Fatigue limit – Material property as an opened or closed system? Practical view on the aircraft components failures in GCF area

In the presented paper the macroscopically seen phenomenon of the fatigue crack originating inside of specimens in area of very-high-cycle fatigue (VHCF) for lifetime to failure more than 109 cycles is explained on the basis of synergetic approaches when the knowledge about bifurcation’s points used to show self-organized change in material sensitiveness to cyclic loads in different media areas where exceeds maximum stress-state. The discussed bifurcation diagram was constructed, using knowledge about scale levels for plastic deformation processes. This synergetic view on the cause of the fatigue crack origin displacement from the materials surface in area of high cycle fatigue (HCF) to the inside of specimens is illustrated by fatigue tests results for hardened materials of Ti- and Al-based alloys in areas of low cycle fatigue (LCF) and HCF.The cracks distribution in time for in-service fatigued aircraft components has three pikes of their maximum failure intensity. This situation is general for all components operated in areas of LCF–HCF–VHCF. Aircraft components failures features in area of VHCF are discussed for blades of Ti-, Al-, and Ni-based alloys, gears of helicopters reducers, and shafts of aircraft engines.