Mechanical Reliability

Abstract

Mechanical reliability is a very old subject; for as long as humans have built things, they have wanted to make them as reliable as possible. Mechanical systems were overdesigned by using larger safety factors in the past to avoid failures. Mechanical reliability takes into consideration material engineering, durability of the components, tribology aspects of products, operating conditions, environment, and mechanics. Further, understanding of statistics and probability is primary to understanding and creating a reliable mechanical system.

It is very difficult to predict the reliability of mechanical components designed for a specific system. The variables affecting the reliability include manufacturing variation, material variation, variation in operational loading, duty cycle, environment, etc. There are some models developed using physics-of-failure techniques in order to predict the reliability of these components. Though these methods are useful to know the sensitivity of the design parameters on the overall reliability of the product, it is important to validate the product in the expected loading and environmental conditions.

Part of generating the valuable historical data to predict future reliability of mechanical components is classifying their failure. For example, the best data on when the maintenance for a bearing in grinding equipment should be replaced would include when the bearings in a similar type of grinding equipment needed replacing previously. Obviously, for new systems, this is not possible. Reliability data from the existing systems can be considered for the new designs if the new design is quite similar to the current systems. For completely new designs, however, alternative means of estimating reliability must be employed.

It is obvious that mechanical parts, like most other items, do not survive indefinitely without maintenance. A large portion of mechanical reliability is determining when maintenance should be done in order to prevent a failure.