The Rainflow DataMode™ stores multiple channels of rainflow cycle histograms in the output data file. The CX23-R/eDAQXR acquires peaks and valleys from triggered or un-triggered time history data streams using the user-specified hysteresis value and the peak valley processing algorithm. The resulting peak valley stream runs through the rainflow cycle counting algorithm to yield the set of closed cycles. The closed cycles are histogrammed using the user-defined options for the type and size of histogram.
NOTE
When a large number of channels are selected for a DataMode, the GUI responsiveness can become sluggish. Typically with 500 channels or less, this is not overly intrusive to usability. However, if more than 500 channels are required for any given DataMode, it is recommended that users consider splitting the channels across multiple DataModes when possible; otherwise, users will need to be patient in regard to the GUI response when assigning or editing any of the DataMode parameters.
NOTE
The cumulative size of all histogram matrices across all Rainflow, Peak Valley Matrix and Time at Level DataModes is limited to 650 MB.
DataModes options
After initializing, the peak valley processing algorithm alternates searching for peaks and valleys based on the user-defined hysteresis. There are three states of the algorithm - initialize, peak search and valley search.
Rainflow counted cycles are typically used in low cycle fatigue damage analyses. The rainflow counting algorithm is based on the "one-pass" algorithm described in the paper Simple Rainflow Counting Algorithms, International Journal of Fatigue, January 1982, by D. Socie and S. Downing. The algorithm described in this paper generates the set of closed cycles for the input peak valley sequence, assuming that the sequence repeats itself.
However, to support proper "rainflow histogram addition" (that is, generating a composite rainflow histogram from multiple rainflow histograms defined in a specific sequence), the system stores both the sequence of unclosed reversals and the histogrammed set of closed cycles in the Rainflow DataMode.