
Which material criterion should used to minimize the mass for a given beam stiffness?
Maximize E/p

Suppose the price per kilogram of material is denoted by C_{m}. Which criterion should be used to minimize the price for a given beam stiffness?
Maximize E/C_{m}p

Equation for stiffness
F/(displacement)

What kind of loading causes buckling to occur?
Compression

Which factor from equation F_{crit}=(n^{2}pi^{2}EI)/L^{2} depends on the shape of a structural member and the square of its crosssectional area?
I

Which kinds of structural members are most susceptible to buckling?
long columns

If the geometry of the beam or plate is held constant, how does the vibrational frequency scale with material properties?
f=(E/p)^{1/2}

A hard diamond indenter is pressed into the surface of a material with force F, creating a permanent indentation of depth l and area A. Suppose the material has modulus E, shear modulus G, and strength sigma. How is the hardness computed from this test?
F/A

According to the text, what is the approximate relationship between hardness and yield strength for many materials?
H=3(yield strength)

The tensile strain at fracture is a measure of which property?
Ductility

Where does the largest shear stress occur in s sample subjected to a tensile load?
Planes inclined at 45 to the tensile load

What drives dislocation glide?
Shear stress

What are four ways to strengthen a metal?
 1. dispersion of small particles
 2. introduction of solutes
 3. reduction of grain size
 4. plastic deformation

What are four ways to strengthen a polymer?
 reinforcement of fibers like glass
 blending with stronger polymer
 crosslinking
 drawing

How is workhardening explained?
Dislocations obstruct each other

What is intrinsic strength?
Strong atomic bonds resist dislocation movement

How is solid solution hardening explained?
Solutegenerated stresses "roughen" slip planes

How is dispersion strengthening explained?
Precipitates obstruct dislocation movement

What occurs during elastic deformation?
Atomic bonds stretch but do not break

What is annealing?
Heating removes dislocations

What is cold working of a metal?
Plastic deformation without heating

How can workhardening be reversed?
Annealing

What causes many materials to yield at stresses far below their ideal strength?
dislocations

What is an edge dislocation?
An extra half plane of atoms

What is a glide plane?
Plane which a dislocation moves

Identify each of the quantities in following equation:
Y(sigma)(pi*c)^{1/2}=(EG_{c})^{1/2}
 Y=correction factor
 sigma=nominal stress
 c=crack length
 G_{c}=toughness
 E=elastic modulus
 (EG_{c})^{1/2}=fracture toughness

Which phenomenon does Y(sigma)(pi*c)^{1/2}=(EG_{c})^{1/2} describe?
Fast fracture

What causes brittle fracture?
long, sharptipped cracks

What can happen at the tip of a crack when local stress exceeds the ideal strength?
Crack propagates by cleavage

What can happen at the tip of a crack when local stress exceeds the yield strength?
Plastic deformation that blunts the crack tip

How does ductile fracture occur?
Linking of voids in plastic zone

How can the addition of glass fiers to a polymer matrix crate a tough composite?
Gibers act as crack stoppers

Why are many ductile materials also quite tough?
Energy is consumed by plastic flow

How do cracks start in an uncracked component subject to highcycle fatigue?
Local plasticity occurs where scratches or section changes concentrate stess

How do cracks start in an uncracked component subject to lowcycle fatigue?
General plasticity roughens the surface

What happens during peening?
Residual surface compressive stresses are introduced

What causes workhardening?
Dislocations accumulate and hinder each other

What happens during cyclic loading when K_{max}=K_{1c}?
Fails by fast fracture

In the context of this course, what is fatigue?
Failure of a structure due to cyclic stress

Which process(es) can cause the formation and slow growth of cracks at loads well below the yield strength?
Corrosion

Which process generally causes final failure in fatigue?
Fast fracture

What is the cyclic stress intensity range, delta(K)?
K_{max}K_{min} or Y(delta(sigma))(pi*c)^{1/2}

What is the definition of the mean stress?
(sigma_{max}+sigma_{min})/2

What is the definition of the stress amplitude?
(Sigma_{max}sigma_{min})/2

What is the definition of the cyclic stress range?
sigma_{max}sigma_{min}

