Dirlik Formula

Fatigue analysis has traditionally been performed in the time domain, where cycles in a random stress or strain time history are identified using the rainflow cycle counting process.

However, some structures are subject to random loading, which may be more convenient to describe in the frequency domain by a Power Spectral Density (PSD) function.

Much interest has been shown in fatigue damage analysis and possibly a rainflow range count, directly from PSD.

Dirlik has produced an empirical solution, which can be used to obtain the rainflow range probability density function from PSD data.

The formula is commonly used offshore and in automotive industries.