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Thursday, 13 October 2016

Material Science and Engineering- Model question paper for B.E/B.Tech Mechanical Engineering

1(a) You would like to design an aircraft that can be flown by human power nonstop for a distance of 30 km. What types of material properties would you recommend? What materials might be appropriate? (06 Marks)
(b) Explain why modulus of elasticity of simple thermoplastic polymers, such as polyethylene and polystyrene, is expected to be very low compared with that of metals and ceramics? (04 Marks)
(c) What is polymorphism? What are the different polymorphs of carbon? (06 Marks)
(d) What are Miller indices? Sketch (110) and (221) planes in a cubic lattice. (04 Marks)
2(a) Explain the term strain hardening. (04 Marks)
(b) Amorphous PET is more permeable to CO2 than PET that contains micro-crystallites. Explain why? (06 Marks)
(c) Explain Fick’s first law of diffusion. (06 Marks)
(d) A Niobium alloy is produced by introducing tungsten substitutional atoms in the BCC structure; eventually an alloy is produced that has a lattice parameter 0.32554 nm and a density of 11.95 g/cm3. Calculate the fraction of the atoms in the alloy that are tungsten. (04 Marks)
3(a) How is tensile toughness defined in relation to the true stress-strain diagram? How is tensile toughness related to impact toughness? (06 Marks)
(b) FCC metals are often recommended for use at low temperatures, particularly when any sudden loading of the part is expected. Explain why. (04 Marks)
(c) Write down the formulas for calculating the stress and strain for a sample subjected to a tensile test. Assume the sample shows necking. (06 Marks)
(d) When a 3000 kg load is applied to a 10 mm diameter ball in a Brinell test of a steel, an indentation of 3.1 mm is produced. Estimate the tensile strength of the steel. (04 Marks)
4(a) What is the difference between failure of a material by creep and that by stress rupture? (06 Marks)
(b) The amount of plastic deformation that can be performed during hot working is almost unlimited.  Justify this statement. (04 Marks)
(c) Metals like Magnesium cannot be effectively strengthened using cold working. Explain why. (06 Marks)
(d) A polymer that contains internal flaws 1 mm in length fails at a stress of 25 MPa. Determine the plane strain fracture toughness of the polymer. Assume that f =1. (04 Marks)
5(a) What is the difference between fusion welding, brazing and soldering? (06 Marks)
(b)What is ABS copolymer? State some of the applications of this material. (04 Marks)
(c) Briefly state the Hume-Rothery rules and explain the rationale. (06 Marks)
(d) A 10 cm cube of a liquid metal is allowed to solidify. A spherical shrinkage cavity with a diameter of 3.725 cm is observed in the solid casting. Determine the percent volume change that occurs during solidification. (04 Marks)
6(a) Why does the martensite phase not appear on the Fe-Fe 3C phase diagram? (04 Marks)
(b) What is a supersaturated solution? How do we obtain supersaturated solutions during precipitation hardening? Why is the formation of a supersaturated solution necessary? (06 Marks)
(c) Design a corrosion-resistant steel to use for a pump that transports liquid Helium at 4 K in a superconducting magnet. (06 Marks)
(d) A 1030 steel is given an improper quench and temper heat treatment, producing a final structure composed of 60% martensite and 40% ferrite. Estimate the carbon content of the martensite and the austenitizing temperature that was used. What austenitizing temperature would you recommend? (04 Marks)
7(a) Design a nickel-titanium alloy that will produce 60 volume percent Ni3Ti precipitate in a pure nickel matrix. (06 Marks)
(b) What are linear and branched polymers? Can thermoplastics be branched? (06 Marks)
(c) Explain the terms crazing and blushing. (04 Marks)
(d) Calculate the degree of polymerization if 6,6 nylon has a molecular weight of 120,000 g/mol. (04 Marks)
8(a) Draw and explain a typical heat-treatment profile encountered in processing of glass-ceramics. (06 Marks)
(b) Can ceramic materials show superplastic behaviour or are they always brittle? Explain. (04 Marks)
(c) Explain briefly in what sporting equipment composite materials are used? What is the main reason why composites are used in these applications? (06 Marks)
(d) A 0.01 cm thick sheet of a polymer with a modulus of elasticity 4800 MPa is sandwiched between two 4 mm thick sheets of glass with a modulus of elasticity of 83000 MPa. Calculate the modulus of elasticity

of the composite parallel and perpendicular to the sheets. (04 Marks)

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