The next diagram shows what each line of a Goodman chart is. In this case, the load line does not start from the origin as shown, but from the preload on the mean stress axis. This next diagram shows the Goodman chart for this case. Torsion 360MPa 3. For the mean stress axis, the maximum principal stress for pure shear is equal to the shear stress.
Lateral forces act in a constant direction.
Hence they lead to oscillating bending stresses in the shaft. The torsion leads to a steady mean stress. K f 60 MPa. The endurance limit can be estimated in 2 ways. Either as 0.5 S u or as 1.73 Bhn.