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Difference between "Range-Mean" and "From-To" cycle counting

by Siemens Theorist Siemens Theorist on ‎03-08-2017 12:40 PM - edited

The unsymmetrical From-To cycle counting keeps more information about the loading cycles than Range-Mean counting does, because it also stores the "orientation" of each load cycle. This is important information if you want to reconstruct a time history from a Rainflow matrix.

 

The Rainflow counting of LMS Tecware is a From-To cycle counting, and thus the default representation of the Rainflow matrices are also in From-To form.

 

However, Tecware also allows changing the representation to Range-Mean matrices. In fact, a Range-Mean histogram can always be derived from a From-To histogram, but not vice versa. This is because the From-To representation includes additional information (as mentioned above).

 

Example:

Look at the two load histories below:time_hist.png

They both have the same mean level and the same number of cycles, and the cycles' amplitudes are identical. The only distinctive property is the opposite polarity.

 

from_to.png

 

Looking at the Rainflow matrices of the two load histories, we get in the From-To representation:

from_to_matrix.png

 

The Rainflow matrix of "Load_up" shows hanging cycles, whereas the corresponding Rainflow matrix of "Load_down" shows standing cycles.

The denotation hanging and standing is motivated from the stress-strain-path. There, a hanging event is connected to the superior hysteresis branch at its upper reversal point, but a standing event is connected at its lower reversal point.

 sig_eps.png

 

When a load cycle is just represented by its range and mean, the distinction between hanging andstanding is not possible. Thus, the Range-Mean representation for both of the signals looks like this:

 range_mean_matrix.png

 

Remarks:

The desired representation of a Rainflow matrix can be set in the "RainView layout" window, which is available via the menu Options à Layout within the Rainflow matrix display.

 

rain_view.png

 

Rainflow matrices can only be edited in the From-To representation. 

 

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