Standardised Fatigue loading Sequences for Helicopter Rotors (Helix and Felix) Part 1. Background and Fatigue Evaluation

摘要

A standard loading sequence is a variable amplitude repeated sequence of peak and trough loads to be applied in fatigue and crack propagation tests. Each standard represents loading on a particular class of engineering structure. Two such existing standards are FALSTAFF (Fighter Aircraft Loading STAndard For Fatigue evaluation) and TWIST (Transport WIng STandard). which represent loading on fighter and transport aircraft wings respectively. Their developement has arisen form the fact that, often, life prediction methods are not accurate enough to predict fatigue lives or crack rates adequately under service (variable amplitude) loading conditions. Therefore when making a fatigue assessment of, for instance, a new detail, fastening system or method of life improvement, variable amplitude loading has to be used. Often such tests are not tied specifically to any particular project, but are for more general application. In this case a standard sequence, provided a relevant one exists, is often the best choice for the test loading. The advantage of using standard sequences in this situation is that any resulting data can be compared directly with any other obtained using the same standard as well as being capable of being used as design data. This report describes the derivation and fatigue assessment of two loading standards for the fatigue evaluation of helicopter rotor materials and components. Additional keywords include: Statistical tests.