what's the failure density function of spring?

[cherry_cai]

one unit was failed because of a component spring ruptured during testing, so I had a reliability test about the spring, 10 samples,without accelerations
now I've tested for 240 hours (the spring's required life is 100 hours according the products' life), no failure found, and I must derminate the test limited by the time, but It's a litttle difficult to get the related reliability plot because of no failure,and I don't know what the failure density function of spring regularly is, if I get it, I will take it easy.

[Pantelis]

Its fairly safe to assume an exponential distribution in this case. You can compute this without failures.

[cherry_cai]

Its fairly safe to assume an exponential distribution in this case. You can compute this without failures.

thanks!
And another question, the arrhenius equoation can be used in this case if I make the testing under high temperature?

[Pantelis]

Not really... The original equation was for electromigration which I am fairly certain has nothing to do with your spring. You may want to look more to a power model, however you need to first understand the failure mechanism and what you are accelerating, before you start looking at models.