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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

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

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Original Message:

Posted by: Ian-C
Date posted: Wed Apr 11 6:55:36 US/Eastern 2001
Subject: Activation Energies
Message:
I have been supplied 3 temperature and humidity conditions (75C/90%RH; 85C/90%RH; 85C/65%RH) and 3 associated MTTF's. Is there a way that I can calculate the Activation Energy and humidity acceleration factor from this given information. If this is not possible, what other information would be required, other than the normal temperature and humidity operating conditions. (I would normally use the Peck model(Arrhenius-Lawson)for this) If it is not possible to calculate it under damp heat conditions can it be done for dry heat (Arrhenius only). Any help/advice will be greatly appreciated Thanks in advance


Reply:

Subject: Activation Energy
Reply Posted by: Edward Sherwin (esherwin@alionscience.com )
Organization: RAC
Date Posted: Mon Apr 16 14:26:32 US/Eastern 2001
Message:
The only sure way to determine the activation energy and humidity acceleration factors is through a structure design of experiments and plotting the result. Since RAC does not know the product, application, requirements, etc, we cannot recommend a calculation method that should be used to your specific task. We do recommend that you obtain a copy of a book on “Accelerated Testing” by Wayne Nelson. On pages 76,102 and 152, there are equations to calculate the activation energy and acceleration factors. The risk in using these equations is that the factor may not be proper for your situation


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