Fatigue and Stress | Metal Fatigue

Question 1

Ultimate stress is where the metal will ___ after applying a ___

Answer 1

fracture, single load

Question 2

Repeated loads well below the level of ultimate stress will eventually have a similar effect, called metal ___

Answer 2

fatigue

Question 3

___ ___ is the initiation and propagation of microscopic cracks, due to the slippage of atomic planes within a metal component

Answer 3

Metal fatigue

Question 4

An applied load only needs to be around __% of the ultimate load or stress for a fatigue crack to occur.

Answer 4

30

Question 5

Fatigue cycles are ___ and ___ ____

Answer 5

cumulative non reversible

Question 6

The most significant factors are:

Answer 6

• Type of operation
• Magnitude and frequency of loads
• Quality of material

Question 7

Composite materials, fatigue is not a consideration at stress cycle around __% of the ultimate stress, because the individual elements tend to fail rather than the structure itself

Answer 7

80

Question 8

Compared to metal, composite structures weaken ___

Answer 8

gradually

Question 9

The local stress at any round hole in a sheet of metal under tension is _ times the average

Answer 9

3

Question 10

Fatigue cracks have 3 stages, which are:

Answer 10

• Initiation
• Growth
• Final Fracture

Question 11

Corrosion helps a crack grow ___

Answer 11

faster

Question 12

Stop drilling is __

Answer 12

drilling a small hole at the end of the crack to stop it spreading.

Question 13

Weak points can be reduced by using ____ instead of rivets and bolts and by casting wing skins in large panels

Answer 13

adhesives

Question 14

Airworthiness can be extended if 4 golden rules are followed:

Answer 14

• Accurate records
• Stay with limitations of flight manual
• Do not use wrong parts
• Report exceedances

Question 15

Corrosion can occur when dissimilar metals are used together and one of them breaks down into various compounds, either by ___ or ___ action

Answer 15

chemical or electrolytic

Question 16

Corrosion worsens with ___ temperature and ___ humidity

Answer 16

increased increased

Question 17

When steel is mixed with aluminium, you will get ___ corrosion after moisture acts as an electrolyte.

Answer 17

galvanic

Question 18

Corrosion can be prevented with ___ based, or by ___ ___ the panels

Answer 18

zinc, electrically isolating

Question 19

Steel terminals should be ___ plated if you want to use them with copper cabling

Answer 19

cadmium

Question 20

Copper and cadmium are relatively ___ in terms of electrical potential

Answer 20

close

Question 21

Aluminium and magnesium will corrode ___ because they ___ in terms of electrical potential

Answer 21

easily far

Question 22

Oxidation is the loss of at least ___ electron(s) when two or more substances interact, which may or may not include oxygen

Answer 22

one

Question 23

Oxygen is very caustic with ___

Answer 23

iron

Question 24

With copper, a ___ ___ of copper oxide will form

Answer 24

greenish layer

Question 25

Destructive oxidation cannot occur if the oxygen cannot penetrate a surface to reach the ___ ___ it craves

Answer 25

free radicals

Question 26

Stress Corrosion Cracking is the unexpected failure of normally ductile metals subjected to ___ __ in a corrosive environment, especially at ___ temperatures

Answer 26

tensile stress, higher

Question 27

SSC is caused by ___

Answer 27

chemicals

Question 28

The chemicals that can cause SSC will make the metal look ___ ____ ____

Answer 28

bright and shiny

Question 29

SSC progresses ___

Answer 29

rapidly

Question 30

SSC is more common among ___ than pure metals

Answer 30

alloys