Learning Forum

[wasif.safdar]

Dear all,

I am trying to do an tensile test of rubber using MAT OGDEN. I gave an average engineering stress strain curve from the experiments as an input to the material model however as you can see below the simulation (dashed line) becomes unstable after around 200 percent of the strain however the experimemts go upto about 700 percent. How can I make the simulation more stable so that it continues to run for larger strain values?

The error in the d3hsp does not say anything regarding an error and simulation just terminates normally even though in the post processing it seems like the simulation has crashed and no shell elements are visible. Here is link to the .k file https://drive.google.com/file/d/1EY1ONK1fZBb6abfN0u63SDJ6mYYWF4wm/view?usp=sharing

Kindly let me know if anyone has an idea. Thanks in advance!

[Pedram Samadian]

Hi Wasif,

Why is stress nonzero for zero strain in the experimental data? You can find some tips below to improve your model predictions:

• Use a finer and higher-quality mesh in regions of high deformation to avoid numerical instability.
• Consider using fully integrated elements (type #16 shell with a hourglass type #8) to reduce numerical instability at large strains. 
• Reduce mass scaling if applicable to maintain stability without affecting results.

I hope this information helps.

Thanks,

Pedram

[Nanda Veralla]

 

Hello Wasif,
Ansys Employees are not allowed to download and access any software files users upload. So, for better support, try to insert images as much as possible to explain your problem. 
Thanks,
Nanda

[wasif.safdar]

The experimental curve starts from a non 0 value because I removed the initial part where the values fluctuate around 0. Ofcourse one can start from 0.

With regards to your suggestions, they did not help really. I still get erros like:

Also, in the beginning I see a warning message that says:

Best,
Wasif