Materials Science Flashcards
Force
One body interacting with another generates force, causes deformation
Max occlusal force range
200-3500 N
Average force on bicuspids, cuspinds, incisors
300, 200, 150 N
Child’s occlusal force
235-400 N, avg. yearly increase of 22 N
Forces on partial dentures
65-235 N
Forces on complete dentures
100 N molars and bicuspids, 40 N incisors
Stress
= Force/Area. Internal reaction of force resisted by the body. Units are mega Pascals (MPa)
Tension
Form of stress, two forces directed away from each other in a straight line
Compression
Form of stress, two forces directed toward each other in a straight line
Shear stress
Two sets of forces paralell to each other but not along the same straight line
Torsion
Stress that results from the twisting of a body
Bending/Flexural Stress
Stress that results from bending (like in a dental bridge)
Strain
= Deformation/Original Length. Deformation of a body caused by stress, reported as a percentage.
Stress-strain curve
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.
Proportional Limit
Amount of stress beyond which deformation is permanent and marks the limit of elastic deformation.
Elastic limit
Maximum stress that a material will withstand without exhibiting further (more drastic) permanent deformation. Often coincides with proportional limit, unless material is Superelastic.
Yield Strength
Stress at which materials begin to function in an aplastic manner. (Begin to break down)
Ultimate Tensile/Compressive Strength
Maximum stress a material can withstand in tension/compression before failure
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A: Proportional Limit (PL)
B: Elastic Limit (EL)
C: Yield Strength/Ultimate Tensile Stress
D: Failure Point (FP)
Fracture Stress
Point at which a brittle material fractures. If a material does not fracture, they will inlongate “necking”
Elongation
= Increase in length/Original Length. Deformation as a result of the application of tensile force. Reported as %.
Elastic Modulus
= Stress/Strain. Measure of elasticity, stiffness of a material within the elastic range. Slope of the Stress-strain curve.
Poisson’s Ratio
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.)
Ductility
Ability to be drawn and shaped into a wire by tension.
Malleability
Ability to be hammered or rolled into thin sheets without fracturing.
Resilience
Resistance to permanent deformation. Indicates amount of energy necessary to deform to the PL.
Toughness
Resistance to fracture. Indicates amount of energy necessary to cause fracture.
Fracture Toughness (Kic)
The amount of energy required for fracture. Energy consumed in plastic deformation.
Stiff/Flexible
Stiff: Will strain (deform) little with a large increase in stress.
Flexible: Will strain much with a large increase in stress.
Brittle/Ductile
Brittle: Brittle materials will fracture at the fracture stress.
Ductile: Ductile materials will continue to deform beyond the fracture stress.
Strong/Weak
Strong: Strong materials have high PLs
Weak: Weak materials have low PLs
Viscoelasticity
Mechanical properties depend on the loading rate and have both viscous and elastic behavior.
Viscosity
Resistance of a fluid to flow. Fluid traits.
Color
Objective analysis of the physical stimulus of a beam of light.
Hue
Wavelength of light producing different colors. 400 nm Violet > Blue > Green > Yellow > Orange > Red 700 nm
Value
Quality of lightness or darkness. Black has low value, white has high value.
Chroma
Quality of a color’s purity, intensity, saturation.
Metamerism
Metameric colors appear different under different lights because of different spectral energy distributions.
Fluorescence
Emmision of luminous energy by a material when a beam of light is shone on it.
Opacity
Property of material that prevents the passage of light.
Translucency
Property that permits passage of light, but disperses the light so objects cannot be seen through the material.
Opalescence
Materials that scatter shorter wavelengths of light (shine like an opal)