Design for Reliability and Safety Flashcards
What is single point failure
a single failure that leads to catastrophic failure
What is common mode failure
single effect that causes several sub-systems to fail
What is cascade failure
one failure that leads to another
What is a fault intolerant system
single failure causes system to fail (chain)
What is a fail safe
fail in a non-catastrophic way
What is a safe life
period of safe operation
Failure rate (lambda)
number of fails per time period
Mean time between failures (MTBF)
1/lambda
What 3 trends to failure distributions follow
exponential, normal, Weibull
Equation for component reliability
R(t) = exp(-lambda*t)
What are non-redundant components
a product which consists of a number of components that must all work for the product to function
What is ‘One-in-two’ element redundancy
Fault tolerant system as system can still function if one of two components fail (computers on an aircraft)
What effect does maximising m and n for a given m/n ratio have
The more components there are the less chance it will fail (3/6 is better than 1/2)
Name 3 ways a fail safe can fail a system safely
Overheating causing a fuse to trip
Ductile failure saving loss of structural support
Twin circuits in tandem
What does FMECA stand for
Failure mode effects and criticality analysis
