Transfer-function Approximations of the Rainflow Filter

Georg Lindgren and Jesper Rydén

Centre for Mathematical Sciences
Mathematical Statistics
Lund Institute of Technology,
Lund University,

ISSN 1403-9338
The rainflow filter is a non-linear filter which can be used to eliminate small-amplitude oscillations in a signal.
In this paper, two approaches for investigation of the filter by means of an approximating transfer function are presented. The estimates are obtained from rainflow filtered spectral simulations. One method is based on
clipped Gaussian processes, the other uses a spline interpolation in the filtered time series. Examples are given for processes with different types of spectral densities. A certain reduction of small-amplitude cycles is obtained by use of the transfer function, but the threshold effect, characteristic for the rainflow filter, is missed.
Key words:
waves, spectrum, rainflow cycle, filtering, fatigue