orthotropic material

[Ale85]

[highlight #000000][/highlight]
Hy!
I'm using Msc.Patran (Marc solver) to model a CFRP-tape spring. I use a 2D-orthotropic material to model CFRP, but this message appears in .out file:

**** note ****
can not find the following flow-data file
in job directory or in the material library:
C:\MSC.Software\MSC_Nastran\20121\msc20121\marc\AF_flowmat\T300.mat
This is ok if no separate flow-data file is required.
Otherwise please provide the data file or result
will be wrong.
The analysis doesn't converge.. does anyone know why?
Thanks!!!
Ale

 

[hezhj2000]

I don't think that message matters for your problem. You will probably see this message even if your simulation converges. It is really hard to tell what is the problem as there are many factors causing convergence problems. Have you tried adaptive time stepping, and making smaller initial time step?

 

[Ale85]

I tried all available methods: fixed, arc length method, adaptive..
If I use the Auricchio's model for SMAs, the analysis converges. If I use 2d-orthotropic or isotropic models, the analysis doesn't converge (exit number 2004 with the message:

The determinant of the stiffness matrix becomes zero or
negative when indicated node has been reached during the
Gaussian elimination phase of the solution process. This
means that the stiffness matrix is non-positive definite.
If this happens at the start of the analysis, the condition
is usually caused by the existence of rigid body modes. It
may also be caused by incorrect material properties (e.g.
Poisson's ratio greater than 0.5; note that such situations
may arise through temperature dependence of properties). In
nonlinear cases, the structure may have buckled or reached a
plastic limit load. In rubber analysis, it may also be due
to the strain state being in a region where the input data
for the strain energy function is invalid. In contact
analysis with friction, lack of normal forces may result in
friction being absent. If desired, the program may be forced
to continue by use of the parameter PRINT or the model or
history definition option CONTROL. Either one of these
procedures may be used for restart. Whenever a non-positive
definite situation occurs one must exercise caution, as the
resultant numerical solution may be infeasible.)

I don't think it's a boundary condition problem.. the same model with SMA model converges.
I don't know how input the right data for 2d-orthotropic material.