Part subjected to more than one failure mode
Part subjected to more than one failure mode
(OP)
Hi gents,
When a part is subjected to more than a single failure mode, each one described by a Weibull distribution, how do you determine the combined failure frequency? I get it easily by using Monte-Carlo simulation but it becomes rather different when it comes to analytics. I have made a few attempts following different reasoning but haven´t succeeded so far – results just don´t match! For instance:
Failure mode A: beta = 2.5; eta = 3,300 hours
Failure mode B: beta = 3.2; eta = 3,750 hours
MC simulation yields 0.00041 failures/hour.
Any help will be much appreciated. Thanks.
When a part is subjected to more than a single failure mode, each one described by a Weibull distribution, how do you determine the combined failure frequency? I get it easily by using Monte-Carlo simulation but it becomes rather different when it comes to analytics. I have made a few attempts following different reasoning but haven´t succeeded so far – results just don´t match! For instance:
Failure mode A: beta = 2.5; eta = 3,300 hours
Failure mode B: beta = 3.2; eta = 3,750 hours
MC simulation yields 0.00041 failures/hour.
Any help will be much appreciated. Thanks.
RE: Part subjected to more than one failure mode
RE: Part subjected to more than one failure mode
Allow me to call your attention for the fact that the case I described involves different failure modes and not different parts each one with a predominant failure mode (in which case, the problem would be very simple to solve). Only in this later case, it would be necessary to know whether the failure modes were independent or not and, if affirmative, the crossed probabilities of one part causing the failure of the other would be necessary too.
RE: Part subjected to more than one failure mode
RE: Part subjected to more than one failure mode
When such a situation occurs, the computation of the reorder point for parts kept in stock becomes difficult. I normally solve this type of problem by recurring to Monte Carlo simulation in EXCEL, but it takes too long and cannot be automated. Things get still worse when a preventive routine is in place and the part is to be replaced every X hours of running time.
Thanks,
RE: Part subjected to more than one failure mode
Typical weibull analysis for mixed failure mode has no significance, beta do not tell what is happen. But if you use the Bi-Weibull model you can analyze them and get the combined failure frequency. RELCODE soft has the chance to analyze this problem with the Bi-Weibull distribution model. If you cant get acces to RELCOE you can send me your Time To Failure of each one and i will simulate for you.An alternative that is more conservative is to get the average of lambda. Lambda(average)=-ln(R(t))/t
Regards
Fernando
RE: Part subjected to more than one failure mode
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