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Dental Materials > Properties of Materials > Flashcards

Properties of Materials Flashcards

1
Q

Stress is difficult to measure directly so the stress is calculated from the ratio of ___ per ___.

A

force per area

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2
Q

What are the 5 types of stress?

A

Tension Compression Shear Torsion Bending

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3
Q

___ - elongation forces are directed away from each other in the same straight line. molecules resist being pulled apart

A

Tension

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4
Q

___ - Shrinkage forces directed toward each other in the same straight line. Molecules resist being forced more closely together.

A

Compression

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5
Q

___ - Forces directed parallel to each other not along the same straight line. One portion resists sliding past the other.

A

Shear

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6
Q

___ - Twisting forces

A

Torsion

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7
Q

___ - Results from a bending moment

A

Bending

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8
Q

___ is a deformation caused by stress measured as a unit less value or as a %. (Deformation = deformation/length)

A

Strain

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9
Q

___ is the greatest stress sustained without deviation from the linear proportionality of the stress and strain

A

Proportional limit

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10
Q

___ is the greatest stress sustained without permanent deformation

A

Elastic limit

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11
Q

For ____ materials, the Proportional Limit and Elastic Limit represent the same stress within the structure.

A

linearly elastic

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12
Q

Elastic Deformation is ___ while plastic deformation is ___.

A

non-permanent permanent

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13
Q

___ is the stress at which the material begins to function in a plastic manner. Limited permanent strain has occurred.

A

Yield strength

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14
Q

Fun Fact about Yield Strength…

A

The exact point at which permanent deformation occurs is difficult to detect precisely so an arbitrary amount of deformation is chosen which can be measured accurately. Displayed as B on the graph.

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15
Q

Permanent deformation can be ___ or ___ in the oral cavity.

A

good or bad

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16
Q

What is an example of a constructive permanent deformation?

A

orthodontic wires must be bent to retain shape. Partial clasps must be readjusted

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17
Q

___ is the greatest stress an object can withstand.

It is represented by which letter on the graph?

A

Ultimate strength. Displayed as C on Strain/Stress graph

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18
Q

___ is the max stress that a material can withstand in tension.

A

Ultimate Tensile Strength (UTS)

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19
Q

___ is the max stress a material can withstand in compression

A

Ultimate Compression Strength (UCS)

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20
Q

___ is the stress at which a brittle material fractures.

A

Fracture Strength

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21
Q

A material does not always fracture at the point of greatest stress. It may elongate excessively reducing the cross-sectional area (called ____) causing a reduction in stress.

A

necking

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22
Q

___ is the deformation that results from the application or tensile force. It indicates the ___ of an alloy. Expressed as a %.

A

Elongation workability

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23
Q

___ is the measure of elasticity. Represents the stiffness of a material within the elastic region. The slope of the Stress/Strain curve in the elastic portion.

A

Elastic Modulus

24
Q

___ is the resistance of a material to permanent deformation. Indicates the amount of energy needed to deform a material to the ___ Limit.

A

Resilience Proportional

25
Q

___ is the resistance of a material to fracture.

A

Toughness

26
Q

Toughness is the combination of ___, ___, and ___.

A

Yield Strength, Ultimate Strength and Strain

27
Q

___ characterizes the behavior of materials with cracks or flaws.

A

Fracture mechanics

28
Q

Defects generally ___ a material and may result in fractures at stresses well below the yield stress. This occurs more in ___ materials that have no ability to deform and redistribute stresses.

A

weaken brittle

29
Q

Because tensile properties of ___ materials are hard to measure the ___ test is used.

A

brittle Diametral Compression

30
Q

____ is useful for comparing materials that are brittle and generally weak in tension. These materials will have both elastic and plastic properties but the ___ response is small.

A

Compression strength plastic

31
Q

___ is the stress at which a material fails under repeated loading This depends on the ___ of the load and the ___ of loadings.

A

Fatigue Strength magnitude, number

32
Q

___ is the stress at which the material can be loaded an infinite number of times without failing.

A

Endurance Limit

33
Q

Regarding viscoelasticity, Rate of ___ is important for many materials. Some properties of these are dependent on how fast they are stressed. Increasing the loading rate produces different S/S curves with ___ rates giving ___ values for E, PL, US

A

loading higher, higher

34
Q

Materials with mechanical properties dependent on loading rate are termed ____.

A

Viscoelastic

35
Q

___ is the resistance of a fluid to flow. It is often ___ and ___ dependent.

A

Viscosity time and temperature

36
Q

___ is an increase in strain in material under constant stress.

A

Creep

37
Q

___ is resistance to tearing forces. Depends on ___

A

Tear Strength rate of loading (Rapid loading = higher values)

38
Q

Slope A is ___ than the slope of B.

An equal stress produces a ___ strain in B than A

A

greater

greater

39
Q

What is represented by the yellow shaded area?

A

Resilience

40
Q

Characteristics of Graph 1

A

Stiff

Ductile

Strong

Tough

41
Q

Characteristics of Graph 2

A

Stiff

Brittle

Strong

42
Q

Characteristics of Graph 3

A

Stiff

Ductile

Weak

43
Q

Characteristics of Graph 4

A

Stiff

Brittle

Weak

44
Q

Characteristics of Graph 5

A

Flexible

Ductile

Strong

Resilient

45
Q

Characteristics of Graph 6

A

Flexible

Brittle

Strong

Resilient

46
Q

Characteristics of Graph 7

A

Flexible

Ductile

Weak

47
Q

Characteristics of Graph 8

A

Flexible

Brittle

Weak

48
Q

What materials are those that will fracture below their yield stress due to a flaw.

A

Glass, diamonds, sheetrock, models with bubbles, nicking adjacent enamel/porcelain.

49
Q

Between Yield Strength and Ultimate Strength, which is of more importance in dentistry and why?

A

Yield Strength may be of greater importance than Ultimate Strength in dentistry because it is an estimate of when a material will start to deform permanently.

50
Q

For most dental alloys and ceramics subjected to tension, the ___ and ___ will be similar

A

Ultimate Strength and Fracture Strength

51
Q

____ forces are responsible for the property of elasticity. The ___ the forces, the more stiff or rigid the material.

A

Interatomic/intermolecular

stronger

52
Q
A
53
Q

___ is compromised if a material has a defect

A

Fracture Toughness

54
Q
A
55
Q
A

Dental Materials (5 decks)

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