The Development of Fatigue/Crack Growth Analysis Loading Spectra,

Abstract : A realistic loading spectrum is a necessity in order to predict the fatigue or crack growth life of a component. Realistic loading spectra encompass many disciplines, including loads, stress, fatigue and crack growth analysis, and the realism of the spectrum will be dependent on the accuracy of the input data and the degree of complexity that the analyst is able or willing to undertake. External factors such as time and money considerations, available data, degree of accuracy required, etc., also affect the process of spectrum development and these factors often force the use of simpler, less time consuming, less expensive techniques than those desired to produce adequately realistic results. Steps in developing a loading spectrum which are covered in this report include: mission profile definition; loading environment; loading conditions; structural loads analysis; stress analysis; and stress sequencing. The simpler techniques available are discussed whenever appropriate. A detailed example of a spectrum development on a fighter/strike aircraft is included.