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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: Anil
Date posted: Wed Jul 9 2:07:26 US/Eastern 2003
Subject: Reliability testing vs Durability testing
Message:
Could you please help me out in this? What is the difference between Reliability testing and Durability testing? Can you please give one automotive component example for both type of testings?


Reply:

Subject: Testing
Reply Posted by: BWD (bdudley@alionscience.com )
Organization: RAC
Date Posted: Wed Jul 9 11:44:40 US/Eastern 2003
Message:
Durability is defined as the length of failure free or maintenance free operation period. The basic assumption is that all failures are caused by applied electrical, mechanical or thermal stress and there are no failures before the end of the failure free period [useful life] is reached. This process is predicated on being able to quantify the loads or stresses that are applied to the electronic or mechanical components and relating these conditions to cycles to failure for repeating and varying load conditions. Therefore, a durability test is a test to failure to determine the length of the failure free period. Units are stressed as expected in the operating environment or are accelerated by increasing the stress levels. Testing is stopped at failure of all the units. A reliability test is a time based test related to the failure of chance defects in the product. A number of unit are tested for a period of time and the data are accumulated [time and failures]. The mean time between failure is determined by the number of accrued hours and failures. The test is not stopped at failure but continues to a predetermine time. An example is the fuel pump used in automobiles. The durability failure free time is expected to be 100,000 miles or 5,000 operating hours. The reliability of the pump is 40.0 failures per million hours [NPRD data] or an MTBF [mean time between failure] of 25,000 hours.


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