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
Prob. 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. If the life is not infinite, estimate the number of cycles. Be sure to check for yielding.
