Andhra University 2007 B.E material science and engineering - exam paper

II Year B.E./B.Tech Degree exam

MATERIAL SCIENCE & ENGINEERING

(Chemical Engineering)

Time: three hours Max.Marks: 75

ques. one is compulsory

ans any 4 from ques. two to 8

All ques. carry equal marks

1. ans the following: (5 x three = 15)

a) discuss DHCrystal and Lattice DH . What do they signify in

bonding?

b) What is configurational entropy? How would you

estimate it?

c) elaborate slip systems? provide slip planes and slip systems

of HCP and FCC structures.

d) discuss the mechanism of fatigue failure of materials.

e) Show the heat treatment cycles for Quenching and

Annealing.

2. a) find and expression for the Bond Energy of A X

kind of crystal in which the anion and catino both are

monovalent.

b) 1st 3 lines from powder trend of a Cubic Crystal

have the subsequent S values, 2.495c, 4.09cm, 4.805cm.

On stretching the cassette film the distance ranging from

the entrance and exit slits of the film is 180mm.

Molybdenum of Ka radiation is used to find the

trend and the Wave length of the radiation is 0.710 A.

Determine the structure and the lattice parameter of

the material.

19

3. a) Derive Bragg’s legal regulations of X-ray diffraction. Show that

for any order of reflection n = 1. Briefly analyze the

data found in X-ray diffraction technique using the

metal specimen in the form of powder.

b) Titanium has HCP structure beneath 8800C with a =

2.9650A and c/a ratio of 1.584. If the atomic weight of

titanium is 47.9 g/g atom compute the density of

Titanium. If Titanium reverts to BCC at a temp above

8800C (a = 3.32 A0), compute the change in the Density

during such transformation from HCP to BCC.

4. a) elaborate line defects? With the help of a neat sketch

draw edge dislocation. Show the Burgers circuit and

Burgers vector in the diagram. List the characteristics

of an edge dislocation. discuss the motion of an Edge

dislocation under the influence of Shear stress.

b) An FCC crystal of Aluminium is stressed in [101]

direction, under a stress of 4.24 MN/m2 in tension. On

which of the subsequent systems does slip occur and what

is Critical Resolved shear Stress? The planes and

directions are :

(111) [101] ; (101) [111] ; and (111) [110]

5. a) discuss the Anelastic property (Elastic - After-effect)

of materials with suitable examples. provide the reasons

for Analastic behaviour of materials atomic point of view.

Sketch the Strain Vs time diagram both for loading the

unloading conditions and discuss what is relaxation time?

b) An empirical formula which represents the Strain-

Hardening of behaviour of many engineering materials is:

s1=A(B+et)n

Show that for uniform elongation of such a material

( ) t e = n-B

20

6. a) find Griffith’s criterion for brittle failure. Summarise

with suitable example the characteristics of brittle failure.

Compare this with ductile failure.

b) Enumerate the factors improving the Fatigue resistance

for materials. Using S-N diagram compare the Fatigue

behaviour of Ferrous and non-Ferrous materials.

7. a) Draw Iron-Iron Carbide diagram, tag all the Phase

fields. Indicate (i) Eutectic point (ii) Eutectoid point in

the phase diagram. Write the improper phase

transformation reactions at these points.
b) The phase diagram of a Binary system of A and B has

a 3 phase equilibrium at 2500C with composition

of a , Liquid and b phases equal to 10%, 55% and

95% respectively. Just beneath 2500C obtain the

compositions which proetectic phase is 1.5 times the

Eutectic Mixtures.

8. Write detailed notes on any 3 from the subsequent.3x5=15

a) Electron microscopy for observing the micro-structure

b) Role of dislocation in improving mechanical properties

c) Creep in metals - Creep curve

d) Requirements of use of a material in shipping industry
e) Non-destructive testing of materials used in ship building

industry

f) Heat treatment and its objectives

Earning:   Approval pending.