulate the elastic fatigue effect?

@vic-cheng
Unfortunately there is no support for plastic deformation or tearing right now.

Thanks for your help!
Best regard!

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