Fatigue Loading - ANSWER Occurs when a structure experiences dynamic,
fluctuating or variable loads
Fatigue - ANSWER an issue in any structure that is subjected to variable
loading (mechanical, pressure, or thermal); often the cause of many structure
failures
Fatigue Failure - ANSWER occurs due to excessive dynamic, repeated,
fluctuating or variable loading
What is a frequent cause of catastrophic failures? Why? - ANSWER Fatigue
Loading; it is poorly understood and difficult to predict
Where do fatigue failures occur? - ANSWER Typically at stress levels
significantly lower that the yield strengths of the materials. Using static failure
theories can lead to unsafe designs when loads are dynamic
What are the two categories of fatigue? - ANSWER Low cycle
High cycle
Fatigue is caused by... - ANSWER Bending, torsional, axial, combined,
thermal, and pressure loads
Plastic Strain - ANSWER occurs when the stress at the discontinuity exceeds
the elastic limit
Material that exhibit a decreasing elastic limit - ANSWER Cold Drawn Steel
Material that exhibit an increasing elastic limit - ANSWER Annealed Steel
Coffin- Manson Relationship - ANSWER the sum of the elastic and plastic
strain amplitudes (total strain amplitude); the relationship between fatigue life
and total strain amplitude
, What do S-N curves represent? - ANSWER average lifetime versus stress
level
An unfinished rolled or forged element may _________________ or less of the
same part which has been ground and polished - ANSWER have half the
fatigue strength
Surface Factor Formula - ANSWER Cf=aSut^b
Impact - ANSWER a load applied suddenly which creates greater stresses in
any application than an equal load applied gradually
The size factor, Cs, for axial loading - ANSWER there is no size effect,
therefore Cs = 1
Brittle Fracture - ANSWER A strong possibility when operating temperatures
are below room temperatures and should be investigated first under these
circumstances
Yield - ANSWER should be investigates first when the operating temperature
is higher than room temperature; Yield strength drops off rapidly with increased
temperature
Creep - ANSWER will be induced in a material operating at high temperatures
Endurance limit for steels increases slightly...... - ANSWER when the
operating temperature rises to 400F and then begins to decrease in the 400-700
F range
Fatigue Stress Concentration Factor - ANSWER must be used when designing
against fatigue
When can you not used a Fatigue Stress Concentration Factor? - ANSWER In
ductile materials or materials that act as if they are ductile
Notch Sensitivity - ANSWER a measure of how a material reacts due to the
presence of a notch
fluctuating or variable loads
Fatigue - ANSWER an issue in any structure that is subjected to variable
loading (mechanical, pressure, or thermal); often the cause of many structure
failures
Fatigue Failure - ANSWER occurs due to excessive dynamic, repeated,
fluctuating or variable loading
What is a frequent cause of catastrophic failures? Why? - ANSWER Fatigue
Loading; it is poorly understood and difficult to predict
Where do fatigue failures occur? - ANSWER Typically at stress levels
significantly lower that the yield strengths of the materials. Using static failure
theories can lead to unsafe designs when loads are dynamic
What are the two categories of fatigue? - ANSWER Low cycle
High cycle
Fatigue is caused by... - ANSWER Bending, torsional, axial, combined,
thermal, and pressure loads
Plastic Strain - ANSWER occurs when the stress at the discontinuity exceeds
the elastic limit
Material that exhibit a decreasing elastic limit - ANSWER Cold Drawn Steel
Material that exhibit an increasing elastic limit - ANSWER Annealed Steel
Coffin- Manson Relationship - ANSWER the sum of the elastic and plastic
strain amplitudes (total strain amplitude); the relationship between fatigue life
and total strain amplitude
, What do S-N curves represent? - ANSWER average lifetime versus stress
level
An unfinished rolled or forged element may _________________ or less of the
same part which has been ground and polished - ANSWER have half the
fatigue strength
Surface Factor Formula - ANSWER Cf=aSut^b
Impact - ANSWER a load applied suddenly which creates greater stresses in
any application than an equal load applied gradually
The size factor, Cs, for axial loading - ANSWER there is no size effect,
therefore Cs = 1
Brittle Fracture - ANSWER A strong possibility when operating temperatures
are below room temperatures and should be investigated first under these
circumstances
Yield - ANSWER should be investigates first when the operating temperature
is higher than room temperature; Yield strength drops off rapidly with increased
temperature
Creep - ANSWER will be induced in a material operating at high temperatures
Endurance limit for steels increases slightly...... - ANSWER when the
operating temperature rises to 400F and then begins to decrease in the 400-700
F range
Fatigue Stress Concentration Factor - ANSWER must be used when designing
against fatigue
When can you not used a Fatigue Stress Concentration Factor? - ANSWER In
ductile materials or materials that act as if they are ductile
Notch Sensitivity - ANSWER a measure of how a material reacts due to the
presence of a notch
