Materials Science and Manufacturing Engineering Miscellaneous

Materials Science and Manufacturing Engineering Miscellaneous

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Materials Science and Manufacturing Engineering

Materials Science and Manufacturing Engineering Miscellaneous
  1. During a TIG welding process, the arc current and arc voltage were 50 A and 60 V, respectively, when the welding speed was 150 mm/min. In another process, the TIG welding is carried out at a welding speed of 120 mm/min at the same arc voltage and heat input to the material so that weld quality remains the same. The welding current (in A) for this process is ___________








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    Total heat input = VIt
    Time t is inversely proportional to weld speed (S)

    ∴ 
    V2I2
    		 =
    V1I1
    S2S1

    ∴  I2 =
    120
    		 × 50
    150

    I2 = 40A

    Correct Option: A

    Total heat input = VIt
    Time t is inversely proportional to weld speed (S)

    ∴ 
    V2I2
    		 =
    V1I1
    S2S1

    ∴  I2 =
    120
    		 × 50
    150

    I2 = 40A

  1. A DC welding power source has a linear voltagecurrent (V-I) characteristic with open circuit voltage of 80 V and a short circuit current of 300 A. For maximum arc power, the current (in Ampere) should be set as______.








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    Constant Voltage characteristics

    150A = vocV −
    vocV
    		I
    1scc

    V = 80 −
    80
    		I
    300

    P = V I
    = 80 −
    80
    		II
    300

    For Maximum Power
    dP
    		 = 0
    dI

    80 – 2 × 0.666 I = 0
    I = 150A

    Correct Option: A

    Constant Voltage characteristics

    150A = vocV −
    vocV
    		I
    1scc

    V = 80 −
    80
    		I
    300

    P = V I
    = 80 −
    80
    		II
    300

    For Maximum Power
    dP
    		 = 0
    dI

    80 – 2 × 0.666 I = 0
    I = 150A

  1. In a linear arc welding process, the heat input per unit length is inversely proportional to








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    Heat Input =
    Voltage × current
    welding speed

    SoHeat Input ∝
    1
    welding speed

    Correct Option: C

    Heat Input =
    Voltage × current
    welding speed

    SoHeat Input ∝
    1
    welding speed

  1. In a DC arc welding operation, the voltage-arc length characteristic was obtained as Varc = 20 + 5l where the arc length l was varied between 5 mm and 7 mm. Here Varc denotes the arc voltage in Volts. The arc current was varied from 400 A to 500 A. Assuming linear power source characteristic, the open circuit voltage and the short circuit current for the welding operation are








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    Var = 20 + 5l
    For l = 5 mm, Varc = 45 V
    For l = 7 mm, Varc = 55V

    V = V0 −
    V0
    		I
    IS

    where Vo is open circuit voltage and IS is short circuit current.
    ∴  45 = V0 −
    V0
    		× 500
    IS

    and   55 = V0 −
    V0
    		× 400
    IS

    By solving, we get
    V0 = 95 Volts
    IS = 950 A

    Correct Option: C

    Var = 20 + 5l
    For l = 5 mm, Varc = 45 V
    For l = 7 mm, Varc = 55V

    V = V0 −
    V0
    		I
    IS

    where Vo is open circuit voltage and IS is short circuit current.
    ∴  45 = V0 −
    V0
    		× 500
    IS

    and   55 = V0 −
    V0
    		× 400
    IS

    By solving, we get
    V0 = 95 Volts
    IS = 950 A

  1. Which one among the following welding processes uses non-consumable electrode?








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    Tungsten Electrode is used to create arc only. Reverse polarity is used to weld Aluminium metal.

    Correct Option: C

    Tungsten Electrode is used to create arc only. Reverse polarity is used to weld Aluminium metal.