I am trying to simulate the effect

[pjuneja]

I am trying to simulate the effect of gravity on an object (breast). The breast under-goes large deformations because of gravity, the pendulum length of breast almost doubles between the positions am interested in.

So far, I could simulate homogeneous (single domain breast tissue) breast models using Static, General analysis

Next step in my work is to simulate heterogeneous (multi-domain, fat and fibroglandular tissue, surgical clips etc) breast models. In this I am having difficulty in getting converging solution. Initially I got an error that "Too many increments needed to complete the step".

After searching at forums and reading in ABAQUS analysis user manual, I have tried to change few things such as:
1) Step>Other>Control parameter> Increment Step> Discontinuous and >more IA 20 instead of 5.
2) Stabilisation options with default
3) Static, RIKS method

None of these had any effect. The analysis still slows down, increments becomes of order 1E-5 at about after 30% of the step (total time step 0.30).

Attache is the input file. Any comments/ suggestions how to resolve this?

Thanks
Prab

 

[IceBreakerSours]

1. What makes you think changing control parameters will solve the problem? What are these control parameters? What is their purpose?
2. Why should stabilization resolve it? What are the pros/cons of stabilization?
3. Why use the Riks method? What is the RIKS method? When should you use it?

Too many increments needed to complete the step

Again! This is just a symptom, not the cause of non-convergence. So, whatever you have tried has little or no relevance to the problem at hand. You've even tried explicit analysis when the real problem was with the amplitude definition.

You are using a tool (i.e., FEA) that you do not understand. I strongly suggest learning the basics before randomly trying things. Otherwise, have someone else (consultant, for example) do the project for you.

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[pjuneja]

You are not being helpful

 

[MechIrl]

The strains in some of your elements when it fails are over 100%. This is almost certainly your problem. You could address it by using more realistic boundary conditions or maybe a better mesh in the highly deformed region. I don't think you can use adaptive meshing for your problem. Stabilizaiton/Riks method etc. are nothing to do with addressing your problem.

 

[IceBreakerSours]

Half a year ago, it was pointed out that the mesh may run in to issues (here). As MechIrl notes, the problem lies entirely with the mesh quality. Moreover, there are several locations where two materials occupy the same volume, which makes no physical sense.

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[pjuneja]

Thank you I will try to fix the issues.