Cycle distribution and fatigue damage under broad-band random loading

Fatigue damage under broad-band loading is analysed by summarizing and reviewing available analytical solutions. Relationships between fatigue damage assessment and counting methods are investigated by establishing when, in frequency domain analysis, analytical solutions of expected damage are connected with a counting procedure assumption and how this is related to the rainflow counting procedure. A new approach is also proposed for rainflow damage evaluation. This approach gives accurate approximations of fatigue damage under both broad- and narrow-band Gaussian loading; it is based on the theoretical investigation of possible combinations of peaks and valleys in Gaussian loading and on numerical fitting on several simulated broad-band loads.