2. A shaft assembly made from 4340 steel is loaded as shown with P cycling from zero to Pmax. A 12 in. diameter disk is attached to one end of the shaft; the other end is fixed to a rigid structure. Near the rigid structure, a mild fillet at the shaft step up results in a stress concentration factor K₁ = 1.2 for the stress generated by bending; the shear stress generated by the torsion loading is not significantly affected by the stress concentration. 10 in. 6 in. 2 in. dia Properties and fatigue parameters for 4340 steel (with common aircraft heat treatment): E = 30 × 10³ ksi, σ = 160 ksi, σ = 170 ksi, σ,' = 255 ksi, b = −0.0977 (a) Determine the largest value of Pmax that may be applied to the disk for a fatigue life of 10,000 cycles for the shaft. Use the Sines' criterion as described in the SAE Fatigue Design Handbook, 3rd Ed. (excerpt posted in Handouts Folder on OneNote).

Fig: 1