S.E. (Mechanical) (First Semester) EXAMINATION, 2012 METALLURGY (Mechanical and Mechanical S/W) (2008 PATTERN) Time : Three Hours Maximum Marks : 100

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1 Total No. of Questions 12] [Total No. of Printed Pages 7 Seat No. [4162]-112 S.E. (Mechanical) (First Semester) EXAMINATION, 2012 METALLURGY (Mechanical and Mechanical S/W) (2008 PATTERN) Time : Three Hours Maximum Marks : 100 N.B. : (ii) (iii) (iv) (v) Answer any three questions from each Section. Answers to the two Sections should be written in separate answer-books. Neat diagrams must be drawn wherever necessary. Figures to the right indicate full marks. Assume suitable data, if required. SECTION I Unit I 1. (a) What are the various point defects in a crystal? What is the effect of these defects on the property of material? [6] Define and explain coldworking of metals. Why is annealing followed by coldworking? [6] (c) Derive an expression for critical resolved shear stress of a single crystal. Calculate resolved shear stress of a single crystal if applied tensile stress is 25 kg/mm 2 and slip plane is oriented 60 to tensile axis. [6] P.T.O.

2 2. (a) Explain phenomenon of strain hardening on the basis of theory of dislocation. [6] Represent the following planes and directions in cubic system : [6] 221 (ii) 210 (iii) 110 (c) Explain the following in brief (any two) : [6] Recrystallisation (ii) Polygonisation (iii) Dislocation. Unit II 3. (a) Tensile test was conducted on a steel specimen of diameter 12 mm and gauge length 60 mm. The load at upper and lower yield point are 4800 kg and 4500 kg respectively. The maximum and fracture load are 7800 kg and 5000 kg respectively. Gauge length 75 mm and gauge dia. 8 mm at the time of fracture. Calculate : Upper and lower yield stress (ii) UTS (iii) % elongation. [6] [4162]-112 2

3 What is fatigue? Explain factors affecting fatigue life. Draw S.N. curve showing all details. [6] (c) Differentiate between Charpy and Izod Impact Test. [4] 4. (a) Define Engineering stress-strain and True stress-strain. Derive relationship between Engineering stress-strain and True stressstrain. [6] Find true stress-strain and engineering stress-strain of a low carbon steel rod if load applied to specimen is 4000 N, initial diameter 0.30 cm and diameter of specimen under load of 4000 N is 0.27 cm. [6] (c) Which NDT test will you recommend for testing of the following : Sorting of steel components of identical shape and size from mixed lot. (ii) Surface cracks in steel bar. (iii) Subsurface cracks in a 8 cylinder crankshaft. (iv) Slag inclusion in a welded joint. [4] [4162] P.T.O.

4 Unit III 5. (a) Write short notes on (any three) : [12] Classification of steels (ii) Specification of steels (iii) Stainless steels (iv) Tool steels. Which steel would you select for : [4] Gear (ii) Wrist watch (iii) Crankshaft (iv) Ball bearing? 6. (a) Draw Fe-Fe 3 C diagram showing all the details. Explain along with reactions, various phases and temperatures. [10] Draw and label microstructures of the following plain carbon steels : [6] Hypoeutectoid (ii) Eutectoid (iii) Hypereutectoid. [4162]-112 4

5 SECTION II Unit IV 7. (a) Represent martempering, austempering, petenting and ausforming with respect to TTT diagrams. State the transformation products of each process. [6] Explain transformation products of Austenite. [6] (c) What is hardenability? Explain any one method of evaluation and discuss factors affecting hardenability. [6] 8. (a) State true or false and justify (any two) : [6] Hypereutectoid steels are hardened above Acm temperature. (ii) Hardness increases during tempering (iii) Annealed steel shows more hardness than normalised steels. Explain flame hardening and induction hardening. Differentiate them with respect to other case hardening processes. [6] (c) Write short notes on any two : [6] Quench Cracks (ii) Secondary Hardness (iii) Carbonitriding. [4162] P.T.O.

6 Unit V 9. (a) Explain the following characteristics of metal powder : [6] Particle size and shape distribution (ii) Flow rate (iii) Apparent density. What is a requirement for self-lubricated bearing? Explain working and steps involved in manufacturing of those bearings. [6] (c) Explain merits and demerits of powder metallurgical process. [4] 10. (a) Give composition, properties and application of the following metals (any three) : [6] Gun metal (ii) Muntz metal (iii) LM6 (iv) Babbits alloy. Explain the factors affecting microstructures of cast iron. [6] (c) Draw the phase diagram of Cu-Zn alloy system, showing all details. [4] Unit VI 11. (a) Explain properties and application of the following fibers : [6] Aramid (ii) Alumina (iii) Glass. [4162]-112 6

7 Explain characteristics of a good composite material. [4] (c) Write a short note on Shape Memory Alloy. [4] (d) State application of biomedical material. [2] 12. Write short notes on (any four) : [16] Fiber reinforced composites (ii) Advanced ceramics (iii) Structural composites (iv) Refractory metals and alloys (v) Cryogenic materials. [4162] P.T.O.