Project ForgeMachine Design
Design Against Static Load
GATE 2010
Hard
A lightly loaded full journal bearing has journal diameter of 50 mm, bush bore of 50.05 mm and bush length of 20 mm. If rotational speed of journal is 1200 rpm and average viscosity of liquid lubricant is 0.03 Pa·s, the power loss (in W) will be
- 37
- B74
- C118
- D237
Explanation
Radial clearance c=(50.05-50)/2=0.025mm=0.000025m, r=0.025m, L=0.02m, ω=2πN/60=125.66 rad/s. Shear stress at journal surface τ=μ(rω)/c. Friction torque T=τ·(2πrL)·r=2πμωr³L/c=2π(0.03)(125.66)(0.025)³(0.02)/0.000025≈0.2961 N·m. Power=Tω=0.2961×125.66≈37.2 W.
Source: GATE ME 2010 (2010)
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