Forum: Reliability & Maintainability Questions and Answers

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Posted by: speo (speo@jat.co.kr )
Organization:JasonTech.Ltd
Date posted: Thu Jul 6 1:55:42 US/Eastern 2000
Subject: FMD-97
Message:
The number of component number from FMD-97(91), RAC is more much than MIL-STD-338B? or is they same together?
How many kinds are components of FMD-97 ? And I want to know other failmode databases and where I get it. Thank you!

Replies:
FMD-97
Jack Farrell Fri Jul 7 15:44:01 US/Eastern 2000

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Posted by: Peet (pvdmerwe@grintek.com )
Organization:Grintek Electronic Systems
Date posted: Tue Jul 4 8:50:45 US/Eastern 2000
Subject: Reliability Prediction - Compensation for Shock Mountings
Message:
When performing a reliability prediction for a product being used in, for example, an airborne rotary wing environment (ARW). All available software packages that I know of does make provision for selection of the global environment, while in some cases you can select different environments for different products within a system. How would one distingiush between a product mounted directly into the cocpit of a chopper and one that is mounted onto a well designed shock obsorber that dimenishes the effect of vibrations and bumbs? Obviously, the product on the shock mount lives in a more friendly environment, but which of the available environments do you choose?
Best Regards Peet

Replies:
Product Use Environments
Jack Farrell Thu Jul 6 16:12:21 US/Eastern 2000

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Posted by: James
Date posted: Mon Jun 26 17:50:57 US/Eastern 2000
Subject: Pi Factors in 217
Message:
In 217, I noticed that there are two factors (power rating factor and voltage stress factor) in the equation of Bipolar (transistors, low freq.) , but not in Si FET (transistor, low freq.). Why? I think there are still some power and voltage effects on the failure rate of FET. Could I use the tables in Biploar to modify the equation of FET?
Thanks in advance! James

Replies:
MIL-HDBK-217 Low Frequecy Transistor Model
Jack Farrell Fri Jun 30 10:46:06 US/Eastern 2000

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Posted by: Bill Crabb (bill.crabb@verhaert.com )
Organization:Verhaert Design & Development N.V.
Date posted: Fri Jun 23 4:38:11 US/Eastern 2000
Subject: Derating
Message:
Derating rules for MIL-SPEC components are given in MIL-STD-975, the GSFC PPL-21, JPL-D-8545, NAVSEA TE000-AB-GTP-010, ESA PSS-01-301, MIL-HDBK-1547, and in the RAC Reliability Toolkit. However I want derating rules for commercial components in the commercial environment, but so far I can find nothing. Are there any rules or guidelines out there?
(Look forward to the new RAC publication on this subject - next month?). Bill Crabb, Componbent Engineer/Parts Specialist.

Replies:
Derating of Commercial Parts
Bruce Dudley Mon Jun 26 14:56:08 US/Eastern 2000

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Posted by: swami (swami@futron.com )
Organization:Futron
Date posted: Thu Jun 15 16:20:22 US/Eastern 2000
Subject: bellcore/mil217 values
Message:
We are trying to use data from Bellcore and Mil-Std-217 for getting failure rate data of various components. We are also interested in constructing uncertainty distributions on these failure rates.
Is the value of failure rate from Mil-217 to be considered the mean failure rate of the component ? Is the value from Bellcore the mean failure rate or the 90% upper bound on the failure rate ?

Replies:
Mil-Hdbk-217, Bellcore Failure Rates
Jack Farrell Wed Jun 21 13:59:11 US/Eastern 2000

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