Testing Materials

Question 1

Hard

Answer 1

Difficult to scratch

Question 2

Brittle

Answer 2

Fractures with little plastic deformation when subjected to stress
Even the strongest of brittle materials absorb relatively little energy

Question 3

Stiff

Answer 3

Difficult to bend or stretch

High Young’s Modulus

Question 4

Malleable

Answer 4

Easily shaped

Question 5

Ductile

Answer 5

Can be drawn into wires

Question 6

Tough

Answer 6

Can undergo considerable amounts of deformation before fracture
Absorbs relatively large amounts of energy

Question 7

Soft

Answer 7

Easy to alter through thermal fluctuations and external forces

Question 8

Ceramics - properties

Answer 8

Hard
Brittle 
Stiff
High melting point
Poor conductivity
High resistance to corrosion and wear

Question 9

Metals - properties

Answer 9

Malleable 
Ductile
Good conductivity
Melting points vary
Pure metals are soft
Alloys are harder

Question 10

Glassy polymers - properties

Answer 10

Similar to glass
Brittle
Able to replace glass in spectacles

Question 11

Semi-crystalline polymers - properties

Answer 11

Tough

Question 12

Hooke’s Law

Answer 12

F = kx

Question 13

Energy stored in a spring

Answer 13

E = 1/2 kx^2

Question 14

Elastic deformation

Answer 14

Where the material will return to its original shape when the stress is removed

Question 15

Plastic deformation

Answer 15

Where the material will not return to its original shape when the stress is removed

Question 16

Elastic limit

Answer 16

When a material begins to deform plastically

Question 17

Stress

Answer 17

Force / C-S Area

Question 18

Strain

Answer 18

Extension / Original length

Question 19

Stress/Strain graphs

Answer 19

Linear in elastic region
Yields at elastic limit
Increases much slower as it hardens
Begins to decrease slightly as it necks
Fractures at the fracture point

Question 20

Young’s Modulus

Answer 20

YM = stress/strain
= (F/A) / (x/L)
= FL / Ax
Is constant for every material despite dimensions

Steel: 100 GPa
Polymers: 1 GPa

Question 21

Density

Answer 21

Mass / Volume

Question 22

Tension

Answer 22

A force acting to stretch a material

Question 23

Tensile strength

Answer 23

Resistance of a material to elongate

Steel: 1000 MPa
Polymers: 100 MPa

Question 24

Compression

Answer 24

A force acting to squash or compress a material

Question 25

Compressive strength

Answer 25

Resistance of a material to reduce in size

Question 26

Strength

Answer 26

Ability to withstand stress without failure