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1.
A low carbon steel bar of 147 mm diameter with a length of 630 mm is being turned with uncoated carbide insert. The observed tool lives are 24 min and 12 min for cutting velocities of 90 m/min and 120 m/min respectively. The feed and depth of cut are 0.2 mm/rev and 2 mm respectively. Use the unmachined diameter to calculate the cutting velocity.
[1] When tool life is 20 min, the cutting velocity in m/min is [2 marks]
(A) 87
(B) 97
(C) 107
(D) 114[2] Neglect over – travel or approach of the tool. When tool life is 20 min, the machining time in min for a single pass is [2 marks]
(A) 5
(B) 10
(C) 15
(D) 20asked in Mechanical Engineering, 2007
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2.
A quick return mechanism is shown below. The crank OS is driven at 2 rev/s in counter–clockwise direction.
[1] If the quick return ratio is 1:2, then the length of the crank in mm is [2 marks]
(A) 250
(B) 250√3
(C) 500
(D) 500√3[2] The angular speed of PQ in rev/s when the block R attains maximum speed during forward stroke (stroke with slower speed) is [2 marks]
(A) 1/3
(B) 2/3
(C) 2
(D) 3asked in Mechanical Engineering, 2007
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3.
A machine frame shown in the figure below is subjected to a horizontal force of 600 N parallel to z – direction.
[1] The normal and shear stresses in MPa at point P are respectively [2 marks]
(A) 67.9 and 56.6
(B) 56.6and 67.9
(C) 67.9 and 0.0
(D) 0.0and 56.6[2] The maximum principal stress in MPa and the orientation of the corresponding principal plane in degrees are respectively
(A) -32.0 and -29.52
(B) 100.0and 60.48
(C) -32.0and 60.48
(D) 100.0and -29.52asked in Mechanical Engineering, 2007
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4.
Consider steady one-dimensional heat flow in a plate of 20 mm thickness with a uniform heat generation of 80 MW/m3 . The left and right faces are kept at constant temperatures of 160°C and 120°C respectively. The plate has a constant thermal conductivity of 200 W/mK.
[1] The location of maximum temperature within the plate from its left face is [2 marks]
(A) 15 mm
(B) 10mm
(C) 5mm
(D) 0mm[2] The maximum temperature within the plate in °C is [2 marks]
(A) 160
(B) 165
(C) 200
(D) 250asked in Mechanical Engineering, 2007
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5.
Consider a steady incompressible flow through a channel as shown below.
The velocity profile is uniform with a value of at the inlet section A. The velocity profile at section B downstream is
[1] The ratio Vm/uo is [2marks]
(A)1/[1-2(δ/H)]
(B) 1
(C) 1/[1-(δ/H)]
(D) 1/[1+(δ/H)][2] The ratio (PA -PB)/(ρuo2/2) (where and are the pressures at section A and B, respectively, and ρ is the density of the fluid) is [2 marks]
(A) 1/[1-(δ/H)]2 - 1
(B) 1/[1-(δ/H)]2
(C) 1/[1-(2δ/H)2] - 1
(D) 1/[1+(δ/H)]
asked in Mechanical Engineering, 2007
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6.
A thermodynamic cycle with an ideal gas as working fluid is shown below.
[1] The above cycle is represented on T-S plane by [2 marks]
[2] If the specific heats of the working fluid are constant and the value of specific heat ratio γ is 1.4, the thermal efficiency (%) of the cycle is [2 marks]
(A) 21
(B) 40.9
(C) 42.6
(D) 59.7asked in Mechanical Engineering, 2007
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