Necking simulation

[Usimo]

Hi!

I am modelling a necking problem.I want to get the engineering stress-strain curve. My specimen is 20mm length and 5 mm radious. I model the quarter section considering the axissymmetry and symmetry about horontal axis. My abaqus model 20 mm length and 5mm width. I use axisymmetry element CAX4. I applied uniform displacement load. I get my reactions along the node where i apply uniform displacement load. then, I add all the reaction, then divide by the 5mm (assuming the thickness of the model is 1 unit).

I see the necking. but my Stress-strain result seems to be NOT correct.

Plaese anyone advise me about my procedures are correct?

Thanks

Usitha

 

[bassmanjax]

If you're trying to get the nominal stress, then you are not calculating it correctly. I assume that the specimen is a round bar, radius r, that you are loading along it's axis? If so, the load (reaction force) needs to be divided by the specimen area (pi*r^2) to get the nominal stress.



Martin Stokes CEng MIMechE

 

[Usimo]

Wow,

Thank you very much Martin. i apprecite you.

It works. Really I am learning ABAQUS.

This forum is very helpful.

I am going to donate some money for Eng-tips.com. It is very nice.


usitha

 

[Usimo]

I need furher clarificaion.

I am modelling a necking problem.I want to get the engineering stress-strain curve. My specimen is 20mm length and 5 mm radious. I model the quarter section considering the axissymmetry and symmetry about horontal axis. My abaqus model 20 mm length and 5mm width. I use axisymmetry element CAX4. I applied uniform displacement load. I get my reactions along the node where i apply uniform displacement load. then, I add all the reaction, then divide by the 5mm

Now my sress is okay, but the strain seems to be half for corresponding stress.
Should I double the displacement result for this axisymmetric and symmetry about horizontal problem to calulate the strain?


Martin Stokes help me!

thanks