Chapter 6 - Materials Flashcards

1
Q

What are tensile forces?

A

Tensile forces are equal and opposite forces acting on a material to stretch it

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2
Q

What are compressive forces?

A

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

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3
Q

What are restoring forces?

A

Restoring forces return a system to its equilibrium position

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4
Q

What is tensile deformation?

A

Tensile deformation is when a helical spring experiences tensile forces

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5
Q

What is compressive deformation?

A

Compressive deformation is when compressive forces are exerted

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6
Q

What is Hooke’s Law?

A

Hooke’s Law states that the extension of a spring is directly proportional to the force applied

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7
Q

In what order does the limit of proportionality and elastic limit come?

A

The limit of proportionality comes before the elastic limit

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8
Q

How does an elastic body behave before the elastic limit?

A

Within the elastic limit, a spring experiences elastic deformation meaning it returns to original length when the force is removed

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9
Q

How does an elastic body behave after the elastic limit?

A

Past the elastic limit, the spring undergoes plastic deformation and experiences permanent structural changes

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10
Q

What is the relationship between force and extension?

A

Force is directly proportional to extension

Force = Spring Constant x Extension

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11
Q

What is the spring constant?

A

The spring constant is a measure of the stiffness

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12
Q

What are the steps of the Hooke’s Law Investigation?

A

Attach spring to one end using clamp, boss, and clam-stand secured to bench
Set up metre ruler
Suspend slotted masses form the spring
Record mass and new length of spring

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13
Q

What are the precautions used for the Hooke’s Law Investigation?

A

Take readings at eye level reducing parallax errors
Use digital balance
Repeat each reading at least once
Obtain at least 6 recordings

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14
Q

What does it mean if springs are in parallel?

A

When two springs hold up a mass from different points of connection

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15
Q

What does it mean if springs are in series?

A

When two springs attached to each other hold up a mass

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16
Q

How can the total spring constant be calculated for parallel and series?

A

Parallel springs:
ktotal = k1 + k2

Series springs:
1/ktotal = 1/k1 + 1/k2

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17
Q

How does energy behave within the elastic limit?

A

When a material is compressed/extended within the elastic limit, work done on a material can be fully recovered

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18
Q

How does energy behave during plastic deformation?

A

Plastic deformation moves atoms to new positions: energy is not recoverable

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19
Q

What is the formula for work done on a spring?

A

Work done = Force x Extension

Area under force-extension graph

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20
Q

What is the formula for elastic potential energy?

A

E = 1/2 * k * x2

E = 1/2 * F * x

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21
Q

What is the relationship between elastic potential energy and extension?

A

E is directly proportional to x2

22
Q

What is tensile stress?

A

Tensile stress is the force applied per unit cross-sectional area of the wire

23
Q

What is the formula for tensile stress?

A

Tensile stress = Force / Cross-sectional Area

24
Q

What is the formula for tensile strain?

A

Tensile Strain = Extension / Original Length

25
Q

What is the ultimate tensile strength?

A

Ultimate tensile strength is the maximum stress that a material can withstand before it breaks

26
Q

What is the breaking strength?

A

the stress value at the point of fracture is the breaking strength

27
Q

What is Young Modulus?

A

Young Modulus is the ratio of stress to strain

28
Q

What is relationship between stress and strain?

A

Stress is directly proportional to strain

29
Q

What is the formula for Young Modulus?

A

Tensile Stress / Tensile Strain

Pa or Nm-2

30
Q

What is the failure point?

A

Catastrophic failure total break of all bonds at one place

31
Q

What is the dislocation in a material?

A

The boundary between regions of a material that have slipped causing a misalignment of atomic planes

32
Q

What is the force required at the yield point?

A

At the yield point, the force required to move a dislocation is less that the force required to stretch atomic bonds

33
Q

How do the atoms in an elastic material act?

A

Metal cations increase in spacing as it is put under tension
Atomic separation returns to initial value when force removed
No energy lost in stretching

34
Q

How do atoms in a plastic material act?

A

Planes of atoms slide over each other
Dislocations allow plastic behaviour at lower stress
Dislocations allow bonds to be broken one at a time

35
Q

What are the effects of alloying?

A

Foreign atoms pin down dislocations making slips less likely
Planes move over shorter distances

36
Q

What are the properties of glass?

A

Brittle material
Strong as little extension for force
No plastic deformation

37
Q

What are the properties of steel?

A

Strong material
Not ductile
Breaks suddenly

38
Q

What are the properties of copper?

A

Strong material
Ductile
Deforms with plastic flow past elastic limit and yield points

39
Q

What are the properties of plastic?

A

Plastic flow from the start
Not strong
Small elastic region

40
Q

What is plastic flow?

A

Plastic flow occurs when a material under severe stress starts to behave as a fluid

41
Q

What is strength?

A

How much force is needed to break something
Not a fair test as some things are thicker

42
Q

What is breaking stress?

A

Breaking Stress = Breaking Force / Area

Force applied to the normal of an area

43
Q

What is stiffness?

A

How difficult it is to change the shape of the object

44
Q

What is brittleness?

A

Stiff, but not strong

45
Q

What is elasticity?

A

Ability of a material to regain its original shape after it is distorted

46
Q

What is plasticity?

A

Characteristic of a material to not regain its shape after distortion

47
Q

What is the relationship between the force as it is loaded and unloaded?

A

More force is required to load the spring rather than unload

48
Q

What does the area under a stress-strain graph show?

A

Total area is work done
Area between x axis and unloading line is elastic potential energy
Area between unloading and loading line is energy lost to heat

49
Q

How do you obtain an accurate diameter of a wire?

A

Taking multiple readings of the diameter along the wire

50
Q

How do brittle materials behave?

A

Brittle materials show elastic behaviour up to its breaking point without plastic deformation

51
Q

What are polymeric materials?

A

Polymeric materials consist of long molecular chains

52
Q

What do polymeric materials behaviour depend on?

A

Molecular Structure
Temperature