Concept explainers
Repeat the requirements of Prob. 6-35 with the following loading conditions:
Bending: Fluctuating stress from −40 MPa to 150 MPa
Axial: None
Torsion: Mean stress of 90 MPa, with an alternating stress of 10 percent of the mean stress
6-35 A part is loaded with a combination of bending, axial, and torsion such that the following stresses are created at a particular location:
Bending: Completely reversed, with a maximum stress of 60 MPa
Axial: Constant stress of 20 MPa
Torsion: Repeated load, varying from 0 MPa to 50 MPa
Assume the varying stresses are in phase with each other. The part contains a notch such that Kf.bending = 1.4, Kf.axial = 1.1. and Kf.torsion = 2.0. The material properties are Sy = 300 MPa and Su = 400 MPa. The completely adjusted endurance limit is found to be Se = 200 MPa. Find the factor of safety for fatigue based on infinite life, using the modified Goodman criterion. If the life is not infinite, estimate the number of cycles. Be sure to check for yielding.
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