error "complex sound speed reached"
Hello, I am researching a method of evaluating 3D printed parts with regards to different properties depending on layer orientation. I am recreating an experiment - bending of a beam with 2 supports, one on each end and a load probe in the middle. So far I have completed both explicit and implicit analysis using MAT_024 model and the results correlate with experiment, but for the next stage I am testing various material models that enable to define material axis and view strains in layer orientations, basically using materials for solid elements with AOPT option. So far I made an implicit analysis with MAT_002 work and it enables to view directional strains as desired but the results are way off since it is just a linear elastic model.
The most suitable seems to be MAT_040 but I cannot make the explicit work. After a few minutes and two completed d3plots (including the first one with no loading force) it terminates with error "complex sound speed reached in elements xxxxx". All affected elements are near the probe contact area.
Handbook says this about MAT_040: "We do not recommend using this model at this time since it can be unstable especially if the stress-strain curves increase in stiffness with increasing strain." Is it just that the material model is not yet fully developed, or does anyone else have experience with this type of error and what It may be caused by?
I will provide additional info about the analysis if needed.
Thanks in advance.