EGR 405 - Ch. 7: Mechanical Failures III -
Fatigue Failure questions with accurate answers
A fatigue strength of engineering materials that do not exhibit fatigue or
endurance limit may be equal to how much of their tensile strength?
Ans✓✓✓ 1/3
A large overload indicates what? Ans✓✓✓ The part was heavily
stressed at the time of final fracture
A material's resistance to fatigue is measured with which methods?
Ans✓✓✓ 1. Rotating-beam test
2. Rotating cantilever beam test
A single origin on a fatigue fracture surface usually indicates what?
Ans✓✓✓ low overstress
Concentric marks around the location of the initial flaw showing a
region of slow crack growth. Ans✓✓✓ Progession (beach) marks
Depending on the engineering material and conditions of stress
concentration and stress level, a fatigue fracture surface may include
some or all of what features? Ans✓✓✓ 1. Origin
2. Fatigue slow fracture zone
3. progression or beach marks
4. Striation
,5. Fast fracture zone
6. Ratchet marks
7. River marks
Either high stress or high stress concentrations may cause the prevalence
of what? Ans✓✓✓ Multiple crack origins
Examination of the edges of ratchet marks could reveal what? Ans✓✓✓
Whether torsional forces were involved with the failure
Fatigue at high amplitudes and fatigue lives up to 10^4 cycles is referred
to as what? Ans✓✓✓ Low Cycle Fatigue (High - Level Fatigue)
Fatigue Ans✓✓✓ Failure of a material under a repeatedly applied
stress.
Fatigue Ans✓✓✓ Process whereby cracking occurs under the influence
of repeated or cyclic stresses, which are normally substantially below the
nominal yield strength of the material.
Fatigue cracks tend to show little or no what? Ans✓✓✓ Macroscopic
ductility
Fatigue failure Ans✓✓✓ Dangerous form of fracture, which occurs in
materials when they are subjected to cyclic or otherwise time-variable
load.
, Fatigue Failure Ans✓✓✓ Is responsible for 80 -90% of all structural
and operating failures of machine elements.
Fatigue failures on common in: Ans✓✓✓ a. moving parts (shaft), b.
repeatedly loaded parts (pressure vessels), c. Parts that rotate under load
(axle), d. reciprocating parts under load (connecting rod), e. vibrates
(rotor of helicopter)
Fatigue fractures result from: Ans✓✓✓ The simultaneous action of
repeated or fluctuating cyclic stress, tensile stress, and plastic strain.
Fatigue limit of an engineering material can be increased by doing what
to its strength? Ans✓✓✓ Increasing
Fatigue that covers a large number of cycles, greater than 10^4, is
referred to as what? Ans✓✓✓ High Cycle Fatigue (Low - Level
Fatigue)
Final sudden failure of the remaining cross-section occurs by: Ans✓✓✓
Either shear or brittle fracture
For a given stress amplitude, as the mean stress increases the number of
cycles to fatigue, fatigue life and endurance limit are what? Ans✓✓✓
Decreased substantially
Fatigue Failure questions with accurate answers
A fatigue strength of engineering materials that do not exhibit fatigue or
endurance limit may be equal to how much of their tensile strength?
Ans✓✓✓ 1/3
A large overload indicates what? Ans✓✓✓ The part was heavily
stressed at the time of final fracture
A material's resistance to fatigue is measured with which methods?
Ans✓✓✓ 1. Rotating-beam test
2. Rotating cantilever beam test
A single origin on a fatigue fracture surface usually indicates what?
Ans✓✓✓ low overstress
Concentric marks around the location of the initial flaw showing a
region of slow crack growth. Ans✓✓✓ Progession (beach) marks
Depending on the engineering material and conditions of stress
concentration and stress level, a fatigue fracture surface may include
some or all of what features? Ans✓✓✓ 1. Origin
2. Fatigue slow fracture zone
3. progression or beach marks
4. Striation
,5. Fast fracture zone
6. Ratchet marks
7. River marks
Either high stress or high stress concentrations may cause the prevalence
of what? Ans✓✓✓ Multiple crack origins
Examination of the edges of ratchet marks could reveal what? Ans✓✓✓
Whether torsional forces were involved with the failure
Fatigue at high amplitudes and fatigue lives up to 10^4 cycles is referred
to as what? Ans✓✓✓ Low Cycle Fatigue (High - Level Fatigue)
Fatigue Ans✓✓✓ Failure of a material under a repeatedly applied
stress.
Fatigue Ans✓✓✓ Process whereby cracking occurs under the influence
of repeated or cyclic stresses, which are normally substantially below the
nominal yield strength of the material.
Fatigue cracks tend to show little or no what? Ans✓✓✓ Macroscopic
ductility
Fatigue failure Ans✓✓✓ Dangerous form of fracture, which occurs in
materials when they are subjected to cyclic or otherwise time-variable
load.
, Fatigue Failure Ans✓✓✓ Is responsible for 80 -90% of all structural
and operating failures of machine elements.
Fatigue failures on common in: Ans✓✓✓ a. moving parts (shaft), b.
repeatedly loaded parts (pressure vessels), c. Parts that rotate under load
(axle), d. reciprocating parts under load (connecting rod), e. vibrates
(rotor of helicopter)
Fatigue fractures result from: Ans✓✓✓ The simultaneous action of
repeated or fluctuating cyclic stress, tensile stress, and plastic strain.
Fatigue limit of an engineering material can be increased by doing what
to its strength? Ans✓✓✓ Increasing
Fatigue that covers a large number of cycles, greater than 10^4, is
referred to as what? Ans✓✓✓ High Cycle Fatigue (Low - Level
Fatigue)
Final sudden failure of the remaining cross-section occurs by: Ans✓✓✓
Either shear or brittle fracture
For a given stress amplitude, as the mean stress increases the number of
cycles to fatigue, fatigue life and endurance limit are what? Ans✓✓✓
Decreased substantially
