Probability of multi failures
Probability of multi failures
(OP)
For the fatigue assessment of a welded component, an SN curve is given that is generally a line of best fit through data of stress (S) against the number of cycles to failure (N).
What is the probability of 2 or more welded components, subject to the same stress, failing at the same time or failing within a certain number of cycles of each other?
What is the probability of 2 or more welded components, subject to the same stress, failing at the same time or failing within a certain number of cycles of each other?
corus





RE: Probability of multi failures
We can fairly confidently say that p(n1=n2)=~0 if n1>1000
You could do a Weibull analysis.
http://www.weibull.com/
for a hideously complicated explanation. Also http://www.itl.nist.gov/div898/handbook/eda/section4/ed...
shows a worked example of how you do a weibull analysis in practice
Failing that, an ad hoc approach is to say that on average the mean life is .5(n1+n2), and on average 1/3 of the population will fail before n1, 1/3 between n1 and n2, and one third above n2. The proper analysis of this actually gives 29% below n1, and 29% above n2, and obviously 42% between them.
http://www.itl.nist.gov/div898/handbook/pmc/section3/pm...
describes how to estimate standard deviations from small sample sizes.
Cheers
Greg Locock