Weibul Analysis - HELP
Weibul Analysis - HELP
(OP)
I need to run a Weibul Analysis for my testing and am looking for some information about it. I have never used it before for testing and not exactly sure what it is. I have to meet a R95C90 level form my tests. I've looked at some brief Weibul examples on the web but am still a little confused. I found a program that you can input your Reliabilty and Confidence level and it determines how many sample parts must be tested to one life. Then it says you can reduce the sample size by using the Weibul Slope. Where do I determine what the Weibul Slope is?
If anyone can give me some information about doing a Weibul Analysis I would greatly appreciate it.
Thanks,
Chad
Product Engineer
If anyone can give me some information about doing a Weibul Analysis I would greatly appreciate it.
Thanks,
Chad
Product Engineer





RE: Weibul Analysis - HELP
Basically and quickly Weibull analysis consits of plotting failure rate vs. time on log-log paper. You will wind up with a straight, a concave or convex curve, or a "S" shaped curve. If straight you are OK. if curved you need to make adjustments to the curve to make it straight. ( This is where the software helps). If "S" shaped the curve is invalid.
Regards
Dave
RE: Weibul Analysis - HELP
As far as software is concerned I can wholeheartedly recommend WeibullSmith from Fulton Findings (http://www.weibullnews.com/contents.htm and ht
This package uses just your data to produce results, no guessing at parameters. It's good.
I'm no statistics expert, but here goes with my understanding. I'll apologise in advance for teaching sucking eggs.
The first thing to appreciate is the so-called 'bathtub curve'. Check here: http
If you want to plot straight lines, you need special Weibull graph paper, either '2-cycle' or '3-cycle' with the vertical axis showing cumulative density function. http://www.weibull.com/hotwire/issue8/rb8_7.gif
I used to find that, if I set out to test 8 samples to failure, then using the Fulton software, I often had enough data after 5 failures to get a good fit and respectable results.
This assumes that the design under study does not suffer from multiple failure mechanisms and that any manufacturing processes are stable.
Bill