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Reliability Requirement Understanding

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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

    Your customer is ignorant.

    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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