(1) Bearing Design (13 points)

As shown below, the rotational shaft is supported by a pair of bearing 7207AC. Given the radial force on the shaft F_{R} = 2050N the axial force on the shaft F_{A} = 700N and the rotational speed of the shaft n = 1200r / m * in The factor of impact load f_{d} = 1.15 under normal temperature. Its basic dynamic load rating C = 22000N Try to find out the life of the bearing.

The additional axial force F_{s} = 0.68F_{r} e = 0.68 If F/F?e, X = 1 , Y = 0 If F/Fe, X = 0.41 , Y = 0.87 .