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 failure mode occurs when a fastener breaks perpendicular to its axis due to repeated cyclic loading?
Answer: Transverse fatigue fracture
Transverse fatigue fractures are perpendicular to the fastener axis and result from cyclic tensile loading exceeding the endurance limit.
A fastener in a marine environment fails with a brittle, branching crack pattern. What is the most likely failure mechanism?
Answer: Stress corrosion cracking
Stress corrosion cracking (SCC) produces branching, intergranular cracks in susceptible alloys exposed to aggressive environments like seawater.
What does the presence of 'beach marks' (arrest lines) on a fracture surface indicate?
Answer: Fatigue crack propagation
Beach marks are macroscopic concentric lines on a fracture surface that indicate incremental fatigue crack growth during cyclic loading.
A grade 8 bolt fails shortly after installation with no apparent overload. It shows a brittle, intergranular fracture with no plastic deformation. What is the most probable cause?
Answer: Hydrogen embrittlement from plating
Hydrogen embrittlement from electroplating (if not properly baked) is a classic cause of delayed brittle fracture in high-strength bolts shortly after installation.
Which of the following is the best method to prevent self-loosening in fastener joints subjected to transverse vibration?
Answer: Increasing clamp load above the vibration loosening threshold
Junker testing shows that maintaining sufficient clamp load prevents the micro-slip between mating threads that causes self-loosening under transverse vibration.
Galling between a stainless steel bolt and a stainless steel nut is most effectively prevented by:
Answer: Applying anti-seize compound
Anti-seize compounds create a barrier between similar metallic surfaces, preventing the adhesive welding (galling) that occurs with austenitic stainless steel.
A fastener exhibits significant necking and cup-and-cone fracture morphology. This indicates failure by:
Answer: Ductile overload
Cup-and-cone fracture with significant necking is characteristic of ductile overload failure, indicating the fastener was subjected to a single static load exceeding its tensile strength.