Machine Design Miscellaneous


  1. Match the rolling element bearings with the most appropriate loading condition
    Bearing-typeLoading condition
    (a) Ball bearing (p) Tangential load
    (b) Roller bearing (q) Radial load
    (c) Needle bearing(r) Heavy radial load with impact
    (d) Taper roller bearing(s) Light radial load with space limitation
    (t) Heavy radial and axial load
    (u) Fatigue load









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    a – q, b – r, c –s, d – t

    Correct Option: C

    a – q, b – r, c –s, d – t


  1. If the load on a ball bearing is reduced to half, the life of the ball bearing will









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    LP3 = C

    ⇒ L1 P13 = L2
    P1
    3
    2

    ⇒ L2 = 8L1

    Correct Option: A

    LP3 = C

    ⇒ L1 P13 = L2
    P1
    3
    2

    ⇒ L2 = 8L1



  1. The expected life of a ball bearing subjected to a load of 9800 N and working at 1000 rpm is 3000 hours. What is the expected life of the same bearing for a similar load of 4900 N and speed of 2000 rpm?









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    L (P)3 = constant

    L1
    =
    P2
    3
    L2P1

    1000 × 60 × 3000
    =
    4900
    3
    2000 × 60 × t29800

    t2 = 12000 hours

    Correct Option: B

    L (P)3 = constant

    L1
    =
    P2
    3
    L2P1

    1000 × 60 × 3000
    =
    4900
    3
    2000 × 60 × t29800

    t2 = 12000 hours


  1. A bolted Joint is shown below. The maximum shear stress, in MPa, in the bolts at A and B, respectively are










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    FA = FB = FC =
    10
    kN
    3

    FA =
    P.e.r
    =
    10 × 103 × 150 × 40
    rA² + rB² + rC²40² + 0² + 40²

    F'A = 18.75 kN = F'C
    Shear load at A and C
    FR = √(FA)² + (F'A = √(3.33)² + (18.75)²
    FR = 19.04 KN
    τmax =
    19.04 × 103
    (π / 4) × 102

    ( τmax )A,C = 242.5 MPa
    ( τmax )B = 42.44 MPa

    Correct Option: A

    FA = FB = FC =
    10
    kN
    3

    FA =
    P.e.r
    =
    10 × 103 × 150 × 40
    rA² + rB² + rC²40² + 0² + 40²

    F'A = 18.75 kN = F'C
    Shear load at A and C
    FR = √(FA)² + (F'A = √(3.33)² + (18.75)²
    FR = 19.04 KN
    τmax =
    19.04 × 103
    (π / 4) × 102

    ( τmax )A,C = 242.5 MPa
    ( τmax )B = 42.44 MPa



  1. In a bolted Joint two smooth members are connected with an axial tightening force of 2200 N. If the bolt used has metric threads of 4 mm pitch, the torque required for achieving the tightening force is










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    Tightening force = 2200 N
    Pitch = 4 mm = 0.004 m

    Torque = Tightening force ×
    0.004
    = 1.4 N-m

    Correct Option: C

    Tightening force = 2200 N
    Pitch = 4 mm = 0.004 m

    Torque = Tightening force ×
    0.004
    = 1.4 N-m