$($b$)$ A shaft with two supports is loaded in

such a way that the axial thrust on

each bearing is $500$ N and the radial

thrust is $2000$ N and $1000$ N

$F_a=500N$

$F_a=500N$

$F_r=2000N,F_r=1000N$

respectively at left$-$ and right$-$hand bearing. The shaft rotates at $1440$ rpm $.$ The

bearing is to be selected based on $3$ hours per day for $10$ years. The shaft diameter

is $40$ mm but may be reduced if the situation permits considering low moment.

Select the suitable bearings. $[5$ Marks$].$

Problem $4.[10$ Marks$]$

$($a$)$ A solid shaft of diameter $D=50mm$

rotates and carries the minor shock

loading as shown in figure. Calculate

the fatigue safety factor $n$ and

yielding factor of safety $n_y$ for the

shaft. Given: $D=75mm,S_y=550$MPa,

$S_u=660$MPa. The torque fluctuates

$5\%$ each way from the mean value,

and the shaft is to be machined from

unnotched steel. $[5$ Marks$]$