Sonic loading is a high frequency

broadband random process. Basic cycle counting methods

which are prevalently used in time domain

are difficult to be applied. According to present cumulative fatigue damage theories

the key to structure fatigue life analysis under sonic loading is to obtain the probability density function (pdf) of rainflow ranges directly form frequency domain. This paper analyzes some frequency domain approaches

which can obtain the pdf of rain-flow ranges from fatigue stress power spectral density (PSD) data. Some suggestions of promising method for aeroengine structural sonic fatigue analysis are given.