Julian

Question 1

What is the Lennard-Jones Potential Equation

Answer 1

V(r)=4ε[(σ/r)^12-(σ/r)^6 ]
V is the potential bonding energy in eV
ε the energy required to break the bond
σ distance when bond energy is zero.
r is the distance between atoms

Question 2

Which parts of the lennard jones equation represent repulsive forces

Answer 2

(σ/r)^12

Question 3

Which parts of the lennard jones equation represent attractive forces

Answer 3

(σ/r)^6

Question 4

what is V(r) at r0 and what does it represent

Answer 4

ε, this is the well depth, where atoms like to sit.

Question 5

what is an intensive property and give examples

Answer 5

a property that is INdependent of the mass of the object

such as density, bond energy and viscosity

Question 6

What is an extensive property and give examples

Answer 6

a property that depends on an object’s mass such as weight and momentum.

Question 7

for a BCC, what is the lattice parameter equation (a)

Answer 7

a=(4/√3) r

where r is the atomic radius

Question 8

for a FCC, what is the lattice parameter equation (a)

Answer 8

a=(2√2) r

where r is the radius

Question 9

what is used to represent: Plane, Collection of Planes, Direction, Collection of directions

Answer 9

Plane - (x y z)
Collection of planes - { }
Direction - [x y z]
Collection of directions - < >

Question 10

What is the equation for lateral strain

Answer 10

εx = -l/d
l = length
d= diameter

Question 11

what is the bond stiffness equation

Answer 11

S=Ea0
E = Young’s Mudulus
a0 = atomic spacing

Question 12

what is the value of a for a central crack

Answer 12

1/2 x length

NOT = LENGTH

Question 13

What are the (111) plane directions?

Answer 13

[1 -1 0] [1 0 -1] [0 1 -1]

Question 14

What plane does slip occur on for FCC and HCP

Answer 14

FCC - {1 1 1}

HCP - Close Packed Plane

Question 15

What is the value for critical resolved sheer stress along a slip direction

Answer 15

τc=σ cos⁡φ cos⁡λ

τc = tauc

Question 16

What is the equation for cos⁡φ in the critical resolved shear stress equation?

Answer 16

cos⁡φ=((Slip)⋅(Load))/|Slip|*|Load|

Question 17

What is the equation for cos⁡λ in the critical resolved shear stress equation?

Answer 17

cos⁡λ=([Direction]⋅(Load))/|Slip|*|Load|

Question 18

when is the critical resolved stress maximum

Answer 18

when φ or λ is 45

Question 19

When designing a pressure vessel, why do you want to use a ductile material?

Answer 19

So that it will leak before it breaks to prevent an explosion.

Question 20

how do you lay out a Brinell hardness test results

Answer 20

(hardness)Hb diameter(mm)/force(kgf)/time(s)

Question 21

What do D and d represent in the Brinell equation

Answer 21

D = ball diameter
d = impression diameter

Question 22

What is the rough strength for carbon fibre and diamond

Answer 22

10,000s MPa

Question 23

What is the rough strength for Steels

Answer 23

1000s MPa

Question 24

What is the rough strength for Bone and Cast iron

Answer 24

100s MPa

Question 25

What is the rough strength for Aluminium and Copper

Answer 25

10s MPa

Question 26

What is the rough strength for Polyethelene

Answer 26

1s MPa

Question 27

How do you calculate the yield stress

Answer 27

0.2% strain test

Question 28

what is the yield stress

Answer 28

The stress when a material’s elastic limit is reached and marks the onset of plastic deformation

Question 29

What is the ultimate tensile strength (UTS)

Answer 29

The maximum engineering stress that a material can support (the peak of the stress strain curve)

Question 30

what is the estimated value of v (poisson’s ratio) for metals

Answer 30

0.33

Question 31

What is poisson’s ratio

Answer 31

-lateral strain/normal strain
lateral = in x direction
normal = in z direction

Question 32

what is poisson’s ratio for cork

Answer 32

near 0