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GATE 2017-2018 :: GATE Metallurgical

  1. Fracture stress for a brittle material having a crack length of 1 μm is 200 MPa. Fracture stress for the same material having a crack length of 4 μm is
  2. A.
    200 MPa
    B.
    150 MPa
    C.
    100 MPa
    D.
    50 MPa

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  3. The flow stress  of an alloy varies with strain rate  MPa. When the alloy is hot extruded from 10 cm diameter to 5 cm diameter at a speed of 2 cm/s, the flow stress is
  4. A.
    1000 MPa
    B.
    105 MPa
    C.
    150 MPa
    D.
    1050 MPa

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  5. Determine the correctness or otherwise of the following Assertion (a) and Reason (r). 
    AssertionDuring rolling, front tension and (or) back tension are (is) employed to decrease rolling load. 
    Reason : Roll pressure decreases due to lowering of flow stress as a result of front tension/back tension.
  6. A.
    a
    B.
    a
    C.
    a
    D.
    a

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  7. Match the defects listed in Group I with the processes listed in Group II
    Group I                      Group II
    P. Cold shut             1. Rolling
    Q. Earing                  2. Forging
    R. Alligatoring         3. Deep drawing
    S. Shrinkage porosity  4. Fusion welding
  8. A.
    P-2, Q-4, R-1, S-4
    B.
    P-2, Q-4, R-3, S-1
    C.
    P-2, Q-3, R-1, S-4
    D.
    P-4, Q-1, R-2, S-3

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  9. A steel ball (density ρsteel = 7200 kg/m3) is placed in an upward moving liquid Al (density ρAl = 2360 kg/m3, viscosity μAl = 1 * 10“3 Pa.s and Reynolds number = 5 * 105). The force (F) exerted on the steel ball is expressed as 
    F = f π R2(ρAl v2/2)
    where, f is friction factor (=0.2), v is the velocity of liquid Al and R is the radius of steel ball.
    The force exerted on the steel ball is
  10. A.
    8.32 N
    B.
    6.70 N
    C.
    1.67 N
    D.
    0.52 N

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  11. A steel ball (density ρsteel = 7200 kg/m3) is placed in an upward moving liquid Al (density ρAl = 2360 kg/m3, viscosity μAl = 1 * 10“3 Pa.s and Reynolds number = 5 * 105). The force (F) exerted on the steel ball is expressed as 
    F = f π R2(ρAl v2/2)
    where, f is friction factor (=0.2), v is the velocity of liquid Al and R is the radius of steel ball.
    The terminal velocity of a fine spherical steel particle having diameter dp, in μm range, if allowed to fall in a quiescent liquid Al bath, is
  12. A.
    5.2 * 106 dp2
    B.
    2.6 * 106 dp2
    C.
    1.3 * 106 dp2
    D.
    6.6 * 105 dp2

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  13. For the above stress cycle 
    Stress ratio is
  14. A.
    4
    B.
    2
    C.
    -2
    D.
    -4

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  15. For the above stress cycle 
    Amplitude ratio is
  16. A.
    3
    B.
    1/3
    C.
    -1/3
    D.
    -3

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  17. A material with grain size of ASTM No. 6 has a lattice frictional stress 100 MN/m2 and locking parameter (Hall-Petch constant) 0.10 MN/m3/2 
    Grain size of the material is approximately
  18. A.
    45 μm
    B.
    35 μm
    C.
    4.5 μm
    D.
    3.5 μm

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  19. A material with grain size of ASTM No. 6 has a lattice frictional stress 100 MN/m2 and locking parameter (Hall-Petch constant) 0.10 MN/m3/2 
    Yield strength of the material is approximately
  20. A.
    100 MPa
    B.
    115 MPa
    C.
    165 MPa
    D.
    215 MPa

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