materials 1

Question 1

what are some elements to consider when selecting materials for a purpose? (5 points)

Answer 1

1. fitness for purpose
2. construction techniques
3. cost
4. sustainability
5. aesthetics

Question 2

what do you consider when looking at fitness for purpose? (3 points)

Answer 2

1. ability to withstand loads, such as strength (yield and tensile strength) and failure (toughness)
2. dimensional stability (modulus, hardness, creep and expansion due to thermal and moisture)
3. durability (maintenance such as corrosion, wear and fire)

Question 3

what do you consider for construction techniques? (3 points)

Answer 3

1. manufacture
2. assembly
3. finishing

Question 4

what do you consider for cost?
(4points)

Answer 4

1. construction materials
2. medium engineering
3. special materials
4. industrial diamonds

Question 5

what do you consider for sustainability? (4 points)

Answer 5

1. availability of resources
2. energy content
3. utilisation and storage of wastes
4. recycling

Question 6

what do you consider for aesthetics? (3 points)

Answer 6

1. appearance
2. texture
3. feel

Question 7

what material cost groups are in the Ashby diagram? (7 points)

Answer 7

1. foams
2. metals and alloys
   3.polymers
3. natural materials
4. composites
5. ceramics
6. elastomers

Question 8

name the families of materials:
(6 points)

Answer 8

1. hybrids
2. glass
3. metals
   4.ceramics
4. elastomers
5. polymers

Question 9

define strong

Answer 9

ability to carry load or force

Question 10

define stiff

Answer 10

ability to resist deflection

Question 11

define toughness

Answer 11

ability to resist fracture

Question 12

define light weight

Answer 12

ability to perform without adding too much additional weight

Question 13

name the type of material properties (7 points)

Answer 13

1. thermal
2. optical
3. electrical
4. mechanical
5. eco
6. processability
7. general

Question 14

whats the equation of stress?

Answer 14

force/area (N/m^2)

Question 15

whats the equation of strain?

Answer 15

change in length/ original length (dimensionless)

Question 16

whats the equation for shear stress?

Answer 16

shear force/shear area (N/m^2)

Question 17

whats the equation for shear strain?

Answer 17

deflection/original length (dimensionless)

Question 18

whats the equation of young’s modulus?

Answer 18

stress/strain (N/m^2 or Pa)

Question 19

whats elastic modulus?

Answer 19

in the elastic region, stress is proportional to strain

Question 20

whats the stress at the elastic limit called?

Answer 20

yield strength

Question 21

why are tensile and compression tests not always convenient?

Answer 21

needs a large sample that ends up getting destroyed

Question 22

whats the advantage of using a hardness test?

Answer 22

gives an approximate, non destructive measure of strength

Question 23

how is the hardness of a material measured?

Answer 23

by pressing a pointed diamond or hardened steel ball into the surface of the material

Question 24

whats hardness measured in?

Answer 24

(MPa)

Question 25

whats the equation of hardness?

Answer 25

force/area (MN/m^2 or MPa)

Question 26

whats creep?

Answer 26

time dependent strain at constant stress