Unit 8 - Fatigue

Question 1

4 things the magnitude of K depends on

Answer 1

sample geometry
size and location of the crack
magnitude of load
distribution of load

Question 2

types of fatigue

Answer 2

un-cracked have high cycle and low cycle fatigue

cracked structure

Question 3

define fatigue strength

Answer 3

the cyclic stress range for which failure will occur after N cycles

Question 4

define fatigue life

Answer 4

is the expected number of cycles to failure for a given stress range

Question 5

endurance limit

Answer 5

is the maximum stress range that can be applied without causing failure

Question 6

5 things the evolution of an S = N curve will be affected by

Answer 6

stress magnitude
corrosion
temperature
residual stress
magnitude of defects

Question 7

three phases of fatigue failure

Answer 7

crack initiation: formation of small crack at stress concentration or surface defect of crack length half-a
crack propagation: crack length increases slowly and incrementally with each stress cycle. increasing crack length increases stress intensity factor and increases crack propagation rate
final failure: occurs hen crack size is so large