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Ex/PG/ME/T/128K/99/2009

MASTEROF MECHANICAL ENGINEERING EXAMINATION, 2009

( 2nd semester )

ADVANCED MANUFACTURING SCIENCE

Time : Three hours Full Marks : 100

Answerany fivequestions

Answer should be brief & to the point.

1. a) Figure - 1 shows a mould along with the riser for casting

a plate 20 cm 5 20 cm 5 5 cm. Determine the area Agsuch that the mould & the riser get filled up within 10 sec.

after the down spruce has been filled.

It should be noted that A3 ? Ag since below the down

spruce a flat gate is attached to the casting.

Neglect the frictional and orifice effects.

[ Turn over

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b) Briefly discuss the arc structures indicating the different

zones in a labelled sketch.

c ) Discuss about Metal- Iner t gas welding . 7+5+8=20

Fig. 1

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b) What are the causes of various casting defects ?

c) Why is diecasting process employed for low melting metals

& alloys ? 12+5+3=20

2. a) Determine the solidification time of the following two iron

castings when both are poured, with no super heats, into

sand at the initial temperature 28oC.

i) A slab-shaped casting 10 cm thick

ii) A sphere 10 cm in diameter.

The data for iron is

f = 1540oC, L = 272 kJ/kg, m = 7850 kg/m3 and for

sand is

C = 1.17 kJ/kg K, K = 0.8655 W/mK, = 1600 kg/m3.

b) Discuss about the solidification of metals and alloys.

c) What is CFR ? Explain it. 10+6+4=20

3. a) In a butt welding process using arc welding, the arc power

is found 2.0 kVA. The process is used to weld two steel

plates, each of 3 m.m. Thickness , as shown in Fig-2.

Determine the maximum possible welding speed. It is

assumed that the metal transfer is of short circuit type and

the arc is on for 85% of the total time. Given

steel = 1.2 5 105 m2/s,Ksteel = 43.6 W/m

oC

b) During an orthogonal machining operation on mild steel,

the results obtained are

t1 = 0.25 mm, t2 = 0

.75 mm, w = 2.5 mm, o0 , =

FC = 950 N, FT = 475N.

i) Determine the co-efficient of friction between the tool

and the chip.

ii) Determine the ultimate shear stress T of the work

material. 10+10=20

6. a) There are two important yield criteria which are used in

practice. Explain these yield criteria and state the basic

differences between the two.

b) Show the relationship between Tensile yield stress and

shear yield stress under these two criteria.

c) What load is required to deform a cube of 80 mm side, if

constrained forces on its sides are both 160 tonnes.

Yield stress of the cube material is 60 tonnes/cm2.

8+6+6=20

7. a) What are the defects in metal forming process ? Discuss.

b) With a neat sketch, describe the cold chamber die-casting

process . 10+10=20

8. a) What are the major defects in butt welds. Give necessary

sketches.

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[ Turn over

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