Nonlinear material model for Delrin

[rgm1960]

Hello,
Does any one have any info on nonlinear material models for Delrin. I am doing a part evaluation study in ANSYS. Preliminary results from a static analysis using a linear elastic model shows that the predicted max stress exceeds the yield stress under a given load condition. Thanks for any information/pointers you may be able to share.
Regards,
RGM

[Jorgen]

Hello RGM,

The best choice for material model for Delrin will depend on the specifics of the loading and the accuracy that you need in the results. If you are past yielding then a linear elastic material model is not going to be accurate.

To decide what model is most appropriate, you need to know roughly how much past yield you are. If the component is just slightly past yield, then you can perhaps get away with a linear viscoelastic model.

If the strains are larger than that you can use an elastic-plastic material model (i.e. metal plasticity model). It is with some hesitation that I give this recommendation, since it is known that metal plasticity models can give inaccurate results in multiaxial loading situations.

Finally, if you want/need more accurate results then you can use an advanced material model specifically developed for thermoplastics. These models are available as external user material subroutines, see the user material section (http://www.polymerfem.com/modules.php?name=User_Subroutines) of this web site.

-Jorgen