#11




Re: How to use test data of subsystems
Thank you for the link. I understand that you have previously discussed this method with someone from our Theoretical group. We will certainly consider it and get back to you if we have any questions.
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David 
#12




Re: How to use test data of subsystems
There is a continuation of this discussion at http://reliabilitydiscussion.com/showthread.php?t=2394.
Last edited by Oleg_I; November 13th, 2010 at 08:47 AM. 
#13




Re: How to use test data of subsystems
It seems a case of the paradox "whole  parts".
If we estimate a reliability of each component separately and use the typical (r1*r2*r3) we derive a low reliability of a system. But if we do not estimate a reliability of each component separately, how we do it for tests of the system we will get a higher estimation of reliability of a system. Mathematically it can be defined as: 1. Testing of the n systems with three components 1CL = (r1*r2*r3)^n => rs = (r1*r2*r3) = (1CL)^(1/n) 2. Testing of all components separately (the n tests of each component): 1CL = r1^n * r2^n * r3^n => rs = (r1*r2*r3) = (1CL)^(1/n)  the expression remains the same 3. Testing of all components separately (the n1 tests of 1st component, n2 tests of 2nd component, n3 tests of 3rd component, n1>n3, n2>n3): 1CL = r1^n1 * r2^n2 * r3^n3 => rs = (r1*r2*r3) = ((1CL)/r1^(n1n3)/r2^(n2n3))^(1/n3)  rs depend on r1, r2 here. Find rs>min (the worst case) therefore r1=1 r2=1 rs = r3 = (1CL)^(1/n3) For example: n1=50, n2=60, n3=27, CL=0.9 The method <http://www.reliasoft.com/pubs/2010_R...ot_systems.pdf> gives us rs=0.874 (see attachment) This method gives us rs=(10.9)^(1/27)=0.918 What is correctly? Last edited by Oleg_I; November 19th, 2010 at 06:37 AM. 
#14




Re: How to use test data of subsystems
There is a continuation of this topic http://nomtbf.com/2016/04/lifetimeevaluationvsmeasurementpart2/#more1888

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