Fatigue failure of aircraft components

Despite the fact that most engineers and designers are aware of fatigue, and that a vast amount of experimental data has been generated on the fatigue properties of various metallic and non-metallic materials, fatigue failures of engineering components are still common. Statistics show that majority of service failures in aircraft components occur by fatigue and it amounts to about 60% of the total failures. A number of factors influence the fatigue life of a component in service, viz., (i) complex stress cycles, (ii) engineering design, (iii) manufacturing and inspection, (iv) service conditions and environment and (v) material of construction. Analysis shows that premature fatigue crack initiation in the components can be attributed to defects of various types introduced mostly inadvertently in various stages of component design, manufacture, maintenance, inspection, operation etc. A large number of such failures have been investigated in the authors’ laboratory over the past many years and a few of them are highlighted in this paper.