A rotating shaft is made of AISI 1020 CD steel (UTS = 470 MPa). If the modified endurance limit (Se) is 195 MPa, what would be the maximum stress [MPa] for the shaft to last up to 150,000 cycles? Assume the fatigue strength at 1000 cycles is 0.79 UTS.

232.715 MPa

Explanation:

A flow diagram showing the graphical illustration on how to solve the question is attached below;

From the diagram:

We can determine the maximum stress [MPa] for the shaft to last up to 150,000 cycles as follows:

- 3 ( y -2.29) = (-0.824 × 0.2797)

-3y + 6.87 = - 0.2304728

6.87 + 0.2304728 = 3 y

7.1004728 = 3y

y =

y = 2.3668

where y = log σ

log σ =  2.3668

σ = 232.715 MPa

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