AGMA 17FTM12 [ Active ]

The most important criteria for the design of a gearbox is a sufficient strength of all components. There are, however, different ways to define this demand. The two most common ones are either defining minimum required safety factors for a given lifetime or prescribing a minimum likelihood to achieve a certain lifetime, often expressed in the reliability of a component within a given lifetime. This paper discusses the different approaches and the relationship between the safety factors and the calculation of the reliabilities. It will concentrate on ISO and AGMA standards for gears, shafts and bearings and will only discuss endurance calculations, no static calculations.

After an introduction to the concept of reliability calculation based on the book of Bertsche [2], an example to show the difference between safety factor and reliability is given. Afterwards, the built-in reliability coefficients of ISO 281 and AGMA 2001-D04 are compared to the general approach in Bertsche.