Question

determine the intensity of shear of an oil having viscosity 1.2 poise and is used for lubrication in the clearance between a 10cm diameter shaft and its journal bearing. the clearance is 1.0 mm and shaft rotates at 200 r.p.m

Answer 1

The intensity of shear oil is 125.66 n / m^2

Explanation:

• Diameter of shaft D=10cm=0.1mD=10cm=0.1m
• Distance between shaft and journal bearing dy = 1.0mm=10 −3m
• Speed of shaft N=200 r.p.m

Solution:

Tangential speed "u" = πDN / 60​  

                              = π x 0.1m x 200 r.p.m./ 60

​Tangential speed = π/3m/s

Now Change of velocity between shaft and bearing

du = u − 0 =  π/ 3m/s

Mathematical derivation;

τ = μ  du / dy = 0.12 Ns/m^2 x  π / 3 / 10^-3  

τ  = 40 π N / m^2 = 125.66 n / m^2