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ABAQUS pore metal compression

Submitted by IMOTEC on

Hi,

I am trying to model a compression test for aluminium. In my model I have a 2D rigid plate and a 2D deformable part. And also my part have some space in itself. I used dynamic explicit step with 0.01 time period. It also run somewhere. But then exited with an error. It has some convergence diffuculties. I also tried to adaptive mesh but it gave me same error early. Also I can see the result of solved part and I looked reaction force. I saw too much oscilation for force-time graph. Can anyone help me to solve this problem. I also attached the inp file of model.

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mswan

Hello,

Without actually running your code to look at your geometry or to figure out exactly what you're doing, I would suggest that you look into ramp-loading your sample. In my experience (which might not be applicable in your situation), I've found that having a linear displacement boundary condition in an explicit simulation causes a bunch of ringing (waves bouncing around) in the body that can often cause the simulation to halt. Try a quadratic displacement BC (at least for the initial load from zero-stress to slightly stressed) and see if that fixes your problem.

Also, remember that when you shrink your mesh you also need to shrink your timestep. It's generally a good idea to have your timestep limited by the CFL condition (https://en.wikipedia.org/wiki/Courant%E2%80%93Friedrichs%E2%80%93Lewy_c…). For example, simulating copper with a longitudinal soundspeed of ~13000 m/s and using approximately 1cm elements, you would expect a timestep no larger than 7.7e-7 seconds. It seems like your 0.01 seconds might be too large?

Mon, 12/28/2015 - 16:18 Permalink
IMOTEC

Thank you for your interest. In my problem I applied displacement with smooth amplitude. But before this I tired velocity BC and also small time step. But part did not deform which I want. And kinetic energy increased with smaller time step. But you are right the wave speed in metal is 5000m/sec. My purpose for this problem is to simulate compression of aluminum part with some space in it. This model may not be figure out my problem. But it nearly same and simple model. When I try to decrease step time I take errors below;

The elements contained in element set ErrElemExcessDistortion-Step1 have distorted excessively.

There is only one excessively distorted element

The ratio of deformation speed to wave speed exceeds 1.0000 in at least one element. This usually indicates an error with the model definition. Additional diagnostic information may be found in the message file.

The elements contained in element set ErrElemExcessDistortion-Step1 have distorted excessively.

Last thing, I did not understant what you mean with quadratic displacament BC.

I will wate for your help.

Thank you!

Mon, 12/28/2015 - 18:33 Permalink