Abstract / scope
ISO 281:2007 introduced a life modification factor, aISO, based on a systems approach to life calculation, in addition to the life modification factor, a1.These factors are applied in the modified rating life equation, Lnm = a1aISOL10. The modification factor for reliability, a1, for a range of reliability values, is given in ISO 281:2007 as well as the method for evaluating the modification factor for systems approach, aISO. L10 is the basic rating life.
ISO/TR 1281-2:2008 gives supplementary background information regarding the derivation of a1 and aISO.