Fracture and Fatigue: Understanding Material Failure

Question 1

Which of the following is NOT a characteristic of brittle fracture?

Accepted Answer

Is accompanied by significant energy absorption

Answer

Occurs with little or no plastic deformation

Answer

Propagates rapidly

Answer

Can be caused by a sharp notch or defect

Question 2

Which of the following is the most common type of ductile fracture?

Accepted Answer

Cup-and-cone fracture

Answer

Shear fracture

Answer

Cleavage fracture

Answer

Intergranular fracture

Question 3

What is the primary difference between static and dynamic fracture?

Accepted Answer

The rate of loading

Answer

The type of material

Answer

The temperature

Answer

The stress state

Question 4

Which of the following is NOT a factor that can contribute to fatigue crack nucleation?

Accepted Answer

Low applied stress

Answer

Surface defects

Answer

Inclusions

Answer

Grain boundaries

Question 5

What is the effect of temperature on fatigue life?

Accepted Answer

It depends on the specific material, loading conditions, and temperature range

Answer

Generally, it decreases with increasing temperature

Answer

Generally, it increases with increasing temperature

Answer

It has no significant effect

Question 6

What is the primary mechanism of failure in a ductile material?

Accepted Answer

Necking

Answer

Cleavage

Answer

Shear

Answer

Tearing

Question 7

What is the relationship between the applied stress intensity factor (K) and the crack length (a) in a brittle material?

Accepted Answer

K is proportional to the square root of a

Answer

K is proportional to a

Answer

K is inversely proportional to the square root of a

Answer

K is inversely proportional to a

Question 8

What is the significance of the fatigue limit?

Accepted Answer

It is the stress level below which fatigue failure will not occur for an infinite number of cycles

Answer

It is the maximum stress that a material can withstand without undergoing fatigue failure

Answer

It is the stress level at which fatigue cracks initiate

Answer

It is not a relevant parameter in fatigue analysis

Question 9

What is the difference in fracture behavior between brittle and ductile materials?

Accepted Answer

Brittle materials fail suddenly with little or no deformation, while ductile materials undergo significant plastic deformation before failure

Answer

Brittle materials have a higher fracture toughness than ductile materials

Answer

Brittle materials are more resistant to fatigue failure than ductile materials

Answer

There is no difference in the fracture behavior of brittle and ductile materials

Question 10

Which type of fracture involves the rapid propagation of a crack through a material with minimal plastic deformation?

Accepted Answer

Brittle fracture

Answer

Ductile fracture

Answer

Fatigue fracture

Answer

Creep fracture

Question 11

What is the fundamental difference between ductile and brittle fracture?

Accepted Answer

Ductile fracture involves plastic deformation, while brittle fracture does not

Answer

Brittle fracture involves plastic deformation, while ductile fracture does not

Answer

They are both types of fatigue failure

Answer

They have the same failure mechanisms

Question 12

How are fracture toughness and fracture strength related?

Accepted Answer

Fracture toughness measures the resistance to crack propagation, while fracture strength is the maximum stress a material can withstand before fracturing

Answer

Fracture strength measures the resistance to crack propagation, while fracture toughness is the maximum stress a material can withstand before fracturing

Answer

They are both measures of a material's resistance to fracture

Answer

They are not related

Question 13

What is the significance of the Paris law in fatigue analysis?

Accepted Answer

It is an empirical relationship that describes the growth rate of fatigue cracks

Answer

It provides a theoretical framework for predicting fatigue life

Answer

It is a tool for experimentally measuring fracture toughness

Answer

It is a design code used to prevent fatigue failure

Question 14

Which characteristic is NOT associated with brittle fracture?

Accepted Answer

Cup and cone fracture surface

Answer

Low energy absorption

Answer

Rapid crack propagation

Answer

Little or no plastic deformation

Question 15

Fatigue failure is a result of:

Accepted Answer

Cyclic loads below the yield strength

Answer

High static loads

Answer

Impact loads

Answer

Creep loads

Question 16

A typical fracture toughness specimen has the shape of:

Accepted Answer

Compact tension

Answer

Tensile

Answer

Charpy V-notch

Answer

Izod

Question 17

The Paris law for fatigue crack growth relates:

Accepted Answer

Crack growth rate to stress intensity factor range

Answer

Fatigue life to stress amplitude

Answer

Fracture toughness to crack length

Answer

Yield strength to strain rate

Question 18

Brittle fracture is characterized by:

Accepted Answer

Sudden failure with little or no plastic deformation

Answer

Progressive crack growth

Answer

Large plastic deformation

Answer

High fracture toughness

Question 19

Fatigue failure is characterized by:

Accepted Answer

Progressive crack growth

Answer

Sudden failure

Answer

Large plastic deformation

Answer

High fracture toughness

Question 20

The primary mechanism of ductile fracture is:

