Forum: Reliability & Maintainability Questions and Answers
Posted by: Soon-wook, Jung (firstname.lastname@example.org )
Date posted: Mon Jan 12 3:18:16 US/Eastern 2004
Subject: Reliability of Motor in Missile, Rocket
Hi! I'm a reliability engineer, working in HANWHA Corp.
Did you have been produced datum of prediction reliability of Missile, Rocket system? I should want to get reliability datum of parts of Missile, Rocket. Please, could you help me?
Posted by: laewon kim (email@example.com )
Date posted: Wed Jan 7 20:08:56 US/Eastern 2004
Subject: About RCM standard
Hi I,m laewon kim
Posted by: Andrew Rowland (firstname.lastname@example.org )
Date posted: Mon Jan 5 14:49:48 US/Eastern 2004
Subject: System Reliability Analysis
I have a system that was originally placed in service in late 70's. Computerized maintenance records are not available until June 1991. Also, the records are not typically detailed enough to bin by failure mode. Essentially, the statistic I have available is "time of repair request".
I have considered cumulative time to repair request with t0 = June 1, 1991. Using truncated portions of example data from MIL-HDBK-189, I find this approach unacceptable. I also find that goodness of fit tests of my actual data typically fail with this approach. The other approach I have considered is time between repair requests, since these times would be independent of actual system age. This would, then, allow me to determine the recurrence rate. I could use this recurrence rate in subsequent modeling with the understanding that times must be accurately specified. Is there an optimal methodology for handling truncated system repair data such as mine? Thanks.
Posted by: Tony Nguyen (email@example.com )
Date posted: Tue Dec 16 11:04:42 US/Eastern 2003
Is there a formula to calculate the MTBCF from typical MTBF/FITs data. Please help.
Posted by: Destin LeBlanc (Destin.LeBlanc@craneaerospace.com )
Date posted: Fri Dec 12 20:10:30 US/Eastern 2003
Subject: Resistor short circuit failure modes/FMD-97
In RAC's Failure Mode/Mechanism Distributions 1997 (FMD-97), the failure mode "Shorted" is given for Resistors (I'm specifically looking at "Resistor, Fixed, Wirewound" here). My EEs are telling me this is completely impossible, but every FMEA I've ever seen has considered "Resistor Shorted" as a possible failure mode.
Unfortunately, many many web searches on the possible combinations of keywords here have yielded almost no results; I've seen as many people saying shorted resistors are a failure to consider as saying that it is impossible (and I can count them each on one hand). So I'm hoping somebody can shed some more light on this situation. Are the failures listed in FMD-97 only manufacturing defects (ie, not a result of an operational situation)? Is it possible to say for sure that, if you drive too much current through a resistor, it *won't* fail shorted? [I would assume knowledge of the physical construction of resistors would tell us that.] Thanks!