fatigue calculation for thermoplastic materials

[marco]

Hi to everybody,
does anybody know to which theory one should refers for any endurance analysis for a plastic component? I want to perform FEM analysis on a component made of HDPE reinforced with 15%CaCo3 and wondering which admittable fatigue sigma should I use for the analysis.
Thanks alot.
Marco.

[Jorgen]

The fatigue behavior of thermoplastics depends on many variables and it is not easy to say what "fatigue stress limit" you should use. The fatigue strength (and therefore also the lifetime) will depend on the specifics of your HDPE material, and the environment the part is exposed to (temperature, UV radiation, load frequency, etc).

To get good fatigue predictions it is often necessary to perform careful fatigue tests.

- Jorgen