PEEK analysis with Ansys workbench.

[Calc]

Hi, I'm a mechanical engineer who unfortunately came across some peek that needs to be investigated :tongue:

Basically, I have a pipe section of peek that needs to hold a certain amount of pressure.

Could you guys point me to a place to get started with this? (I'm totally blank)

Thank you!

[Jorgen]

Hmm, perhaps you can use Ansys ;)

Can you explain more about your main challenges?

- Jorgen

[Calc]

I don't have much experience with ansys, but I would sure give it a try.

The main challenge making the peek pipe section strong enough to withstand a pressure of 15000psi. The real problem is a bit more complicated, but I think it's good to start with something basic.

What I have done now is to specify a ketron 1000 peek material in ansys and run a simple analysis with pressure. I get values that are a bit over the yield strength of the material.

Since I don't know much about peek, or thermoplastics in general, I'm wondering if a simple analysis as I have described is sufficient?

Thank you

[Jorgen]

For SI users: 15 ksi = 103 MPa, which is a high pressure indeed. If you just want a estimate of the plastic strains then you can use a simple elastic-plastic material model. I would not simply use a linear elastic material model since the stress is above yield.

-Jorgen

[Calc]

What I know is that the tensile strength falls rather drastically with temperature.
The Stress-Strain curve for peek flattens out after yield (from victrex).

Can I use Multilinear Isotropic Hardening to define the stress vs. plastic strain?
I'm not sure how to define tensile stress as a function of temperature though, any thoughts?

Thank you for your time!

[Jorgen]

Yes, you can approximate the response of PEEK as a Multilinear Isotropic Hardening Material. Note, however, that metal plasticity model typically give very poor predictions in duing unloading.

Most FE programs allow you to specify the material parameters as a function of temperature.

Also, there are more accurate material models (http://usermaterial.polymerfem.com/) for PEEK than a simple isotropic hardening plasticity model.

-Jorgen