06 - materials

Question 1

extension

Answer 1

the increase in length of an object when a tensile force is exerted on it

Question 2

tensile force

Answer 2

equal and opposite forces acting on a material to stretch it

Question 3

compression

Answer 3

the decrease in length of an object when a compressive force is exerted on it

Question 4

compressive force

Answer 4

two or more forces together that reduce the length or volume of an object

Question 5

tensile deformation

Answer 5

a change in the shape of an object due to tensile forces

Question 6

compressive deformation

Answer 6

a change in the shape of an object due to compressive forces

Question 7

force-extension graph

Answer 7

a graph of force against extension (or compression) with the area under the graph equal to the work done on the material

Question 8

elastic limit

Answer 8

the value of stress or force beyond which elastic deformation becomes plastic deformation, and the material or object will no longer return to its original shape and size when the stress or force is removed

Question 9

elastic deformation

Answer 9

a reversible change int he shape of an object due to a compressive or tensile force - removal of stress or force will return the object to its original shape and size (no permanent strain)

Question 10

plastic deformation

Answer 10

an irreversible change in the shape of an object due to a compressive or tensile force - removal of the stress or force produces permanent deformation

Question 11

Hooke’s law

Answer 11

the force applied is directly proportional to the extension of the spring unless the limit of proportionality es exceeded

Question 12

force constant

Answer 12

a quantity determined by dividing force by extension (or compression) for an object obeying Hooke’s law - called constant of proportionality k in Hooke’s law, measured in Nm^-1

Question 13

stiffness

Answer 13

the ability of an object to resist deformation

Question 14

elastic potential energy

Answer 14

the energy stored in an object because of its deformation

Question 15

loading curve

Answer 15

a force-extension graph

Question 16

hysteresis loop

Answer 16

a loop-shaped plot obtained when, for example, loading and unloading a material to produce different deformations

Question 17

tensile stress

Answer 17

the force per unit cross-sectional area, measured in Pa

Question 18

tensile strain

Answer 18

the extension per unit length, a dimensionless quality

Question 19

ductile

Answer 19

property of a material that has a large plastic region in a stress-strain graph, so can be drawn into wires

Question 20

limit of proportionality

Answer 20

the value of stress or force beyond which stress is no longer directly proportional to strain

Question 21

yield point

Answer 21

a point on a stress-strain graph beyond which the deformation is no longer entirely elastic

Question 22

ultimate tensile strength

Answer 22

the maximum stress that a material can withstand before it breaks

Question 23

breaking strength

Answer 23

the stress value at the point of fracture, calculated by dividing breaking force by cross-sectional area

Question 24

strong material

Answer 24

a material with a large value for the ultimate tensile strength

Question 25

Young modulus

Answer 25

the ratio of tensile stress to tensile strain when these quantities are directly proportional to each other, measured in Pa

Question 26

polymeric

Answer 26

description of a material compromising of long-chain molecules, such as rubber, which may show large strains

Question 27

brittle

Answer 27

property of a material that does not show plastic deformation and deform very little (if at all) under high stress