Determine maximum shearing stress in shaft, Mechanical Engineering

Determine maximum shearing stress in shaft: 

A propeller shaft 100 mm in the diameter, is 45 m long, transmits 10 MW at 80 rotation per minute. Determine maximum shearing stress in shaft. Also compute the stress at 20 mm, 40 mm, 60 mm and 80 mm diameters. Demonstrate the stress variation.

Sol.:  

d = 100mm

L = 45m

P = 10MW = 10 × 106  W

N = 80RPM

Τmax = ?

τ20 = ?,  τ 40 = ?,  τ 60 = ?,  τ 80 = ?

By using the relation

P = 2  .N.Tmax/60 watts

10 × 106 = 2  .80.Tmax/60

Tmax = 1193662.073 N                                                                                       ...(i)

For solid shaft    τ = 16Tmax/  d3

τ = 16(1193662.073)/[  (100)3]

τ= 6.079 N/mm2

This is shear stress at outer surface that is;  τ100  = 6.079 N/mm2                                             .......ANS

Now stress is varies linearly along diameter of shaft, the shear stress at inner diameter of

the shaft that is; τ20 =  τ20   × d20/d100  = 6.079 × 20/100 = 1.22 N/mm2

τ100 = 1.22 N/mm2                                                                                                      ......ANS

τ40 =  τ100 × d40/d100  = 6.079 × 40/100 = 2.44 N/mm2

τ40 = 2.44 N/mm2                                                                             .......ANS

τ40 =  τ100 × d60/d100  = 6.079 × 60/100 = 3.66 N/mm2

τ40 = 3.66 N/mm2                                                                              .......ANS

τ40=  τ100 × d80/d100  = 6.079 × 80/100 = 4.88 N/mm2

τ40= 4.88 N/mm2                                                                                .......ANS

Posted Date: 10/27/2012 1:23:42 AM | Location : United States






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