abaqus rubber compression and surface strains help!

[mollam80]

hi guys

I am kind of new this abaqus package. I have a couple of questions:

1) I am modeling compression of a rubber. I have to go stretch values of 0.2 (h/H=0.2) here h, H are initial and final length of specimen. But code is quiting around 0.5 how can achieve higher stretch? changing incremental step size or what? going with finer mesh? please give some advise.

2) I want to see surface strains. I am using axisymmetric model so surface is corresponding the edge of the axial plane. is it enough to extract surface strains or should i go with a 3D model to see the surface strains?

3) how to extract surface strains as the rubber is bulging under compression? basically for a selected point on the surface I want to see the evolution of strain components as compression progresses. this can be strain vs. frame number. where are the strains stored? how can I access them? should I write scripts or this can be done with some cae functionality?

and strains are log strains so true strains right? are there lagrange strains? I could not find them on the plot menu.

4) if I have to use scripts could you give some starting point or clue a basic knowledge so that I can start to play with it and advance from that position?

thanks.

 

[craigj]

step 1 first.

- What is the material you are modeling, and what model are you using? You should be using a hyperelastic one...right? Do you have material data? What modes of strech do you have? Marlow is a stable model, but only uniaxial data and calculates the other modes.
- What element technology are you using?
- Have you turned on nonlinear geometry?
- What reason do you get from the solver for non-convergance?

 

[mollam80]

thanks for reply

I am using hyperelastic mooney rivlin. I curve fitted to the uniaxial compression data and found those c1 and c2 constants. I equate D1=0 for incompressibility. Actually mooney rivlin fits quite well.

I am using hybrid elements (because incompressible) C3D8RH.

yes nonlinearity is on.

I was getting excessive distortion error and then increment number was reached. I think if I allow it to go for smaller increments it can handle it. I was trying to get some quick results may that was the fault. anyway I was in a rush yesterday night I figured out step 2 and 3 from xy plot creation section.

but for step 4 I need advice.

my question is how can I extract raw data from abaqus: like strain history of a node? or stress vs strain of a node? How can I get it like in excel or in notepad so that I can further process it? could you please provide some information?

thank you very much.