Forum: Reliability & Maintainability Questions and Answers

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Posted by: Cloarec (jean-marie.cloarec@ligeron.com )
Organization:Liigeron SA
Date posted: Mon Mar 10 9:15:08 US/Eastern 2003
Subject: MTBF and TBO
Message:
I need some explanation. I have a system whose TBO is 20000 hours. One guys find that the sytem MTBF = 18000h. So he would like to have a MTBF greater than TBO (he says that he don't want a failure at 18000 that need repair because it missed 2000hours to go to the TBO). I tried to explain him that there is no relation between MTBF and TBO. Have you some practical answer to explain this ?
Thanks

Replies:
TBO and MTBF
bwd Tue Mar 11 9:43:47 US/Eastern 2003

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Posted by: Hari (ch_hari_prasad@indiatimes.com )
Date posted: Sat Mar 8 0:24:41 US/Eastern 2003
Subject: Physical significance of Weibull Shape and scale paramenters
Message:
Someone can you help me please......
When statistically speaking shape decides the shape of the distribution(Whether it is normal,exponential,skewed distribution,etc....),Scale parameter decides the 63%of population fail with in that time.... When you convert this statical problem to physical problem(Practicle problem),On what properties this parameters depends........So in brief... What is the physical significance of Weibull shape and scale parameter?

Replies:
Weibull Parameters
Jorge Romeu Tue Mar 11 10:03:31 US/Eastern 2003

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Posted by: Shanta
Date posted: Thu Mar 6 15:58:08 US/Eastern 2003
Subject: PRISM
Message:
I am evaluating PRISM software. Where can I get a standard that has all the equations, pi factors and base failure rates? For eg. if I use MIL-HDBK-217FN2, I can look up the equations, pi factors, base failure rates etc in the standard which is available free of charge. If I use Telcordia, I can buy the standard from them. What about PRISM? Can I buy it from RAC or is it available free of charge on some website? Will I get a copy if I buy the software from RAC?

Replies:
PRISM Prediction Methodology
David Dylis Thu Mar 6 16:09:36 US/Eastern 2003

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Posted by: Sathees kumar Ramamoorthy (satheeskr@ctd.hcltech.com )
Organization:HCL Technologies
Date posted: Tue Mar 4 13:32:41 US/Eastern 2003
Subject: Reg - MIL HDBK 217F
Message:
Dear all,
MIL HDK 217F address for Memory chips upto 1M Bits size for calculation of Die Complexity Failure Rate(C1). we are using chips that are of 4 M Bits in size. Could we extrapolate the vaue from 1 M Bits or take the value for 1 M Bits.

Replies:
MIL-HDBK-217 Memories
BWD Tue Mar 4 15:51:36 US/Eastern 2003

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Posted by: chandu (chandra_hari@rediffmail.com )
Organization:Nagarjuna univeristy
Date posted: Tue Mar 4 6:33:32 US/Eastern 2003
Subject: PREDICITON OF PARAMETER
Message:
I have some laboratory data (accelerated test)for Grade 1 item and Grade 2 item, i have estimated parameters of weibull distribution. For the Grade 1 item i have field data and i have estimated the parameters of weibull distribution.
Here i have a problem in correlating the field data with laboratory data for grade 1 item. How can i correlate this Grade 1 data? By using this same same logic How can one predict the field data parameters for Grade 2 ? Please help me in this case....

Replies: (list all replies)
Test Extrapolation
bwd Tue Mar 4 16:15:06 US/Eastern 2003
Weibull accelerated and field reliability
Larry George Sun Mar 9 16:28:59 US/Eastern 2003
Correlating field life and lab data life
Hari Tue Apr 1 6:28:40 US/Eastern 2003

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