Hi Marcin,

Your question does not include much information. Please answer the following:

1) How complex is the elastic rheology?

2) How complex is the viscoplastic rheology?

3) Will you be writing a UMAT or using inbuilt options within ABAQUS?

4) Will you be using a fixed (Eulerian) or moving (Lagrangian) mesh, or some form of mesh smoothing?

5) Are you working in 2D or 3D?

6) Which version of ABAQUS will you use?

By answering the above, your question will receive more attention.

Best regards,

Milan.

Thanks Milan.

An example of the behaviour you can find in the attached plot. The dog/bone shape specimens were tested at different loading rates, the plot shows results at one rate. The behaviour is rather simple, the elastic part is rate dependent, as well as yield stress.

I would like to create a simple bilinear model - viscoelastic perfectly plastic with ductile or brittle failure. I found out, that viscoelastic model in Abaqus doesn't work with any plasticity, therefore I am looking at two-layer viscoplasticity model available in Abaqus.

Can you recommend any other in-built options, or UMAT is only solution?

Thanks,

M

Hi Marcin,

What range of strain rates will you be simulating? If the range is quite small, you can define a 'solution dependent field variable' to be equal to the local strain rate. Then you can set the Young modulus to be a function of that field variable. This method is a form a explicit dynamics, and this approach will give rise to oscillations in your stress field if the range of rates you simulate is quite large. However, it should be OK if the range of rates is small. Examine the stress field in successive time increments to see if the Mises stress oscillates.

Otherwise, a UMAT is the only option I know of. You can write one or purchase a UMAT library for a very low annual price from Veryst Engineering in the USA. Ask for Jorgen Bergstrom or Nagi Elabbasi (they are both very helpful) but if you contact them, do mention my name too.

Best regards,

Milan.

Hi Milan,

I was testing the samples at 1, 10 and 100 mm/min.

Thank you, I will look into this topic and test the approach you mentioned.