materials

Question 1

what is meant by breaking stress?

Answer 1

the maximum stress a material can withstand before fracturing

Question 2

what are examples of materials with a high breaking stress?

Answer 2

nylon, metals

Question 3

what are examples of materials with a low breaking stress?

Answer 3

glass, concrete

Question 4

what is meant by a brittleness?

Answer 4

the material can break quickly when subject to tensile stress

Question 5

what are some examples of brittle materials?

Answer 5

glass, ceramics

Question 6

what are some examples of non-brittle materials?

Answer 6

rubber, metals

Question 7

when does compressive force/stress occur?

Answer 7

when the applied force acts to squash a material

Question 8

what is meant by a creep?

Answer 8

the continual extension over a long period of time caused by a constant load

Question 9

what is a creep an example of?

Answer 9

plastic deformation

Question 10

what is density a measure of?

Answer 10

the concentration of matter within it

Question 11

what does density depend on?

Answer 11

the types of atoms from which the material is made and how they are combined

Question 12

what are examples of materials with a high density?

Answer 12

lead, gold

Question 13

what are examples of materials with a low density?

Answer 13

air, expanded polystyrene

Question 14

what is destructive testing?

Answer 14

where the material is damaged or destroyed by the testing process

Question 15

what are examples of destructive testing?

Answer 15

melting point, hardness

Question 16

what is meant by a dislocation?

Answer 16

an imperfection in the crystal lattice of a metal due to missing atoms

Question 17

how does a dislocation affect the crystal structure?

Answer 17

it deforms it as the atomic layers have to bend around the incomplete areas

Question 18

how can isolated dislocations move through a stressed structure?

Answer 18

by a process of atoms breaking and then remaking bonds

Question 19

what could happen if there was a large number of dislocations are created in a metal? (aka?)

Answer 19

they can become tangled which stops them moving and making the metal harder to deform (work hardening)

Question 20

what is meant if an object is ductile?

Answer 20

it can be drawn out into long threads by a tensile stress

Question 21

what is an example of a ductile material?

Answer 21

metals

Question 22

what are some examples of non-ductile materials?

Answer 22

glass, ceramics

Question 23

what happens during elastic deformation?

Answer 23

the bonds between atoms simply stretch, they dont break

Question 24

a stress- strain graph for elastic deformation is usually what kind of graph? (what is this proportionality called?)

Answer 24

a straight line (hooke’s law)

Question 25

what is an elastic limit?

Answer 25

the point beyond which elastic deformation ceases and plastic deformation begins

Question 26

what is electrical conductivity a measure of?

Answer 26

how easily electricity can flow through a material

Question 27

will a material with a high electrical conductivity be a good or poor conductor of electricity?

Answer 27

good

Question 28

will a material with a low electrical conductivity be a good or poor conductor of electricity? (meaning what?)

Answer 28

poor (its a good electrical insulator)

Question 29

what is the opposite of electrical conductivity?

Answer 29

electrical resistivity

Question 30

what do materials contain to be good conductors?

Answer 30

charged particles (usually electrons) that are free to move to carry electricity

Question 31

what are some examples of electrically conducting materials?

Answer 31

metals, graphite

Question 32

what are some examples of electrically insulating materials?

Answer 32

plastics, ceramics

Question 33

what is meant by endurance? (aka?)

Answer 33

the stress below which a material can withstand loading and unloading indefinitely without exhibiting fatigue (fatigue limit)

Question 34

what is an example of a high endurance material?

Answer 34

steel

Question 35

what is an example of a lowendurance material?

Answer 35

thermosetting plastics

Question 36

when does fatigue occur?

Answer 36

when a malleable material goes through repeated loading/unloading cycles which causes damage to the structure and the material eventually fractures

Question 37

what is a spring/force constant?

Answer 37

the ratio of the tensile force applied to a wire of spring to the extension produced

Question 38

how can the spring/force constant be found?

Answer 38

the gradient of a force-extension graph up to its limit of proportionality

Question 39

what is hardness a measure of?

Answer 39

how resistant an object is to plastic deformation

Question 40

what are some examples of hard materials?

Answer 40

glass, ceramics

Question 41

what are some examples of non-hard materials?

Answer 41

plastics, metals

Question 42

what is hooke's law?

Answer 42

the force applied to a wire/spring is directly proportional to the extension produced provided the limit of proportionality is not exceeded

Question 43

what is meant by hysteresis?

Answer 43

when the loading and unloading curves don't lie on top of each other

Question 44

what is meant by the limit of proportionality?

Answer 44

the point below which the force applied to a wire/spring is directly proportional to the extension produced