Jan Exam

Question 1

What is the equation for secondary creep strain rate?

Answer 1

Strain rate = K*sress^n *e^(-Q/RT)

Question 2

What temperature does strain rate occur?

Answer 2

T>0.4Tm

Question 3

How can you find Q? Graphically.

Answer 3

Gradient of ln(strain rate) v 1/T
T in Kelvin
Gradient = -Q/R

Question 4

How can you find n? Graphically

Answer 4

Gradient of ln(strain rate) v ln(stress)

Gradient = n

Question 5

What is Larson Miller Parameter used for?

Answer 5

Extrapolation

Question 6

What is the equation for LMP?

Answer 6

LMP = T(C+logtr)

Where tr = rupture lifetime (in hours)
C normally equals 20

Question 7

How do you find LMP?

Answer 7

From a graph, tr can then be calculated from it.

Question 8

How is creep strain related to time?

Answer 8

Strain = Strain rate * time

Question 9

Is creep strain total strain?

Answer 9

NOOO!
Total strain = creep strain + steady state/instantaneous/primary

Normally given

Question 10

How would i take 1.5x10^6 as a strain rate?

Answer 10

Make it 0.15x10-7 and use that value on the graph.

Question 11

What type of brackets are used for directions?

Answer 11

Square for individual, triangular for family

Question 12

What brackets are used for planes?

Answer 12

circle for individual and curved for family

Question 13

How do you find interceptions of planes?

Answer 13

Planes given in miller indices,
Interception = 1/miller indices.
Note: if infinite then it doesnt touch that axis.

Question 14

What is linear density?

Answer 14

Number of atoms centred on vector/length of vector

Note: number means throughout whole of cube in that direction.

Question 15

What is planar density?

Answer 15

Number of atoms centred on plane/ Area of plane

Question 16

How is a related to r in BCC

Answer 16

root3 a = 4r

Question 17

How is a related to r in FCC

Answer 17

root2 a = 4r

Question 18

What is the atomic packing factor?

Answer 18

Volume of atoms in cell / Volume of cell

Note: atoms volume = 4/3 Pi r^2
Volume of cell = a^3

Question 19

What is the equation for theoretical density?

Answer 19

density = Number of atmos * Atomic mass / Volume of cell * Avogadros number

Note: number of atoms in FCC = 4 BCC=2
Avogadros Number = 6.02x10^23

Question 20

What wt%C do Cast Irons have?

Answer 20

2.14 - 4.5% (after steels)

Question 21

What are the types of cast iron?

Answer 21

Gray, nodular, white, malleable, compact graphite

Question 22

How do you get pearlitic maleable cast iron?

Answer 22

Fast cooled hot white cast iron.

Question 23

How do you get Ferritic maleable cast iron?

Answer 23

Slow cooled hot white cast iron

Question 24

What does higher damping capacity do?

Answer 24

Reduce chatter

Question 25

What type of castings are there?

Answer 25

Sand, Die, Investment, Continuous, Fabrication

Question 26

What Aluminium alloys are heat treatable?

Answer 26

2, 6, 7

Question 27

What Aluminium alloys are Strain hardened?

Answer 27

1, 3, 5, 8

Question 28

What is precipitation hardening also called?

Answer 28

Age hardening

Question 29

What is strength?

Answer 29

Max load at failure, highest stress

Question 30

What is ductility?

Answer 30

Ability to deform

Question 31

What is Hardness?

Answer 31

Resistance to deformation, indented test

Question 32

What is stiffness?

Answer 32

Resistance to elastic deformation, stress/strain Youngs Modulus

Question 33

What is the Ultimate strength?

Answer 33

Peak on curve before necking

Question 34

How do you find the yield if it is unclear?

Answer 34

0.2% straight line same gradient

Question 35

What is the area under a stress strain graph?

Answer 35

Toughness (impact energy that can be absorbed)

Question 36

What is poissons ratio?

Answer 36

v = -lateral strain / logitudinal strain = -delta diameter/diameter. / delta length/length.

Question 37

What is bulk modulus?

Answer 37

K To do with pressures on object P=-K deltaV / V

Question 38

What is shear modulus?

Answer 38

G Torsion torque = Gy Where y = displaced angle

Question 39

How is poissions ratio related to other moduli?

Answer 39

V = E/2G - 1

Question 40

How is ductility measured?

Answer 40

Strain at failure %EL = Lf - Lo /Lo Or same with areas

Question 41

What is engineering stress?

Answer 41

Original area used

Question 42

What are point defects?

