Failure Analysis & Prevention Flashcards
7 cards from real CFS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Failure Analysis & Prevention flashcards as text
Which environmental condition most accelerates galvanic corrosion between steel fasteners and aluminum structural members?
Answer: Presence of an electrolyte such as saltwater
Galvanic corrosion requires an electrolyte to conduct ionic current; saltwater dramatically increases conductivity and accelerates the corrosion cell between dissimilar metals.
What is the primary purpose of performing a torque audit on in-service fasteners?
Answer: To detect loss of preload and potential loosening
A torque audit checks whether fasteners still have adequate clamp load by measuring the torque required to continue turning them, revealing any relaxation or loosening.
Fretting wear on fastener contact surfaces is characterized by:
Answer: Red-brown iron oxide debris and surface pitting
Fretting produces fine metallic debris that oxidizes to form characteristic red-brown iron oxide powder, along with surface pitting at the contact interface.
A fastener assembly in a chemical plant fails due to dealloying. Which alloy is most susceptible to dezincification?
Answer: Yellow brass (Cu-Zn)
Brass (copper-zinc alloys) is highly susceptible to dezincification, where zinc is selectively leached, leaving a weak, porous copper structure.
During failure analysis, scanning electron microscopy (SEM) is primarily used to:
Answer: Examine fracture surface morphology at high magnification
SEM provides high-magnification, high-depth-of-field images of fracture surfaces, enabling identification of fatigue striations, intergranular patterns, and other failure signatures.
What thread form defect most significantly reduces a fastener's fatigue life?
Answer: Sharp thread root radius (under-radius)
A sharp or undersized thread root radius creates a severe stress concentration, dramatically reducing fatigue life since cracks typically initiate at the first thread root.
Which proof load test result indicates a fastener has undergone permanent set and should be rejected?
Answer: Fastener elongates 0.0005 in. permanently after load removal
A fastener that does not return to its original length after proof load removal has undergone permanent set, indicating the material yielded and the part fails the proof load requirement.