Week 2: Mechanical Properties

Question 1

classification of mechanical properties

Answer 1

1st classifications: bulk/surface

2nd classifications: sub-classifications of bulk properties (fundamental, applied)

Question 2

force per unit area from externally applied forces

Answer 2

stress

Question 3

unit of stress

Answer 3

Pa/MPa

Question 4

fundamental types of stress

Answer 4

tension, compression, shear

Question 5

force perpendicular to resisting area

Answer 5

tension

Question 6

force perpendicular to resisting area, sense of load opposite to that of tension

Answer 6

compression

Question 7

force parallel to resisting area

Answer 7

shear

Question 8

combined types of stress

Answer 8

torsion, flexure/bending

Question 9

where does stress concentrate?

Answer 9

notches, grooves, cracks, surface irregularities

Question 10

describes relative deformation or change in shape and size with respect to initial length under applied forces (stresses)

Answer 10

strain

Question 11

strain that is recoverable

Answer 11

elastic

Question 12

strain that is permanent

Answer 12

plastic

Question 13

high modulus equals what type of material?

Answer 13

rigid material

Question 14

low modulus equals what type of material?

Answer 14

less rigid material

Question 15

Stresses _______ than the

elastic limit produce permanent/plastic deformation in the material.

Answer 15

equal to or higher

Question 16

Stress at which material changes from elastic to plastic strain

Answer 16

elastic

Question 17

ductility/malleability is measured by what

Answer 17

% of elongation

Question 18

high % ductility/malleability equals what?

Answer 18

ductile material

Question 19

low % ductility/malleability equals what?

Answer 19

brittle material

Question 20

stress at which material breaks, last point in stress-strain curve

Answer 20

Ultimate Tensile Strength (UTS)

Question 21

Maximum stress the material undergoes during stress-strain test

Answer 21

maximum stress

Question 22

Amount of energy a material can absorb without permanently deforming

Answer 22

resilience

Question 23

Total amount of energy a material can absorb until fracture

Answer 23

toughness

Question 24

ability for material to resist indentations, resistance to be scratched

Answer 24

hardness

Question 25

loss of anatomic form from surface or restoration, results in wear

Answer 25

abrasion

Question 26

Repeated low forces (below elastic limit) that bring the material to an unexpected fracture

Answer 26

fatigue stress

Question 27

a key note about viscoelasticity, or combination of viscous and elastic behavior, is that it is __ _____

Answer 27

time dependent

Question 28

slow deformation with time under constant stress

Answer 28

creep

Question 29

material constantly deformed, may show drop in stress to keep deformation with time

Answer 29

stress relaxation

Question 30

laboratory tests (__ _____) ____ predict ___ ______ behavior

Answer 30

in vitro, cannot, in vivo

Question 31

consideration of the whole mass of material

Answer 31

bulk properties

Question 32

examples of bulk properties

Answer 32

strength, elasticity, etc.

Question 33

examples of surface properties

Answer 33

hardness, wear, etc.

Question 34

sub-classification of bulk properties

Answer 34

fundamental properties, applied properties

Question 35

stress is applied from...

Answer 35

external forces

Question 36

calculations of stress

Answer 36

Force (F) / cross-sectional area (A)

Question 37

strain is...

Answer 37

dimensionless

Question 38

in stress-stain graph... y axis = x axis =

Answer 38

y axis = stress AND strength | x axis = strain

Question 39

area under curve of stress-strain graph is...

Answer 39

values of force per displacement (work)

Question 40

linear part of the graph is...

Answer 40

elastic strains

Question 41

flexibility (is/is not) a fundamental property

Answer 41

is NOT

Question 42

change from elastic to plastic strain points

Answer 42

"PEY" proportional limit elastic limit yield point

Question 43

if you go above ___ ____, restorations will fail

Answer 43

elastic limit

Question 44

maximum strength is found at the _______

Answer 44

highest point of the graph

Question 45

malleability: ability of a material to be formed into a ____

Answer 45

sheet

Question 46

ductility: ability of a material to be formed into a ____

Answer 46

wire

Question 47

in stress-strain graph, area underneath linear slope of graph is _____

Answer 47

modulus of resilience

Question 48

in stress-strain graph, total area under graph = ____

Answer 48

toughness (has units of energy)

Question 49

area under graph energy units

Answer 49

J/m^3

Question 50

in stress-strain graph, linear slope is ________

Answer 50

modulus of elasticity