Important Question ESE Mechanical Engineering
1. A reaction-bonded silicon nitride ceramic has a strength of 300 MPa and a fracture toughness of . With in thefracture toughness equation, what is the largest size of internal crack that this material can withstand without fracturing?
(a) 91.6
(b) 82.3
(c) 74.6
(d) 45.8
Ans. (d)
2. The modulus of elasticity of E-glass is 72 GPa and that of epoxy resin is 3 GPa. The modulus of elasticity (to the nearest unit magnitude) for a composite material consisting of 60% by volume of continuous E-glass fibre and 40% epoxy resin for the matrix, when stressed under isostress conditions, is
(a) 4 GPa
(b) 5 GPa
(c) 6 GPa
(d) 7 GPa
Ans. (d)
3. In developing abrasive ceramics which are used to wear, grind or cut away other materials which are (necessarily) softer, they should have, besides wear resistance,
1. a high degree of toughness
2. a low degree of toughness
3. refractoriness
Which of the above is/are correct?
(a) 1 only
(b) 2 only
(c) 1 and 3
(d) 2 and 3
Ans. (c)
4. Consider the following in case of high-energy forming processes :
1. The evacuation between die and blank in explosive forming is done by a vacuum pump.
2. The pressure waves produced in water in explosive forming deform the blank to the die shape.
3. The electrohydraulic forming makes use of discharge of large amount of electrical energy used in a capacitor blank.
4. In Petroforge, the piston is moved by combustion of fuel moving at the rate of 150-200 m/s.
Which of the above are correct?
(a) 1, 2, 3 and 4
(b) 1, 2 and 3 only
(c) 3 and 4 only
(d) 1, 2 and 4 only
Ans. (a)
5. In abrasive jet machining process, the main mechanism of material removal takes place due to
(a) electrochemical action
(b) mechanical impact
(c) fatigue failure of the material
(d) sparking on impact
Ans. (b)
6.Consider that the following materials are usable for manufacturing dies, moulds in investment casting process for the purpose of large-scale production :
1. Aluminum alloy
2. Magnesium alloy
3. Brass
4. Low-carbon steel
Which of the above are correctly usable?
(a) 1, 2 and 3 only
(b) 1, 2 and 4 only
(c) 3 and 4 only
(d) 1, 2, 3 and 4
Ans. (c)
7. The occurrence of casting defect ‘rat tail’ is possible because of
1. soft ramming of sand
2. continuous large flat surface on the mould
3. excessive hardness of the mould
Which of the above reasons are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Ans. (b)
8. Components produced by die casting have finer grain, higher strength and greater hardness at the skin than at the centre due to
(a) decreased wall thickness of die cavity
(b) rapid chilling of molten metal at the die walls
(c) high temperature involved in the process
(d) high tonnage of die casting machines
Ans. (b)
9. A 125 mm long, 10 mm diameter stainless steel rod is being turned to 9 mm diameter, 0.5 mm depth of cut. The spindle rotates at 360 r.p.m. With the tool traversing at an axial speed of 175 mm/min, the metal removal rate is nearly
(a) 2200 mm3/min
(b) 2400 mm3/min
(c) 2600 mm3/min
(d) 2800 mm3/min
Ans. (c)
10. The feed in face milling for a width of 70 mm with a cutter of 160 mm diameter, having 10 inserts and rotating at 360 r.p.m., with a feed rate of 0.5 m/min, is nearly
(a) 0.21 mm/tooth
(b) 0.18 mm/tooth
(c) 0.14 mm/tooth
(d) 0.11 mm/tooth
Ans. (c)
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