# Repeat Prob. 620 but with an alternating torsional stress of 15 kpsi and a steady bending stress

## Question:

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.

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## Shigleys Mechanical Engineering Design

**ISBN:** 978-1121345317

9th edition

**Authors:** Richard G. Budynas, J. Keith Nisbett