Repeat Prob. 6–20 but with an alternating torsional stress of 15 kpsi and a steady bending stress of 15 kpsi.
Repeat Prob. 6–20, A bar of steel has the minimum properties Se = 40 kpsi, Sy = 60 kpsi, and Sut = 80 kpsi. The bar is subjected to a steady torsional stress of 15 kpsi and an alternating bending stress of 25 kpsi. Find the factor of safety guarding against a static failure, and either the factor of safety guarding against a fatigue failure or the expected life of the part. For the fatigue analysis use:
(a) Modified Goodman criterion.
(b) Gerber criterion.
(c) ASME-elliptic criterion.