Mechanical Properties Flashcards
• What are the relevant properties of a material?
____
____
____ –> ___ ___ ____ ___ ___ ____
Biological properties, chemical properties, or physical properties (thermal, electrical, optical, corrosion, magnetic, mechanical)
Force any ___ that causes an object to ____ a ____ ____either concerning its ___ ___ or ____
F=
1lb= ___N
is any influence that causes an object to undergo a certain change,
either concerning its movement, direction, or geometrical structure.
Average Occlusal Forces on Natural Teeth
World’s Strongest Bite Record = ___ for __s
_____(mandibular angle)
and _____ should be
noted
Incisor = 150 N (34 lbs)
Cuspid = 200 N (45 lbs)
BiCuspid = 300 N (68 lbs)
Molar = 600 N (136 lbs)
Clenched teeth - 150 lbs/sq inch
World’s Strongest Bite Record = 975 lbs
for 2 seconds
According to 1992 Guinness Book of
Records in 1986 Richard Hofmann set
world record
Facial Form (mandibular angle)
and Muscle Definition should be
noted
Stress=
What is it? ___ ___ of an ___ ____
Unit
Force/Area= Sigma
Internal resistance of applied force
Unit: MPa
Types of stress
Axial:
- Tension +
- COmpression -
Shear
Torsion
Comparing strengths of materials
_____ is critical when comparing materials and when examining their ____ behavior.
Force per unit area (stress) is critical when comparing materials and when examining their mechanical behavior.
Strain
___ ___ ___
symbol
response to load
Epsilon
Flexural Strength Test
____ point ___ test performed using a ____ ____ ____ (____) under ____ ____
ASTM
ANSI
ADA
ISO
Three point bending test performed using a universal testing machine (Instron) under standardized conditions.
Strain
Strain is the ___ per unit ____
epsilon=____
epsilon=___
unit of measurement
Reported as
Strain is the deformation per unit of original length
epsilon= delta L / Lnot
epsilon=delta/Lnot
Strain has no unit of measurement since it is a ratio of length
to length and thus is a pure number.
Reported as
percentage.
Stress – Strain Curve
All stresses are based on the
Same 3 bars
Independent of
All stresses are based on the original cross sectional areas
Same 3 bars normalized by cross-sectional area (stress) and deformation normalized by original length (strain)
Independent of geometry of bar
Proportional limit
Initial portion of curve from 0 to P
o
o
After P
o
What is proportional limit? Value of ___ at P
o Its is the Highest ____ at which the stress/strain curve is a____’
Below the proportional limit
Sometimes e is the elastic point
o these terms often
§ it depends
· Initial portion of curve from 0 to P
o here Stress is linearly proportional to strain
o X2 strain X2 stress
· After P
o stress no longer linearly proportional to strain
· Value of Stress at P is the proportional limit
o Highest stress at which the stress/strain curve is a straight line’
· Below the proportional limit no permanent deformation taking place
· Sometimes e is the elastic point
o these terms often used interchangeably but not actually the same
§ it depends if you have very elastic material like if you have rubber band
A) Atoms without stress. B) Atoms under shear below proportional limit.
Atoms in B will return to original position when stress removed (reversible
A) Atoms without stress. B) Atoms under shear above proportional limit.
Atoms in B remain in new position when stress removed (irreversible).
Elastic region –
Plastic region –
Elastic region – region of stress-strain cure before proportional limit
Plastic region – region of stress-strain cure beyond proportional limit
YS = ___ ____,____ ____, ____ ____
A small defined ____ of _____ (i.e ___ offset) at which point the material begins to
A property that can be
Yield Strength (yield stress, yield point) a small defined percentage of stress (i.e., 0.2% offset) at which point the material begins to function in a plastic manner
o a property that can be determined readily
