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[Praveen95]

Dear Ansys Community,

I am getting this warning message when I try to run the structural part of the transient thermal-structural problem. Please tell me where is the problem. It is not letting the convergence to happen quickly.

 The equivalent plastic strain increment has exceeded the specified limit value. Since the time increment has reached the minimum value, the iteration is continued with the minimum time step used.

Best Regards

Praveen

[Aniket Chavan]

I think that means that you need to reduce the minimum timestep even further in your analysis settings.

-Aniket

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[Praveen95]

Dear Aniket,

 

I have reduced the minimum time step to 1e-3 sec for each step having 10sec. But still I am getting this note as shown below:

The incremental plastic strain computed in this iteration is larger than the criterion of 15% leading to bisection.  You may try  incrementing the load more slowly by increasing the number of substeps  or use the CUTCONTROL command to re-specify this criterion

Should I decrease still more, because it is taking soo much time?

Best Regards

Praveen

[Aniket Chavan]

It is very important to build up the FSI simulation in stages as opposed to setting up the 2-way FSI right at the start. This document "Best Practices for Coupled Fluid-Structure Interaction (FSI)" describes this process and is available here: https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v201/en/sysc_ug/sysc_bestpractices_fsi.html
 
FSI simulations with very soft materials are prone to numerical instabilities. In 2020R1 we have introduced a stabilization method in System Coupling called the Quasi-Newton Stabilization Algorithm. This will very likely need to be used for your case. More information here: https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v201/en/sysc_ug/sysc_gen_scservice_dt_supplemental_iqnils.html
 
Please check if that helps!
 

[Praveen95]

Dear Aniket
My model is only structural and no coupling between fluid and strukture is involved.
The materials involved are Epoxy Resin and Copper metal. So please suggest me should I need to use FSI?
I will go through the link you suggested

Best Regards
Praveen

[Praveen95]

I am using doing two simulations 1. with coupled transient thermal and static structural. Here there are 13 steps with 1000 sec as the time step. I vary the temperature cyclically, like 22,180,180,-40,-40,180,180,-40,-40,180,180,-40,-40,22
2. Another, I am doing only static structural with thermal BC with 13 steps with 10 sec each. I vary the temperature cyclically like 22,180,180,-40,-40,180,180,-40,-40,180,180,-40,-40,22.

I want to compare both

My doubt is if I give 2 days for HPC, it will give result. But the mesh is having 300000nodes and 100000 elements. I think this is not sooo fine to take this much time.