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define the load/elongation curve
L/E curve takes into consideration the geometry of the specimen aka extrinsic stiffness
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define S/S curve
normalizes out geometry aka intrinsic stiffness
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true/false: elastic modulus can be obtained from a L/E curve
false. it cannot be obtained from the L/E curve
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define proportion limit
point at which any permanent deformation is first observed
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define yield point
deformation of 0.1%, wire will not return to its original state
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define ultimate tensile strength
maximum load, greater than yield strength
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define failure point
point at which the wire breaks
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define stiffness
proportional to elastic modulus. steeper slope = stiffer wire.
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define springness
1/stiffness or 1/elastic modulus. more horizontal the slope = springier wire.
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define range
distance wire will bend elastically before permanent deformation
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define strength
stiffness x range
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define resiliance
area under S/S curve from 0 to proportional limit/yield stength
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define formability
amount of permanent bending the wire will tolerate before it breaks or fails. area under S/S curve from YP to FP
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what happens to strength, stiffness, springiness and range if the diameter is increased?
- increase: strength, stiffness
- decrease: springiness, range
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what happens to strength, stiffness, springiness and range if the length is increased?
- increase: springiness, range
- decrease: strength, stiffness
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round or rectangular wires elicit more force?
rectangular (more stiffness)
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list 4 ways loops are used in arch wires
- 1. align teeth
- 2. increase force of the wires
- 3. increase flexibility of wires
- 4. hold soft tissues away from orthodontic brackets
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