Materials Science and Manufacturing Engineering Miscellaneous


Materials Science and Manufacturing Engineering Miscellaneous

Materials Science and Manufacturing Engineering

  1. The process of hot extrusion is used to produce









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    Aluminium is ductile at higher temperature.

    Correct Option: A

    Aluminium is ductile at higher temperature.


  1. For wire drawing operation, the work material should essentially be









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    For wire drawing, work material should be ductile in nature.

    Correct Option: A

    For wire drawing, work material should be ductile in nature.



  1. During open die forging process using two flat and parallel dies, a solid steel disc of initial radius (RIN) 200 mm and initial height (HIN) 50 mm attains a height (HFN) of 30 mm and radius of RFN,
    Along the die-disc interfaces,
    (i) The coefficient of friction (μ) is:
    μ = 0.35 [1 + e–RIN/RFN]
    (ii) In the region Rss ≤ r ≤ RFN sllding friction prevails and P = √3 K.e(RIN–r)/HFN and ι = μp,
    sllding friction prevails and
    Where p and ι are the normal and the shear stresses respectively; K is the shear yield strength of steel and r is the radial distance of any point.
    (i) In the region 0 ≤ r ≤ RIN, sticking condition prevails.
    The value of Rss (in mm), where sticking condition changes to sliding friction is









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    At RSS,

    π
    d02 × h0 = πR2FN × h1
    4

    RFN
    Shear stress sticking (k) = Shear stress in sliding (μPss)
    ∴ RSS = RFN -
    h
    In
    1
    3μ

    = 258.2 -
    30
    In
    1
    2 × 0.513 × 0.51

    = 254.55 mm

    Correct Option: B

    At RSS,

    π
    d02 × h0 = πR2FN × h1
    4

    RFN
    Shear stress sticking (k) = Shear stress in sliding (μPss)
    ∴ RSS = RFN -
    h
    In
    1
    3μ

    = 258.2 -
    30
    In
    1
    2 × 0.513 × 0.51

    = 254.55 mm


  1. Hot die steel, used for large solid dies in drop forging, should necessarily have









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    High toughness for hammering action and low thermal conductivity for retaining higher temperature.

    Correct Option: C

    High toughness for hammering action and low thermal conductivity for retaining higher temperature.



  1. By application of tensile force, the cross sectional area of bar P is first reduced by 30% and then by an additional 20%. Another bar Q of the same material is reduced in cross sectional area by 50% in a single step by applying tensile force. After deformation, the true strain in bar P and bar Q will, respectively be









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    True strain

    ε = In
    Ai
    Af

    εT = In
    Ai
    0.8 × 0.7Ai

    εT = In
    1
    0.56

    εT = 0.58
    True strain in single step of 50%
    εT = In
    Ai
    Af

    = In
    Ai
    0.5Ai

    εT = In(2) = 0.693

    Correct Option: B

    True strain

    ε = In
    Ai
    Af

    εT = In
    Ai
    0.8 × 0.7Ai

    εT = In
    1
    0.56

    εT = 0.58
    True strain in single step of 50%
    εT = In
    Ai
    Af

    = In
    Ai
    0.5Ai

    εT = In(2) = 0.693