Creep analysis of plastic material

[scandroglio]

Hello to all forum,
I'm starting to ask a question a bout creep simulation and analysis of plastic.
To simulate a creep behaviur of plastic material as delrin, Nylon...after 800h of creep I use the law epsilon=A*sigmaexpn*t.
With this kind of law I don't consider primary zone of creep but only secondary zone of creep.
I made this kind of hypotesis because I think that the time of 800h is bigger that the time where finish primary creep zone so the strain of secondary zone is very very bigger to strain of primary zone and can remove it.
This hypotesis is "too strong" or can considered it good?

Regards
Jacopo

 

[btrueblood]

It is the usual assumption made, since the resulting analysis is fairly straightforward, and prediction/analysis of primary creep is relatively difficult. You will need test data to show the temperature and stress limits within which your assumption is valid.