Fundamentals of Engineering Materials Science 3

Question 1

In fatigue failure, crack initiation most commonly occurs at:

Accepted Answer

Surface defects, notches, or stress concentrations

Answer

The geometric center of the cross-section

Answer

Uniformly distributed grain boundaries

Answer

Regions of maximum compressive stress

Question 2

The endurance limit of a steel refers to:

Accepted Answer

The alternating stress amplitude below which fatigue failure will not occur regardless of cycles

Answer

The maximum static stress the material can sustain

Answer

The temperature above which creep deformation becomes significant

Answer

The maximum achievable hardness after quenching

Question 3

Galvanic corrosion is driven by:

Accepted Answer

Electrical contact between two dissimilar metals in the presence of an electrolyte

Answer

Exposure of a single metal to high-temperature oxidizing gases

Answer

Uniform surface oxidation of a metal exposed to ambient air

Answer

Hydrogen embrittlement at high-stress sites

Question 4

Creep is defined as:

Accepted Answer

Time-dependent plastic deformation under sustained stress at elevated temperature

Answer

Sudden brittle fracture under impact loading

Answer

Instantaneous elastic deformation that fully recovers when load is removed

Answer

Progressive surface wear due to sliding contact

Question 5

For a continuous-fiber composite loaded parallel to the fibers, the longitudinal modulus by the rule of mixtures is:

Accepted Answer

Ec = Ef·Vf + Em·Vm

Answer

Ec = Ef·Vm + Em·Vf

Answer

1/Ec = Vf/Ef + Vm/Em

Answer

Ec = (Ef·Em)/(Ef·Vm + Em·Vf)

Question 6

Which fracture mode exhibits significant plastic deformation and produces a dull, fibrous fracture surface?

Accepted Answer

Ductile fracture

Answer

Brittle cleavage fracture

Answer

Intergranular fracture

Answer

Stress-corrosion cracking

Question 7

Which of the following is NOT a typical reinforcing fiber used in polymer-matrix composites?

Accepted Answer

Copper fiber

Answer

Carbon (graphite) fiber

Answer

E-glass fiber

Answer

Aramid (Kevlar) fiber