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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: Henry Davis (henry.davis@honeywell.com )
Organization:Honeywell
Date posted: Wed Nov 29 12:21:55 US/Eastern 2000
Subject: HALT/HAST testing
Message:
We are attempting to develop and correlate a service life specification requirement with a HALT/HAST test on an Line Replaceable Unit. We will need to develop the HALT/HAST test. Alternatively, we have a TAAF definition including duration, temp cycling and vibration levels and want to translate this to a service life number. Would appreciate any data or information on methodology (examples would be useful)for doing either of the above. Thanks for any assistance.


Reply:

Subject: HALT/HASS Testing
Reply Posted by: Bruce Dudley (bdudley@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Thu Nov 30 14:49:32 US/Eastern 2000
Message:
The term HALT was coined by Gregg K. Hobbs and is a development test concept. The testing is typically used to identify design or component weaknesses anfd manufacturing process problems by increasing the stress until failure occurs. The results of the stress testing are used to increase the margin of strngth of the design rather than to predict quantitative life or reliability of the product. Correlation of this type of test data to actual use is very difficult as some of the failures modes exposed may not occur in the normal operating or non-operating envelop. Accelerated tests that allow one to extrapolate test data usually conform to one of the fixed standards such as constant temperature tests, repeative mechanical fatigue tests, high voltage tests, humidity tests or a combimation test. All of these tests are performed within the maximum limits , so the failure modes should be representative of the normal envelop. Additional information on accelerated testing can be seen on the RAC home page which calls out data sheets for the START (selected topics in assurance related technologies)reports. Other information includes: Wayne Nelson's book "Accelerated Testing " and C.M. Harris's book "Shock and Vibration".


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