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cabellos

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*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?