## Materials

#### Help on a problem about steel ball on top of a rubber materials simulation

• aptorres27
Subscriber

Hi all,

I am trying to simulate a steel ball on top of a rubber materials (hydrogel/gel) simulation on APDL and I have a couple of questions, or perhaps someone could guide me on what to do.

What I am trying to simulate deformation of rubber materials in which the steel ball is put on top of a hydrogel/gel that is made up of elastomers (PDMS, PDMS/PEG, Natural Rubber, etc). The idea is that as time goes by the steel ball will deform the hydrogel and the hydrogel experiences creep. I've done preliminary runs and I set up a Mooney-Rivlin model for the rubber materials and I set the steel ball to be elastic linear isotropic.

In my first run, I applied structural displacements and then I did load steps opts and write LS files (The result of my displacement is shown in the picture. However, I think it is important to add the weights of my objects. My first question is, how do you add the weights of your objects? Secondly, Do I need to?

How do I simulate creep? What do you guys think? Any tutorials/books do you recommend?

• peteroznewman
Subscriber

When you say a steel ball is "put" on top of a material, that is not described with enough clarity.

Do you mean the ball was initially tangent to the surface and a displacement was applied?

What you could do instead is simply turn on gravity and let the weight of the ball push down on the material.

• aptorres27
Subscriber

Initially, it is in contact to the surface. The weight of the ball is what causing the deformation of a hydrogel in some amount of time. How do you set the weight for the the steel ball? How do you turn on gravity?

• peteroznewman
Subscriber

The weight of the steel ball is determined by its volume and density.

Gravity is an acceleration load. Look up in Mechancial APDL the command for applying an acceleration load. The value is 9.8 m/s^2 upward. That will push the ball down into the hydrogel.