Materials Science Flashcards
7 cards from real Fundamentals of Engineering practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Materials Science flashcards as text
In fatigue failure, crack initiation most commonly occurs at:
Answer: Surface defects, notches, or stress concentrations
Cyclic stress amplification at surface imperfections, machining marks, or geometric discontinuities makes them the preferred sites for fatigue crack initiation.
The endurance limit of a steel refers to:
Answer: The alternating stress amplitude below which fatigue failure will not occur regardless of cycles
Ferrous materials exhibit an endurance limit — a stress amplitude below which the S-N curve becomes horizontal, implying infinite fatigue life.
Galvanic corrosion is driven by:
Answer: Electrical contact between two dissimilar metals in the presence of an electrolyte
When two metals with different electrode potentials are electrically coupled in an electrolyte, the more active (anodic) metal corrodes preferentially.
Creep is defined as:
Answer: Time-dependent plastic deformation under sustained stress at elevated temperature
Creep is slow, time-dependent plastic strain that accumulates under constant stress, becoming significant above roughly 0.4 times the absolute melting temperature.
For a continuous-fiber composite loaded parallel to the fibers, the longitudinal modulus by the rule of mixtures is:
Answer: Ec = Ef·Vf + Em·Vm
In the fiber direction both phases experience the same strain (isostrain), so moduli add in proportion to volume fractions: Ec = Ef·Vf + Em·Vm.
Which fracture mode exhibits significant plastic deformation and produces a dull, fibrous fracture surface?
Answer: Ductile fracture
Ductile fracture involves extensive plasticity, void nucleation and growth, and coalescence, resulting in a dull, fibrous (cup-and-cone in tension) appearance.
Which of the following is NOT a typical reinforcing fiber used in polymer-matrix composites?
Answer: Copper fiber
Carbon, glass, and aramid fibers offer high specific strength and stiffness; copper is too dense and ductile to serve as an effective structural reinforcement fiber.