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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum ( )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Original Message:

Posted by: Adon Looi ( )
Organization:Singapore Engineering Software
Date posted: Wed Jan 26 20:23:41 US/Eastern 2000
Subject: Reliability Prediction on different environment
Hi, I need some advise on the reliability prediction. If I uses the MTBF predicted for Ground Fixed environment in Ground Mobile environment, that means that I have to degrade the MTBF by a factor of 0.2 as refered in the Reliability Toolkit for Commerical Practices. However, as the equipment will be ruggedised and isolator and shock pad are included to minimise the vibration and shock level, does that means that the factor of 0.2 does not stand anymore and I can asssume that the MTBF of GF is more or less equivalent to GM.


Subject: Toolkit Conversion Factors
Reply Posted by: Bruce Dudley ( )
Organization: Reliability Analysis Center
Date Posted: Thu Jan 27 13:23:50 US/Eastern 2000
Received your question and as you are the analyst you can make any assumptions that are necessary to portray the item in its best position to sell to the user. Your problem is will the user or operator believe you. The conversion factors in the Reliability Toolkit; Commercial Practices Edition are presented to give one the opportunity to make a "quick" assessment of reliability figures of merit from the designed "to" stress level to a different stress condition. It is not intended to evaluate "design fixes" such as adding isolators. For this condition, the unit should be reevaluated using the actual stress conditions for the MOBILE application with the new design improvements to find the real reliability of the item for the "MOBILE" conditions. Your assumption that GF~GM with the addition of isolators is not rational from my prospective as temperature cycling and range and electrical stresses (voltage / current conditioning) are significant parameters that should be impacted by higher stresses and need to be considered in the evaluation process.

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