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Flashcards in Dent 1.1 Deck (33):
1

how is stress measured

Ratio of force per area (or stress)

2

Tension

Elongation forces directed away from each other in the same straight line (molecules resist being pulled apart)

3

Compression

shrinkage forces directed toward eachother in the same straight line (molecules resist being forced more closely together)

4

Shear

Forces paralle NOT along the same straight line (one portion resists sliding past the other

5

Torsion

twisting forces

6

Bending

results from a bending moment

7

Define strain

Deformation caused by stress

8

what is the proportional limit

The greatest sustained stress with out deviation from the linear proportionality of the stress strains

9

at what point does irreversible stain occur, and what is this region called

Once the Curve is no longer linear, Plastic region

10

what is the Elastic Limit

The greatest stress sustained without permanent deformation

11

when would Proportional limit and elastic limit represent the same stress within the same structure

In Linearly Elastic Materials

12

the stress at which the material begins to function in a plastic manner (permanent strain of about 0.2%)

yield strength

13

_____ _____ is slightly higher then _____ _____ because it include a slight amount of permanent deformation.

Yield strength, proportional limit

14

what are the two types of permanent defomration

Destructive - filling, crowns ect.
Constructive - ortho wires, partial clasps

15

Ultimate strength

The Highest point on the graph, the stress that a material can withstand.

16

which is more important, Yield strenght of Ultimate strength

Yield strength

17

Fracture strength

stress at which a brittle material fractures

18

for most dental alloys and ceramics subjected to tension, , the US and Sf will be _______

Similar

19

Elongation

Deformation that results from the application of tensile force, indicates the workability of alloy

20

Elastic modulus

the measure of elastisity, represents the stiffness of the material with in the elastic region. E=stress/strain

21

The _____ the value of E, the more stiff or rigid the material

Higher

22

resistance of material to permanent deformation is known as

Resilience (the area under the Elastic portion)

23

the resistance of material to fracture

Toughness

24

the combination of what three things increases toughness

combination of
yield strength
Ultimate strength
Strain

25

what are fracture Mechanics

Characterizes the behavior of materials with cracks or flaws

26

what is used to measure the strength of brittle materials

Diametral compression test

27

fatugue strength

the stress at which the material fails under repeated loading

28

endurance limit

stress at which the material can be loaded an infunuite number of times with out failing

29

fatigue depends on the ______ of the load and the ________ of loadings

Magnitude, Number

30

materials with mechanical properties dependant on loading rate are termed

Viscoelastic

31

the resistance of a fluid to flow

Viscosity

32

CREEP

increase in strain in material under constant stress

33

resistance to tearing forces are known as

Tear strength