materials terms

Question 1

elastic limit

Answer 1

the point up to which the object will return to its original size and shape when the force is removed

Question 2

limit of proportionality

Answer 2

the point up to which the graph is a straight line & maximum extension the material can exhibit which is still proportional to the load

Question 3

plastic deformation

Answer 3

when the stress is removed, the object does not go back to its original size and shape - permanent set

Question 4

ultimate tensile strength

Answer 4

the maximum stress a material can bear, this occurs just before the material fails and fractures

Question 5

ductile

Answer 5

this material can be drawn into shapes using tensile forces

Question 6

brittle

Answer 6

this material has a tendency to fracture under stress. these materials can’t undergo plastic flow and are not suitable for manufacturing processes

Question 7

yield point

Answer 7

the point where the start of plastic flow causes a change of slope on the stress strain curve

Question 8

fatigue

Answer 8

the embrittlement and failure of material that can occur with low levels of stress if they are repeatedly applied

Question 9

creep

Answer 9

occurs when a material under stress deforms gradually over time - cold flow

Question 10

elastomer

Answer 10

objects made of rubber or synthetic polymers with rubber like properties which are able to exhibit large amounts of strain for relatively small levels of stress

Question 11

elastic hysteresis

Answer 11

occurs in material like rubber, when internal friction between large molecules dissipates energy producing heat. loading and unloading produces a different stress strain curve

Question 12

malleable

Answer 12

this material can be drawn into shapes using compressive forces

Question 13

define young’s modulus

Answer 13

property of a material that tells us how resistant to tensile and compressive forces it is - ratio of tensile stress to tensile strain

Question 14

low young’s modulus?

Answer 14

if the material stretches a lot for a small force

Question 15

large young’s modulus

Answer 15

stretches a very small amount with a large force

Question 16

tensile/compressive stress?

Answer 16

force per unit area applied, Nm-2

Question 17

tensile/compressive strain

Answer 17

ratio of extension to original length ( how much it has stretched)

Question 18

define tensile forces

Answer 18

force acting within a material that would extend the material

Question 19

define compressive forces

Answer 19

force acting within a material that would squash the material

Question 20

hooke’s law

Answer 20

the force required to stretch a spring is proportional to the extension of the spring up to the limit of proportionality

Question 21

what happens if the material is stretched beyond the elastic limit?

Answer 21

the material will no longer return to its original size - permanent set - plastic deformation