Accepted Answer

Microvoid coalescence

Answer

Cleavage

Answer

Shear banding

Answer

Grain boundary cavitation

Question 21

The relationship between crack length and stress intensity factor is:

Accepted Answer

Square root

Answer

Linear

Answer

Exponential

Answer

Inversely proportional

Question 22

Precipitates play a role in fatigue crack initiation by:

Accepted Answer

Acting as crack nucleation sites

Answer

Strengthening the material

Answer

Reducing the stress concentration

Answer

Increasing the fracture toughness

Question 23

The purpose of a fracture toughness test is to:

Accepted Answer

Determine the critical stress intensity factor for a material

Answer

Predict the fatigue life of a component

Answer

Identify the type of fracture that is likely to occur

Answer

Measure the strength of a material

Question 24

Which of the following factors does not influence the brittle fracture of a material?

Accepted Answer

Shear stress

Answer

Temperature

Answer

Grain size

Answer

Strain rate

Question 25

What type of fracture occurs when a material fails abruptly with limited plastic deformation and exhibits a rough, irregular fracture surface?

Accepted Answer

Brittle fracture

Answer

Ductile fracture

Answer

Fatigue fracture

Answer

Creep fracture

Question 26

Which mechanism is primarily responsible for fatigue failure in materials?

Accepted Answer

Crack initiation and propagation

Answer

Dislocation motion

Answer

Grain boundary sliding

Answer

Void formation and coalescence

Question 27

What is the primary significance of the fracture toughness of a material?

Accepted Answer

Resistance to crack propagation

Answer

Tensile strength

Answer

Elastic modulus

Answer

Yield strength

Question 28

In a notched specimen subjected to tensile loading, what type of fracture is most likely to occur at the notch tip?

Accepted Answer

Brittle fracture

Answer

Ductile fracture

Answer

Fatigue fracture

Answer

Viscous fracture

Question 29

Which stress state is most likely to cause fatigue failure in metallic materials?

Accepted Answer

Tensile

Answer

Compressive

Answer

Shear

Answer

Hydrostatic

Question 30

The S-N curve represents:

Accepted Answer

Stress amplitude vs. number of cycles to failure

Answer

Strain amplitude vs. number of cycles to failure

Answer

Fatigue strength vs. temperature

Answer

Crack length vs. time

Question 31

The Griffith criterion for fracture states that:

Accepted Answer

The critical stress intensity factor is equal to the square root of the critical strain energy release rate

Answer

The critical fracture toughness is equal to twice the critical J-integral

Answer

The critical crack length is equal to the critical stress intensity factor divided by the elastic modulus

Answer

The critical J-integral is equal to the critical stress intensity factor squared divided by the elastic modulus

Question 32

The primary mechanism of fatigue crack growth involves:

Accepted Answer

Slip band formation and coalescence

Answer

Void nucleation and growth

Answer

Dislocation pile-up and crack extension

Answer

Atomic diffusion and creep

Question 33

Which of the following is NOT a common type of fracture?

Accepted Answer

Plastic fracture

Answer

Brittle fracture

Answer

Ductile fracture

Answer

Fatigue failure

Question 34

What is the primary mechanism of ductile fracture in metals?

Accepted Answer

Void coalescence

Answer

Grain boundary cracking

Answer

Neck formation

Answer

Cleavage

Question 35

Which of the following is a common test method used to evaluate a material's fracture toughness?

Accepted Answer

Three-point bending test

Answer

Tensile test

Answer

Charpy impact test

Answer

Rockwell hardness test

Question 36

Which of the following is a distinctive feature of ductile fractures?

Accepted Answer

Extensive plastic deformation

Answer

Sharp, jagged edges

Answer

Minimal energy absorption during fracture

Answer

Crack propagation along grain boundaries

Question 37

What is the primary driving force behind crack growth during fatigue failure?

Accepted Answer

Stress concentration at the crack tip

Answer

Plastic deformation around the crack tip

Answer

Corrosion along grain boundaries

Answer

Hydrogen embrittlement

Question 38

How do the fracture surfaces of brittle and ductile materials differ?

Accepted Answer

Brittle fractures display cleavage planes, while ductile fractures exhibit shear lips

Answer

Brittle fractures exhibit a rough, fibrous texture, while ductile fractures have a smooth, crystalline appearance

Answer

Ductile fractures exhibit a rough, fibrous texture, while brittle fractures have a smooth, crystalline appearance

Answer

Ductile fractures display cleavage planes, while brittle fractures exhibit shear lips

Question 39

What is the primary purpose of fracture toughness testing?

Accepted Answer

To assess the material's resistance to brittle fracture

Answer

To predict the fatigue life of a component

Answer

To quantify the plastic zone size at a crack tip

Answer

To evaluate the effectiveness of fracture prevention techniques

Question 40

Which of the following is NOT a mechanism of brittle fracture?

