materials Flashcards

(20 cards)

1
Q

does a higher young modulus mean a higher or lower stiffness

A

stiffness increases

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2
Q

define stress

A

force per unit area of cross section

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3
Q

define an elastic material

A

a material that returns to its original size and shape when the load deforming it has been removed

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4
Q

elastic limit / limit of proportionality

A

the maximum load which a body can experience and still regain its original size and shape once the load has been removed

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5
Q

hookes law

A

extension of an elastic object will be directly proportional to the force applied to it up to the object’s limit of proportionality.

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6
Q

what is the young modulus?

A

the ratio of stress to strain for a material

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7
Q

yield point

A

the yield point is the point reached where there is a marked increase in extension* when stress is increased beyond the elastic limit. *
**showing plastic behaviour beyond this point **
this is because the internal structre of the material has been changed and the material is said to be showing plastic behaviour.
few materials exhiit a yiled point (eg. mild steel does.)

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8
Q

what happens up to the limit of proportionality?

A

up to this point stress is proportional to strain and the gradient is the young’s modulus
F proportionl to e and returns to og length after force removed

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9
Q

what is strength?

A

relates to the maximum force which can be applied to a material without it breaking

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10
Q

what is breaking stress/ ultimite tensile strength (UTS)

A

maximum stress which can be applied to a material before fracture

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11
Q

what is stiffness?

A

relates to the resistance which a material offers to having its size and/or shape changed

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12
Q

what is a ductile material?

A

a material that can be permenantely streched

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13
Q

hardness

A

resistance to scratching

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14
Q

fatigue

A

a cause of fracture which occurs when a material is subjected to a large number of cycles of varying stress even of these stresses lie below the maximum that a material can withstand

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15
Q

what is creep?

A

used to describe the gradual increase in strain which occurs when a material is subjected to stress for a long period of time

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16
Q

breaking stress

A

The maximum stress that an object can withstand before failure occurs.

17
Q

what is spring constant?

A

the constant of proportionality for the extension of a spring under a force.
the higher the spring constant the greater the force needed to achieve a given extension

18
Q

what is tensile strain?

A

the ratio of an objects extension to its original length.
ΔL /L
no units

19
Q

what is Hooke’s law?

A

The extension of an elastic object will be directly proportional to the force applied to it up to the object’s limit of proportionality

20
Q

what is the limit of proportionality?

A

the point after which Hooke’s law is no longer obeyed