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

Cyclic stress amplification at surface imperfections, machining marks, or geometric discontinuities makes them the preferred sites for fatigue crack initiation.

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

Ferrous materials exhibit an endurance limit — a stress amplitude below which the S-N curve becomes horizontal, implying infinite fatigue life.

Question 3

Galvanic corrosion is driven by:

Accepted Answer

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

Answer

When two metals with different electrode potentials are electrically coupled in an electrolyte, the more active (anodic) metal corrodes preferentially.

Question 4

Creep is defined as:

Accepted Answer

Time-dependent plastic deformation under sustained stress at elevated temperature

Answer

Creep is slow, time-dependent plastic strain that accumulates under constant stress, becoming significant above roughly 0.4 times the absolute melting temperature.

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

In the fiber direction both phases experience the same strain (isostrain), so moduli add in proportion to volume fractions: Ec = Ef·Vf + Em·Vm.

Fundamentals of Engineering Practice Test

Fundamentals of Engineering Practice Test

Fundamentals of Engineering Materials Science 3