Learning Forum

[Feroz Basha]

Hello Everyone, I am trying to model a contact in Transient Structural Analysis and having stability issues. Here is the problem that I am trying to simulate. I have a fabric material (0.5mm thick and 0.3m x 0.2m size) at 5 mm above a solid steel block of size 0.3m x 0.2m x 25mm. All sides of the fabric material and the bottom surface of the steel block are fixed. I am using the Mooney-Rivlin material model for the fabric material.
If I apply only gravitational force on the fabric material, it sags as it is supposed to, comes in contact with the steel block, and remains stationary. However, if a apply a very small pressure (say 10 Pa) on the surface of the fabric (along with gravitational force) the solution diverges and gives an error message “Element 1219 located in Body "Membrane" (and maybe other elements) has become highly distorted.”

Here are a few exercises that I did (all are crashing at different stages of the simulation).
1) Tried frictional and frictionless contacts.
2) Tried different values for stabilization damping factor.
3) Applied a constant pressure and also linearly varied pressure starting from zero.
4) Tried different time steps (lowest time step used was 0.0005 seconds)

Here are a few other settings that I used:
1) Large deflection option is on.
2) Physics Preference for Mesh is Nonlinear Mechanical, and
3) Element order for mesh is linear. Attached is an image of the setup.

I modelled only the fabric material (without the steel block and without the contact) for different values of applied pressure and the fabric deflected properly and gave stable results.

I am trying to conduct a fluid-structure interaction (FSI) simulation of fluttering fabric material. While fluttering, the fabric will come in contact with a solid surface. Therefore, contact modelling with applied pressure is vital for our simulations.

Any guidance on how to model this problem will be greatly appreciated. Thank you.

[Akshay Maniyar]

Hi Feroz,

Please check the below video on the element distortion issue and try to use the various suggestions mentioned in it.

How to Handle Element Distortion Errors in Hyperelastic Materials — Lesson 3 - ANSYS Innovation Courses

Thanks,

Akshay Maniyar

[Ashish Khemka]

Hi Feroz,

Please see if the following link helps you: FLAG simulation – intend to make the fabric drop under gravity (ansys.com)

Regards,

Ashish Kumar