Im having a problem with the following question and my understanding of it...(adsbygoogle = window.adsbygoogle || []).push({});

An aluminium alloy obeys the fatigue law S = 895N^-0.12, where S is the stress amplitude and N is the number of cycles. An airdraft componentfabricated from this alloy, undergoes the following stress amplitude history in a typical flight: 1000 cycles where S = 130; 450 cycles where S = 190; and 2 cycles where S = 290. Calculate the number of flights corresponding to the fatigue life of this component?

My method was to use miners law and so the number of flights would be N1(S1/895)^1/0.12 + N2(S2/895)^1/0.12 + N3(S3/895)^1/0.12 = the number of flights but this answer comes out very large at something to the power 16!!

Is this the correct method?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Fatigue question ?

**Physics Forums | Science Articles, Homework Help, Discussion**