Biochem Simplified Flashcards by Gracie Comeau

2 reasons we measure mechanical properties

to obtain fundamental properties and to see what properties will affect the material in its final conditions

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fundamental properties

strength

elasticity

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applied properties

impact
fatigue
abrasion

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1st classification of mechanical properties

bulk: whole mass - strength, elasticity
surface: first few layers of atoms - hardness, wear

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resistance to indent

hardness

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resistance to abrasion

wear

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Fundamental - steadily increase load (stress-strain)

Applied - single sudden force (impact), repeated low load (fatigue), time dependent (viscoelastic - plastic bag example)

2nd classification of mechanical properties - Bulk subclassifications (fundamental and applied)

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force per unit area, arises from externally applied forces

stress

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stress units

Pa, MPa

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force/area= stress

calculation

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arrows away

tension

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arrows towards

compression

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bar parallel to the ground, one arrow on top one on bottom

sheer

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compression, tension and sheer

torsion

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compression and tension

flexure/binding

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tensions makes things ___ compared to compression

weak, crack

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strain is to ____ as stress is to ____

strain is to deformation as stress is to load

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strain calculation

change in L / L(i). or L(f)-L(i)/L(i)

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elastic strain is

recoverable

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plastic strain is

permanent

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phases of plastic and elastic while recording an impression

plastic on insertion(perm) and elastic on displacement from tissue (recoverable)

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O –> A on the stress/strain graph is linear and elastic because it hasn’t reached the breaking point so it is _______

recoverable

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Law that states that up until A on the stress/strain graph, stress and strain are proportional to each other

Hookes Law

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What is that linear portion of the stress/strain graph called and what region does it represent (up until A)

Called the Modulus of Elasticity and is defined as the elastic region of the material

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Modulus of elasticity is a measure of ______ / _____-

rigidity/stiffness

High modulus: ____ rigid

Low modulus: ____ rigid

less

A,B,C on stress/strain graph

A: proportional limit B: elastic limit C: yield point (PEY for your ABC's lol)

Stresses below B on the stress/strain graph

elastic

Stresses above B on the stress/strain graph

plastic

Stress at B called

Elastic Limit

Yield point is the point where _____ strain becomes very pronounced

plastic

Reminder - all values of stress on the _ axis

Ductility and Malleability are measures of ___ of ____

% of elongation

High % of elongation: ____ material

ductile

Low % of elongation: ____ material

brittle

relating to TENSION: ductility is the measure of something's ability to form a ____ shape

wire

relating to COMPRESSION: malleability is the measure of the ability to be _____ into a ____

hammered into a sheet

Elongation is a value of ____

strain (X axis)

OBD triangle on stress/strain graph

Mod. of resilience

Total area under stress/strain graph

Toughness - area units J/m3

Total energy a material can absorb until fracture

toughness

amount of energy a material can absorb without permanently deforming

resilience

hardness indenter circle shape

brinell

hardness indenter small diamond

vickers

hardness indenter long diamond

knoop

what is time dependent (plastic bag stress over time)

viscoelasticity

deform under constant pressure/stress over time

creep

monomers + monomers

polymeric molecules

polymeric molecules + polymeric molecules

polymeric material

ID condensation reactions: Si and O, NO C, eliminating H2O

Silicones

ID condensation reactions: eliminate NaCl

Polysulfides

ID condensation reactions: Chain of C, eliminate H2O

Nylon

Addition / vinyl compound's two shining stars of the show

Acrylics - resin and acid

hard rigid glass polymer, liquid and then at dentists final polymer is synthesized

Acrylic resin

adhesive water soluble polymer, liquid and ready to be used

Acrylic acid

Common example of vinyl compound / acrylic resin in dentistry

Methacrylate --> PMMA (dentures/dental cements)

G(2)PT - 4 stages of polymerization

``` Generation of free radicals - activation (heat/light) - initiation (at molecular level) Propagation of rxn Termination of rxn ```

SAP that alter one another

structure, properties, application

spaghetti example is referring to polymeric materials

length, temp, alignment, disentanglement, sauce

DoP

of repeat units/monomers

DoP x MW of repeating units (in g/mol usually)

Higher the MW, higher the ____/____

strength/rigidity

Higher the DoP, Higher the strength because

more bonds to break

3 physical states of polymers (EAS)

``` Elastomers Hard amorphous (transparent) Hard semicrystalline (translucent) ```

why are polymers more flexible at higher temp

easier disentanglement

High Tg leads to

rigid at room temp

Low Tg leads to

flexible at room temp

High Tg - RIGID (hard polymers)

Low Tg - FLEXIBLE (elastomers)

elastics is to ___ and viscous is to break intermolecular bonds and ____

stretch, disentanglement

plasticizers liquids that reduce friction between molecules and ____ and lower Tg

Soften, lower Tg

Cross linking leads to more bonds and results in (3 things)

stronger, more rigid, higher Tg

lead to different arrangements at molecular level (SAME COMPOSITION THO) and results in different properties

co polymers

impressions, rubber for root canal, resin composites are all examples of

polymer application in dentistry

mixture of metals

alloy

metals are polycrystalline which means long, regular arrangement of atoms. in contrast, _____ has no such regularity

amorphous

point imperfections (3)

substitutional, interstitial, vacancies

line imperfection results in ____ in a crystal

dislocation

metal with smaller grains results in a ____, tough and dense but more corrosive metal

strong

plastic deformations in metals results in slip of layers of atoms over each other and is __

permanent

soft metal is one where ___ can be easily moved through crystal structure

easily

makes more dislocations, more interactions between dislocations which makes stronger

cold working

grain growth - from heating, larger grains form, less impediment for dislocation

softer material

to have a solid substitutional you need the same lattice structure and similar ___ size

atomic (au, Cu, Ag, Pt, Pd -- FCC)

Steel C atoms in Fe - since carbon is so small compared to Fe results in

Solid interstitial. results in stainless steel and makes dislocation harder

You have metal A and metal B. have a combo of both then that is a variable combo

partial solid insolubility.

metals make compounds but they are very specific and defined composition ex: Ag3Sn - amalgam

Intermetallic compounds

strong, stiff, brittle, but chemically stable and noncorrosive

ceramics

Biochem Simplified Flashcards

(88 cards)