Machine Design Miscellaneous

Machine Design Miscellaneous

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Machine Design

Machine Design Miscellaneous
  1. For the three bolt system shown in the figure, the bolt material has shear yield strength of 200 MPa. For a factor of safety of 2, the minimum metric specification required for the bolt is








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    σy = 200 MPa
    P = 19 × 10³N

    σ =
    P
    		 ⇒ d = 10.9 mm
    (π/4)(d1)²

    M10

    Correct Option: B

    σy = 200 MPa
    P = 19 × 10³N

    σ =
    P
    		 ⇒ d = 10.9 mm
    (π/4)(d1)²

    M10

  1. A bolt of major diameter 12 mm is required to clamp two steel plates. Cross sectional area of the threaded portion of the bolt is 84.3 mm2. The length of the threaded portion in grip is 30 mm, while the length of the unthreaded portion in grip is 8 mm. Young's modulus of material is 200 GPa. The effective stiffness (in MN/m) of the bolt in the clamped zone is _____.








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    d1 = 12 mm;
    l1 = 8 mm
    A2 = 84.33 mm²

    A1 =
    π
    		(d1)²
    4

    l2 = 30 mm
    K1 =
    A1E1
    l1

    K2 =
    A2E2
    l2

    =
    84.33 × 200
    		 = 562.2
    30

    =
    (π/4)(12)² × 200
    		 = 2827.4
    8

    1
    		 =
    1
    		 +
    1
    KK1K2

    =
    π
    		 × 3000 + 1500 × π
    8

    =
    1
    		 +
    1
    2827.4562.2

    ⇒  K = 468.9 MN/m

    Correct Option: A

    d1 = 12 mm;
    l1 = 8 mm
    A2 = 84.33 mm²

    A1 =
    π
    		(d1)²
    4

    l2 = 30 mm
    K1 =
    A1E1
    l1

    K2 =
    A2E2
    l2

    =
    84.33 × 200
    		 = 562.2
    30

    =
    (π/4)(12)² × 200
    		 = 2827.4
    8

    1
    		 =
    1
    		 +
    1
    KK1K2

    =
    π
    		 × 3000 + 1500 × π
    8

    =
    1
    		 +
    1
    2827.4562.2

    ⇒  K = 468.9 MN/m

  1. In thick film hydrodynamic Journal bearings, the coefficient of friction








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    f ∝
    μN
    P

    Correct Option: C

    f ∝
    μN
    P

  1. To restore stable operating condition in a hydrodynamic Journal bearing, when it encounters higher magnitude of loads








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    For stability
    ZN
    		↑ &Z ↑ &P ↓
    P

    Correct Option: B


    For stability
    ZN
    		↑ &Z ↑ &P ↓
    P

  1. A force of 400 N is applied to the brake drum of 0.5 m diameter in a band brake system as shown in figure, where the wrapping angle is 180°. If the coefficient of friction between the drum and the band is 0.25, the braking torque applied, in Nm is








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    As the drum is rotating in anti clock wise direction, T1 will be right side & T2 will be clock side.

    T1
    		 = eμθ = e0.25 × π = 2.19
    T2

    ⇒  T2 = = 182.375 N
    Braking torque = (T1 – T2 )r
    = 54.4 N – m

    Correct Option: B


    As the drum is rotating in anti clock wise direction, T1 will be right side & T2 will be clock side.

    T1
    		 = eμθ = e0.25 × π = 2.19
    T2

    ⇒  T2 = = 182.375 N
    Braking torque = (T1 – T2 )r
    = 54.4 N – m