Answer 42

0D Vacancies, Interstitials, Substitutionals, Frenkel, Shottky

Question 43

What are line defects?

Answer 43

1D Dislocations (screw,Edge)

Question 44

What are planar defects?

Answer 44

Grain boundries, Stacking falts

Question 45

What are bulk defects?

Answer 45

Pores, inclusions, cracks

Question 46

Are defects useful?

Answer 46

They give a material its mechanical properties So YEA! always in materials

Question 47

What is the AISI - SAE system?

Answer 47

XYWZ where X = group of carbon steel Y = Amount of alloying element WZ = Carbon concentration (20 = 0.2%)

Question 48

What are these parts of a phase diagram called? | alpha, gamma, Fe3C, Fe3c + alpha

Answer 48

In order, | Ferrite, Austenite, Cemetite, Pearlite

Question 49

What are the 2 phase diagram reactions and what are they?

Answer 49

Eutectoid ( gamma - alpha +Fe3C) | Eutectic ( Liquid - gamma + Fe3C)

Question 50

at what wt%C is a eutectoid steel?

Answer 50

0.76

Question 51

What are the other steels in the phase diagram?

Answer 51

Hypoeutectiod, eutectoid, hypereutectoid

Question 52

What are the WT%C of ferrite and cementite?

Answer 52

0.02% and 6.7%

Question 53

How do you use the lever rule?

Answer 53

Amount of LHS weighting = RHS / Total length Amount of RHS weighting = LHS / Total length Limits are 0.02 for ferrite, 0.76 (proutectiod) austenite, 6.7 cementite

Question 54

What are the compositions of the following microstructures? Hypoeutectiod, eutectoid, hypereutectoid

Answer 54

ferrite + Prelite 100% pearlite cementite + pearlite

Question 55

How do you find the composition of each phase?

Answer 55

draw straight line horizontally to the end of each phase, these will give you the wt% of one element, use this to find the other.

Question 56

How is the strain energy release rate calculated?

Answer 56

G = stress*pi*a / E a = half the length of the crack

Question 57

How do you calculate the critical stress?

Answer 57

= (2*E*ys/pi*a)^1/2 where ys = specific surface energy

Question 58

How do you calculate the fracture toughness?

Answer 58

K = Y*stress*root(pi*a) if K > Critical toughness then it will fail. (critical toughness determined using critical strength) Y= material constant.

Question 59

How do you produce matensite?

Answer 59

Quenching: heating to above recrystalisation temp and cooled rapidly in water or oil. It can then be temered to regain ductiity by heating to below recrystalisation temp and cooled slowly at room temp

Question 60

What will Austenite turn into when cooled at different rates? From a non equilibrium phase digram.

Answer 60

``` Slow = Pearlite Medium = Bainite Fast = Martensite ```

Question 61

How do you calculate the stress concentration factor?

Answer 61

Kt = (1 + 2a/b) Measure of how much the stress is amplified Where a = width and b = height of hole/crack

Question 62

What to do when given t bars with fillet radius (stress concentrators)

Answer 62

find r/d, look at graph to find Kt for given D/d (may need to interpolate) finds stress using smaller d and force Max stress = SCF * stress

Question 63

What is the graph for cyclic loading?

Answer 63

Stress amplitude vs cycles to failure

Question 64

How do you calculate the amplitude on cyclic loading?

Answer 64

half of (max stress - min stress)

Question 65

How do you find mean stress?

Answer 65

max stress + min stress / 2

Question 66

What type of question could we get for cyclic loading?

Answer 66

To find max and min stress, Find equations for them using mean and amplitude, Solve simultaneously

Question 67

3 notes for phase diagrams

Answer 67

always give compositions of both elements in phase when pre eutectic, phase grows in grain boundries (give compositions of these phases too) Always draw straight line to either side if mixed phase. Useful for lever rule and wt%

Question 68

What are the wt%C of the following metals? | Wrought Iron, Steel, Cast Iron

Answer 68

<6.7

Question 69

How do you calculate the coefficient of thermal expansion?

Answer 69

strain = Alpha(T2-T1)

Question 70

What is the bond energy and how do other factors change as it increases?

Answer 70

The energy to create or break a bond between atoms. As Bond energy increases: Melting temp increases, Coef of thermal exp decreases, Elastic modulus increases

Question 71

What is the Hall-Patch Equation?

Answer 71

Yield strength = Stress. + Ky*d^-0.5 Where stress. and Ky are material constants d = average grain diameter