SRC Forum - Message Replies
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
Posted by: Jim Jones
Date posted: Tue Feb 11 12:53:30 US/Eastern 2003
Subject: Durability definition
I am in need of a definition of both electrical durability and mechanical durability. In what ways is the durability of an item tied to material used in the design? How does durability differ from normal wear-out?
Reply Posted by: B.W.D.
Date Posted: Tue Feb 18 12:55:57 US/Eastern 2003
Durability is defined as the length of failure free or maintenance free operation period. The basic assumption is that all failure are caused by applied mechanical / thermal stresses 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.
Wear-out is the process that results in an increase of failure rate or probability of failure as the number of life units increase. So, the difference is the durability function is the initial part of the life operation up to the point where failure starts. Wear-out is the next step after durability.
Reliability descriptions and definitions are contained in the Reliability Toolkit; Commercial Practices Edition and in MIL-HDBK-338 Electronic Reliability Design Handbook.