Forum: Reliability & Maintainability Questions and Answers
Posted by: ravi
Date posted: Sat Sep 11 2:18:09 US/Eastern 2004
Hi, How can we use house events in FTA to model different operational phases of system? Some literature links or a small example will be useful. Thank You.
Posted by: C K (firstname.lastname@example.org )
Organization:DSO National Laboratories
Date posted: Wed Sep 8 22:57:05 US/Eastern 2004
Subject: ESS vs EWT
Recently, I came across some statements in MIL-STD-810F, Method 514.5 (pg 514.5-1, para 1.2e and Annex B, para 2.1.8) on ESS. In para 1.2e, it was written that "Where units do not necessarily receive the same exposures, such as multiple passes throuth ESS, apply the maximum allowable exposures to the units used for environmental test as pre-conditioning for the environment tests."
In Annex B, para 2.1.8, it says EWT can be used to substitute ESS when the material is to be subjected to worthiness test and then used in the field. My questions are: 1) Can EWT really be used to substitute ESS for the scenerio mentioned in Annex B? 2) What if my unit is only subject to 1 grms vibration (human transportation) in field, is EWT of 1 grms, 10mins/axis for 3 axes sufficient to replace ESS? 3) If I conduct ESS on the said unit using 6 grms, 10 mins/axis (critical axis only), will it kill the unit? Kindly advise. Thanks.
Posted by: D. Young (email@example.com )
Date posted: Tue Aug 31 16:10:16 US/Eastern 2004
Subject: Reliablity Prediction Factor
Simple question, if I'm using the NPRD-95 book to do a reliablity prediction analysis and there's an item which only has a value for a GM environment. Is there a conversion factor that I can use to reflect an AIF environment? PLEASE HELP.
Posted by: Bob Valerius (firstname.lastname@example.org )
Organization:Northrop-Grumman Oceanic Systems
Date posted: Tue Aug 17 14:32:39 US/Eastern 2004
Subject: Failure rate of a copper trace on a circuit board
Does anyone have a failure rate for simply the copper trace on a circuit board. I was thinking of using sections 16 of MIL-HDBK-217F but I don't think they apply. Thanks! Bob Valerius
Posted by: Per Jonsson (email@example.com )
Date posted: Mon Aug 16 8:31:11 US/Eastern 2004
Subject: Long term storage of electronics
I have a question about electronics in general and circuit boards in particular. Is there research done about how long it is possible to store electronic devices? Does anything happen if you store a cicuit for more than 20 years or is there a good chanse that everything works allright even after so many years. Is there any actions to take during storage to decrease the risk of failure?
Thanks for any help on the subject! /Per