Materials Science

Question 1

Force

Answer 1

One body interacting with another generates force, causes deformation

Question 2

Max occlusal force range

Answer 2

200-3500 N

Question 3

Average force on bicuspids, cuspinds, incisors

Answer 3

300, 200, 150 N

Question 4

Child’s occlusal force

Answer 4

235-400 N, avg. yearly increase of 22 N

Question 5

Forces on partial dentures

Answer 5

65-235 N

Question 6

Forces on complete dentures

Answer 6

100 N molars and bicuspids, 40 N incisors

Question 7

Stress

Answer 7

= Force/Area. Internal reaction of force resisted by the body. Units are mega Pascals (MPa)

Question 8

Tension

Answer 8

Form of stress, two forces directed away from each other in a straight line

Question 9

Compression

Answer 9

Form of stress, two forces directed toward each other in a straight line

Question 10

Shear stress

Answer 10

Two sets of forces paralell to each other but not along the same straight line

Question 11

Torsion

Answer 11

Stress that results from the twisting of a body

Question 12

Bending/Flexural Stress

Answer 12

Stress that results from bending (like in a dental bridge)

Question 13

Strain

Answer 13

= Deformation/Original Length. Deformation of a body caused by stress, reported as a percentage.

Question 14

Stress-strain curve

Answer 14

Graphing Strain along X axis, Stress along Y axis. Must be compared among items of the same material and dimensions, though not necessarily the same shape.

Question 15

Proportional Limit

Answer 15

Amount of stress beyond which deformation is permanent and marks the limit of elastic deformation.

Question 16

Elastic limit

Answer 16

Maximum stress that a material will withstand without exhibiting further (more drastic) permanent deformation. Often coincides with proportional limit, unless material is Superelastic.

Question 17

Yield Strength

Answer 17

Stress at which materials begin to function in an aplastic manner. (Begin to break down)

Question 18

Ultimate Tensile/Compressive Strength

Answer 18

Maximum stress a material can withstand in tension/compression before failure

Question 19

Answer 19

A: Proportional Limit (PL)

B: Elastic Limit (EL)

C: Yield Strength/Ultimate Tensile Stress

D: Failure Point (FP)

Question 20

Fracture Stress

Answer 20

Point at which a brittle material fractures. If a material does not fracture, they will inlongate “necking”

Question 21

Elongation

Answer 21

= Increase in length/Original Length. Deformation as a result of the application of tensile force. Reported as %.

Question 22

Elastic Modulus

Answer 22

= Stress/Strain. Measure of elasticity, stiffness of a material within the elastic range. Slope of the Stress-strain curve.

Question 23

Poisson’s Ratio

Answer 23

During axial loading in tension or compression there is simultaneous strain in the axial and transverse/lateral directions. (If you stretch something out it gets skinny in the middle. If you squish something it gets fat in the middle.)

Question 24

Ductility

Answer 24

Ability to be drawn and shaped into a wire by tension.

Question 25

Malleability

Answer 25

Ability to be hammered or rolled into thin sheets without fracturing.

Question 26

Resilience

Answer 26

Resistance to permanent deformation. Indicates amount of energy necessary to deform to the PL.

Question 27

Toughness

Answer 27

Resistance to fracture. Indicates amount of energy necessary to cause fracture.

Question 28

Fracture Toughness (Kic)

Answer 28

The amount of energy required for fracture. Energy consumed in plastic deformation.

Question 29

Stiff/Flexible

Answer 29

Stiff: Will strain (deform) little with a large increase in stress. Flexible: Will strain much with a large increase in stress.

Question 30

Brittle/Ductile

Answer 30

Brittle: Brittle materials will fracture at the fracture stress. Ductile: Ductile materials will continue to deform beyond the fracture stress.

Question 31

Strong/Weak

Answer 31

Strong: Strong materials have high PLs Weak: Weak materials have low PLs

Question 32

Viscoelasticity

Answer 32

Mechanical properties depend on the loading rate and have both viscous and elastic behavior.

Question 33

Viscosity

Answer 33

Resistance of a fluid to flow. Fluid traits.

Question 34

Color

Answer 34

Objective analysis of the physical stimulus of a beam of light.

Question 35

Hue

Answer 35

Wavelength of light producing different colors. 400 nm Violet \> Blue \> Green \> Yellow \> Orange \> Red 700 nm

Question 36

Value

Answer 36

Quality of lightness or darkness. Black has low value, white has high value.

Question 37

Chroma

Answer 37

Quality of a color's purity, intensity, saturation.

Question 38

Metamerism

Answer 38

Metameric colors appear different under different lights because of different spectral energy distributions.

Question 39

Fluorescence

Answer 39

Emmision of luminous energy by a material when a beam of light is shone on it.

Question 40

Opacity

Answer 40

Property of material that prevents the passage of light.

Question 41

Translucency

Answer 41

Property that permits passage of light, but disperses the light so objects cannot be seen through the material.

Question 42

Opalescence

Answer 42

Materials that scatter shorter wavelengths of light (shine like an opal)