Week 2: Mechanical Properties Flashcards
classification of mechanical properties
1st classifications: bulk/surface
2nd classifications: sub-classifications of bulk properties (fundamental, applied)
force per unit area from externally applied forces
stress
unit of stress
Pa/MPa
fundamental types of stress
tension, compression, shear
force perpendicular to resisting area
tension
force perpendicular to resisting area, sense of load opposite to that of tension
compression
force parallel to resisting area
shear
combined types of stress
torsion, flexure/bending
where does stress concentrate?
notches, grooves, cracks, surface irregularities
describes relative deformation or change in shape and size with respect to initial length under applied forces (stresses)
strain
strain that is recoverable
elastic
strain that is permanent
plastic
high modulus equals what type of material?
rigid material
low modulus equals what type of material?
less rigid material
Stresses _______ than the
elastic limit produce permanent/plastic deformation in the material.
equal to or higher
Stress at which material changes from elastic to plastic strain
elastic
ductility/malleability is measured by what
% of elongation
high % ductility/malleability equals what?
ductile material
low % ductility/malleability equals what?
brittle material
stress at which material breaks, last point in stress-strain curve
Ultimate Tensile Strength (UTS)
Maximum stress the material undergoes during stress-strain test
maximum stress
Amount of energy a material can absorb without permanently deforming
resilience
Total amount of energy a material can absorb until fracture
toughness
ability for material to resist indentations, resistance to be scratched
hardness
loss of anatomic form from surface or restoration, results in wear
abrasion
Repeated low forces (below elastic limit) that bring the material to an unexpected fracture
fatigue stress
a key note about viscoelasticity, or combination of viscous and elastic behavior, is that it is __ _____
time dependent
slow deformation with time under constant stress
creep
material constantly deformed, may show drop in stress to keep deformation with time
stress relaxation
laboratory tests (__ _____) ____ predict ___ ______ behavior
in vitro, cannot, in vivo
consideration of the whole mass of material
bulk properties
examples of bulk properties
strength, elasticity, etc.
examples of surface properties
hardness, wear, etc.
sub-classification of bulk properties
fundamental properties, applied properties
stress is applied from…
external forces
calculations of stress
Force (F) / cross-sectional area (A)
strain is…
dimensionless
in stress-stain graph…
y axis =
x axis =
y axis = stress AND strength
x axis = strain
area under curve of stress-strain graph is…
values of force per displacement (work)
linear part of the graph is…
elastic strains
flexibility (is/is not) a fundamental property
is NOT
change from elastic to plastic strain points
“PEY”
proportional limit
elastic limit
yield point
if you go above ___ ____, restorations will fail
elastic limit
maximum strength is found at the _______
highest point of the graph
malleability: ability of a material to be formed into a ____
sheet
ductility: ability of a material to be formed into a ____
wire
in stress-strain graph, area underneath linear slope of graph is _____
modulus of resilience
in stress-strain graph, total area under graph = ____
toughness (has units of energy)
area under graph energy units
J/m^3
in stress-strain graph, linear slope is ________
modulus of elasticity
