# Reliability Requirement Understanding

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Viewing 9 posts - 1 through 9 (of 9 total)
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• #249718

Yaron
Participant

I have got the following requirement that I’m a little bit struggling to understand how was it calculated.

“A limiting curve of failure behavior for the new component will be defined: with Weibull distribution and shape parameter Beta=1.00. The curve is based on field analysis of previous component. The failure probability at 17.500 km is equal 0.34%. The second node is located by 100.000 km mileage and a failure probability of 1.94%.” in addition to this a confidence level of 90% was defined.

Is there a missing information here? I thought it was calculated using the Weibull CDF but the numbers I receive are different. As alpha I have used 100,000km.

Appreciate if somebody can clarify what I am missing.

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#249725

Fausto Galetto
Participant

If you provide the data I will see what I can do.

I do not understand what do you mean with “””second node”””

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#249735

Yaron
Participant

This is the problem that this all information I have. My assumption is that the failure has weibull distribution. The customer provided only two points of his interest. One is at 17,500km another at 100,000 km. I  assumed that the “failure probability” indicates commulative failure up to the above mentioned milage and tried to model the curve but the failure rates I have recieved do not alighn with the one were provided by the customer.

so I’m a little stuck.

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#249743

Fausto Galetto
Participant

The information provided is contradictory: beta=1 and the two points.

From the reliability curve, any educated “manager” derives beta=0.743

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#249771

Yaron
Participant

Thanks. I also thought something wrong with the requirement but was not sure.

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#249773

Yaron
Participant

By the way, how did you get to beta=0.743? Thanks.

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#249781

Fausto Galetto
Participant

Fitting the Weibull to pass through the two points!!!

You must study a bit of THEORY

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#249823

Yaron
Participant

Appriciate for your kidness. what SW are you using to fit the destribution?

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#249830

Fausto Galetto
Participant

NO SW!!!

Only a bit of Mathematics…

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