Third Semester B.E. IA Test, 2014
USN
1 P E
M E
PES INSTITUTE OF TECHNOLOGY BANGALORE (South Campus)
(Hosur Road, 1KM before Electronic City, Bangalore-560 100)
Department of Mechanical Engineering
Date: 26-08-2014
Subject & code: Material Science and Metallurgy(10ME32A)
Name of faculty: Mr.Manjunath G D
Max Marks: 50
Time: 90 Mins.
Solution for 1st IA test
1. Define unit cell? Differentiate between Crystalline and amorphous solids.
(10 Marks)
Solution: A unit cell is the smallest repeatable unit in a Crystalline solid. In other words
every Unit Cell in a Crystalline solid consist of a group of atoms arranged in definite order.
Crystalline Solids
1.The basic structural unit is crystal.
2.Atoms are orderly arranged
3.Density of Crystalline solids are high.
4.structures are stable
5.Materials are stronger
6.Eg: Metals,alloys,Nacl,KCl,Diamond etc
Amorphous Solids
The basic structural unit is molecule.
Atoms are randomly arranged
Density of amorphous solids are low
Structures are unstable
Materials less stronger
Eg: Glass,Polymers,Rubber,Plastics etc
2. What is Atomic Packing Factor? Derive an expression for APF of HCP structure (c=1.633a)
(10 Marks)
Solution: APF: It is the ratio of the volume of atoms contained in each unit cell to the volume of
the unit cell itself.
APF= Volume of atoms
Volume of unit cell
For derivation Ref: MSM by K.R. PHANEESH, Page no. 10 & 11.
3. List different types of crystal Crystal imperfections and explain point imperfections in detail.
(10 Marks)
Solution: a) point imperfections
b) line imperfections
c) volume imperfections
d) surface imperfections.
Point imperfections are vacancy, interstitialcy, substitutional defects, electronics defects.
For details Ref: MSM by K.R. PHANEESH, Page no. 18 & 19.
Department of Mech Engg
PESIT, Bangalore (South Campus)
4. What is atomic diffusion ? Explain the factors which effecting atomic diffusion?
(10 Marks)
Solution: The migration of atoms from their original lattice sites in crystal structure to other sites
is known as Atomic diffusion.
Factors affecting atomic diffusion are Temperature, Crystal Structure, APF, Grain size, Grain
Boundaries, Atomic Size, Concentration gradient. Etc.
For details of factors Ref: MSM by K.R. PHANEESH, Page no. 28.
5. State and Explain Fick’s I Law and Fick’s II Law of Diffusion.
(10 Marks)
Ficks I Law statement: It state that , the flux of atoms J moving across a unit surface area in unit
time is proportional to the Concentration gradient.
Ficks II Law state that,”the rate of compositional change is equal to the diffusivity times the rate
of change of the concentration gradient”.
For details and Equation Ref: MSM by K.R. PHANEESH, Page no. 25,26 & 27.
6. The Diffusivity of copper atoms in the FCC copper lattice is 8.0 x 10-21 m2/s at 4000C and 6.0 X10-15
m2/s at 8000C. Calculate the activation energy in joules per mole for the different copper atoms in the
FCC copper lattice in this temperature range. Data R=8.314 J/mol-k
(10 Marks)
Ans: Q=203158 J/mol or Q=203.158KJ/mol
For details Ref: MSM by K.R. PHANEESH, Page no. 30 & 31.
7. (A) Draw the stress strain curve for Mild Steel, Cast iron, Aluminum and Rubber materials.
(B) Define Stiffness, Hardness, Resilience, ductility and malleability of Materials.
(10 Marks)
Solution: For details of Stress strain curve Ref: MSM by K.R. PHANEESH, Page no. 38
& 39.
Stiffness: Stiffness is defined as the resistance offered by the material to elastic deformation.
Resilience is the ability of the material to absorb energy when it is loaded elastically and give
back the same energy when the load is removed.
Hardness: Hardness is commonly defined as the resistance to scratch, impression or indentation.
Ductility: is the ability of the material to undergo plastic deformation under tensile load.
Malleability is the ability of the material to undergo plastic deformation under compressive load.
Department of Mech Engg
PESIT, Bangalore (South Campus)