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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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Posted by: Keith Chinchar ( )
Date posted: Wed Oct 25 14:09:32 US/Eastern 2000
Subject: Endurance versus HALT
I'm performing HALT tests to demonstrate MTBF for electronic assemblies (power supplies in particular). I understand the application of the various acceleration models (Arrhenius, Peck, Kemeny, Lawson, etc.) for adding the stresses of temperature, humidity and voltage (et. all)to obtain an acceleration factor. However, I've run into a situation that adds the stress of cycling a unit on and off (demonstrating a duty cycle) during the duration of the test. I realize that this will cause a thermal cycling effect on the multitude of failure mechanisms within my device. I'm planning to run my test at an elevated temperature and apply the Arrhenius model to obtain an acceleration factor. How do I estimate an acceleration factor that takes into account the duty cycle (it would need to consider the duty cycle and the total number of cycles over the life expectancy of the product)? Will the Coffin-Manson relationship / inverse power law apply here? Any help is appreciated. Thanks in advance


Subject: Endurance versus HALT
Reply Posted by: Ken Tonnesen ( )
Organization: Reliability Analysis Center
Date Posted: Wed Nov 1 13:13:57 US/Eastern 2000
Subject: Endurance versus HALT Cycling the unit on and off will create some thermal cycling stress. This is separate from the elevated temperature stress and has its own acceleration factor. This acceleration factor is determined empirically or it can be based on historical test experience. The RAC's PRISM software can aid in estimating an acceleration factor for a duty cycle in this type of testing. This program has the capability of projecting reliability values for on-off cycling.

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