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Flashcards in Fatigue 1 Deck (5)
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1
Q

What is fatigue?

A
  • Failure of a component after repeated loading at levels lower than the static failure load.
  • Approx. 90% of metallic failures are due to fatigue.
  • Fatigue failure occurs suddenly (a > ac) and is brittle-like in nature.
2
Q

What are the stages of fatigue?

A

(1) Crack initiation: a small crack forms at some point of high stress
concentration (e.g. scratches, dents, threads)
(2) Crack propagation: crack advances incrementally with each stress cycle
(3) Final failure: occurs very rapidly once the crack has reached a critical
size.
Cyclic loading, to microstructural surface discontinuities, to microscopic cracks, to coalescence of micro cracks into a big crack (striations), to stable crack growth (beach marks), therefore rapid failure

3
Q

What is fatigue/ endurance limit?

A

the largest value of repeated stress that will not cause failure for an infinite number of
cycles.

4
Q

What is fatigue strength?

A

the stress level at which failure will occur for some

specified number of cycles

5
Q

What is fatigue life?

A

number of cycles to cause failure at a specified stress level