Accepted Answer

Ductile fracture

Answer

Cleavage

Answer

Microvoid coalescence

Answer

Grain boundary fracture

Question 41

What is the critical stress intensity factor?

Accepted Answer

The stress required to propagate a crack

Answer

The stress required to initiate a crack

Answer

The stress at the tip of a crack

Answer

The stress at the yield point

Question 42

Which of the following factors does NOT affect fatigue life?

Accepted Answer

Humidity

Answer

Stress amplitude

Answer

Frequency

Answer

Material microstructure

Question 43

What is the Griffith criterion for crack propagation?

Accepted Answer

A crack will propagate if the energy released by crack growth is greater than the energy required to create new crack surfaces.

Answer

A crack will propagate if the stress intensity factor is greater than the critical stress intensity factor.

Answer

A crack will propagate if the strain energy release rate is greater than the critical strain energy release rate.

Answer

A crack will propagate if the plastic zone size is greater than the crack length.

Question 44

Which of the following is NOT a type of fatigue loading?

Accepted Answer

Impact loading

Answer

Constant amplitude loading

Answer

Variable amplitude loading

Answer

Random loading

Question 45

Which of the following is a method to prevent fatigue failure?

Accepted Answer

Shot peening

Answer

Annealing

Answer

Quenching

Answer

Tempering

Question 46

What is the S-N curve?

Accepted Answer

A plot of fatigue life versus stress amplitude

Answer

A plot of fatigue life versus frequency

Answer

A plot of fatigue life versus temperature

Answer

A plot of fatigue life versus load ratio

Question 47

What is the primary mechanism responsible for fatigue crack propagation?

Accepted Answer

Slip and dislocation motion

Answer

Twinning and deformation banding

Answer

Grain boundary sliding

Answer

Stress corrosion cracking

Question 48

Which of the following is a characteristic of ductile fracture **(as opposed to brittle fracture)**?

Accepted Answer

Significant plastic deformation

Answer

Rapid crack propagation

Answer

Low energy absorption

Answer

Smooth fracture surface

Question 49

What is the primary purpose of the Paris law equation?

Accepted Answer

To describe fatigue crack growth rate

Answer

To predict catastrophic failure

Answer

To predict fatigue life

Answer

To predict the toughness of a material

Question 50

Which of the following microstructures is generally **more susceptible** to brittle fracture?

Accepted Answer

BCC with high carbon content

Answer

FCC with fine grain size

Answer

HCP with low stacking fault energy

Answer

Amorphous

Question 51

What is the significance of the yield strength in fatigue failure?

Accepted Answer

It influences the fatigue crack growth rate

Answer

It determines the fatigue limit of the material

Answer

It has no significant effect on fatigue behavior

Answer

It determines the toughness of the material

Question 52

Identify the primary mechanism responsible for fatigue failure.

Accepted Answer

Cyclic loading

Answer

Creep

Answer

Impact loading

Answer

Overheating

Question 53

Which factor does NOT influence the fatigue life of a material?

Accepted Answer

Magnetic field

Answer

Stress concentration

Answer

Material properties

Answer

Loading frequency

Question 54

What is the primary purpose of a fracture toughness test?

Accepted Answer

Determine a material's resistance to crack propagation

Answer

Measure the material's yield strength

Answer

Predict the service life of a component

Answer

Assess the material's ductility

Question 55

Which factor does NOT affect the fatigue strength of a material?

Accepted Answer

Magnetic field

Answer

Surface finish

Answer

Temperature

Answer

Corrosion

Question 56

What is the key difference in fracture behavior between ductile and brittle materials?

Accepted Answer

Ductile materials exhibit significant plastic deformation before fracture, unlike brittle materials.

Answer

Brittle materials exhibit significant plastic deformation before fracture, unlike ductile materials.

Answer

Ductile materials fracture along a smooth surface, while brittle materials fracture along a jagged surface.

Answer

Brittle materials fracture along a smooth surface, while ductile materials fracture along a jagged surface.

Question 57

What is the Griffith criterion for brittle fracture?

Accepted Answer

The critical stress intensity factor is reached, causing rapid crack propagation

Answer

The fracture toughness is greater than the critical stress intensity factor

Answer

The yield strength of the material is exceeded

Answer

The material exhibits a high ductility

Question 58

Which of the following materials is known for its exceptional fatigue strength?

Accepted Answer

Titanium

Answer

Steel

Answer

Aluminum

Answer

Ceramics

Question 59

What is the purpose of shot peening in fatigue life improvement?

Accepted Answer

It induces compressive residual stresses on the surface

Answer

It increases the material's yield strength

Answer

It reduces the number of surface defects

Answer

It improves the material's corrosion resistance