Failure Analysis & Testing Flashcards
7 cards from real CRE 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 & Testing flashcards as text
Which statistical test is most appropriate for determining if two groups of failure times come from the same distribution?
Answer: Log-rank (Mantel-Cox) test
The log-rank test is specifically designed to compare survival distributions from two or more groups, making it ideal for comparing failure time datasets.
Creep failure in metals is primarily a concern when operating temperatures exceed approximately:
Answer: 50% of the melting point in Kelvin
Creep becomes significant when operating temperature exceeds roughly 0.4–0.5 of the homologous temperature (melting point in Kelvin), where thermally activated diffusion mechanisms activate.
In FMEA, a detection rating of 1 means:
Answer: The failure mode is almost certain to be detected before reaching the customer
In standard FMEA scales, a detection rating of 1 represents the highest detection capability — the failure mode will almost certainly be caught before delivery.
What does the term 'design of experiments' (DOE) contribute to accelerated life testing?
Answer: It enables efficient testing of multiple stress factors and their interactions simultaneously
DOE allows testers to efficiently study the main effects and interactions of multiple stress factors using fewer test units than a full factorial experiment.
A component experiencing fretting damage will most likely show evidence of:
Answer: Red or black oxide debris at the contact interface
Fretting produces fine metallic debris that oxidizes, creating characteristic red (iron oxide) or black debris at the contact interface between oscillating surfaces.
The purpose of a 'fault tree analysis' (FTA) is best described as:
Answer: A top-down deductive analysis linking a top-level event to its causes
FTA is a top-down, deductive technique that uses Boolean logic gates to model the combinations of events or failures that can lead to a defined top-level undesired event.
When using the time-temperature superposition principle in polymer reliability testing, shifting data along the time axis at different temperatures allows engineers to:
Answer: Predict long-term mechanical behavior from short-term accelerated test data
Time-temperature superposition shifts creep or relaxation curves measured at multiple temperatures to construct a master curve that predicts behavior over much longer time scales.