Andreas Burger's blog

Hi,

I've been trying to apply a displacement to a body in an implicit model using equally spaced amplitudes.

Hello,

I am running a simulation where I have a rigid body (shell elements) pushing into a deformable part.  Unfortunately, the simulation aborts with the following error:

The dot product -0.19758 cannot be negative for element 30050 instance xzy with record ID 844 at step 2 inc 1 kitgen 5.

This element (C3D4H) belongs to the deformable part and is within the body, so no not close to the contact at all.  At the point where the simulation aborts, this element is not deformed and the stress is basically 0 (E-6).

Normal
0

false
false
false

MicrosoftInternetExplorer4

Hi,

I'v been using the Abaqus command window to run my jobs without any problems.

Today, however, I suddenly got the following message:

Hi,

I am in the process of debugging a UMAT.  In my UMAT code I am currently using write statements to output certain variables to the dat file.  I was wondering if there are any other ways to output data during the execution of a job.  Is it possible to print/plot variables, for example using Matlab (maybe even realtime)?

Also, has anyone experience in accessing the fill files (e.g converting them to ASCII and then use Matlab to look at data?).

Thanks,

Andreas

Hi,

Is anyone aware of a pressure-overcosure function for (nearly) incompressible materials.

 I am aware of functions for PE and articular cartilage but they do not work with v=0.5.   I have been trying to find similar functions for elastomers, but can't seem to find anything.

 I am grateful for any input.

 Andreas

Hi,

 I am trying to implement (in Abaqus) the elasticity tensor using a numerical approach.  I have come across a paper by C.Miehe (Numerical computation of algorithmic (consistent) tangent moduli in large-strain computational inelasticity, 1996).

There are a few things I don't quite understand.  

Hi,

 if I have a material model defined in cauchy stress then I use test data with true stress (calculated from nominal stress: sigma_true=sigma_nom(1+epsilon_nom).

If I wanted to use nominal stress data, which stress tensor would I have to use to define my material model? First or second Piola Kirchhoff?

 Andreas

Hi,

 I have cyclic uniaxial compression data of a PU.  When I look at nominal stress vs nominal strain then the relation is clearly nonlinear (increasing stiffnes with increasing  strain).  When I convert to true stress vs true strain I still have a nonlinear relation, however, not as strong and the stiffness decreases with increasing strain.
When I look at true stress vs stretch, however, the relation seems to be almost (I'm only talking about the first loading cycle) linear. Nominal stress vs stretch is still nonlinear.