FRACTOGRAPHIC DETERMINATION OF FATIGUE CRACK GROWTH RATES IN AIRCRAFT COMPONENTS.

The application of electron fractography to the failure analysis of aircraft components is considered to be rewarding because it frequently permits the precise identification of the causes of component failure. Quantitatively, considerable effort has been devoted to the development of techniques specifically directed to the evaluation of fatigue crack growth rate information, both from service fatigue failures, and from components fractured during full-scale aircraft laboratory fatigue tests. Recent use of computer-controlled random fatigue loading equipment has produced problems associated with the identification and correlation of the randomly spaced fatigue striations on the fracture surface, and the derivation of crack growth rate data from them. The fractographic methods developed for the solution of these problems are described.