Chapter 8 Failure Flashcards

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1
Q

What is a simple fracture

A

The separation of a body into two or more pieces

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2
Q

Ductile fracture

A
  • slow crack
  • fails with warning
  • significant plastic deformation
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3
Q

Brittle fracture

A
  • Rapid crack
  • little or no plastic deformation
  • fails without warning
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4
Q

cup and cone fracture vs brittle fracture

A
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5
Q

examples of ductile and brittle fractures

A
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6
Q

5 stages of a moderately ductile failure

A

necking, void nucleation, void growth, crack propagation, fracture

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7
Q

principles of fracture mechanics

A
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8
Q

fracture mechanics formula

A
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9
Q

fracture mechanics, stress concentration formula

A
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10
Q

what is crack propagation

A

a stepwise discontinuous process, which agrees with propagation observed in the field

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11
Q

crack propagation and its criteria

A
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12
Q

what is fracture toughness

A

the measure of a material’s resistance to brittle fracture when a crack is present

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13
Q

fracture toughness formula

A
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14
Q

plane fracture toughness

A
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15
Q

What is the difference between fracture toughness and plane strain fracture toughness?

A

What is the difference between fracture toughness and plane strain fracture toughness?

They are different terms. Toughness is the ability of a material (assumed to be perfect, meaning no cracks) to absorb energy to fracture. It is measured by the area under the stress-strain curve to the point of fracture. Fracture Toughness is the ability of material with pre-cracks to resist fracture by absorbing energy

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16
Q

fracture toughness ranges between

metal alloys

ceramics

polymers

composite fibers

A
17
Q

design against fracture formula and scenarios

A
18
Q

design example aircraft wing

A
19
Q

* quick reference *

Example of brittle fracture of ductile materials

A
20
Q

What is an impact test on ductile materials

A

the amount of energy absorbed by a material during fracture.

21
Q

what influence does T (temp) have on impact energy

A
22
Q

what is fatigue failure

A

is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striations on some parts of the fracture surface.

23
Q

*quick reference *

Fatigue Failure

A
24
Q

two types of fatigue behavior

A

two types of fatigue behavior

Fatigue limit - the highest stress that a material can withstand for an infinite number of cycles without breaking —called also endurance

Fatigue life is defined as the number of cycles that lead to the failure of a structural system

25
Q

* quick reference *

Fatigue behavior

A
26
Q

what are the general techniques for improving fatigue life

A

1) reducing the magnitude of mean stress
2) surface treatments
3) design changes

27
Q

* Improving Fatigue Life *

1) reducing the magnitude of mean stress

A
28
Q

* Improving Fatigue Life *

2) surface treatments

A
29
Q

* Improving Fatigue Life *

3) design changes

A
30
Q

define creep

A

(sometimes called cold flow) is the tendency of a solid material to move slowly or deform permanently under the influence of persistent mechanical stresses.

31
Q

3 stages of creep

A
32
Q

steady-state creep rate formula

A
33
Q

prediction of creep rupture lifetime

A
34
Q

Summary of this chapter

A