MTS Series 793 Application - Manual (Page 320)

MTS MultiPurpose TestWare®
Fatigue Process
Data Acquisition Process Descriptions 320
About Rainflow Counting and Histograms
Rainflow counting Rainflow counting is a method of concisely representing the cyclic content of a
signal. It is used to reduce large amounts of data to a more usable form by
creating one-pass histograms from drive or response signals. Strain ranges for
closed stress-strain hysteresis loops are recorded, and then fatigue life predictions
can be made using the strain range and the associated number of closed cycles.
The following example illustrates rainflow counting of a simple strain time
history using the Range histogram method. The associated stress-strain response
is also shown.
Histogram types
Rainflow-counted histograms provide a means for summarizing the cycles that
are identified by rainflow counting. A histogram is created by using data
compression to reduce large amounts of data into blocks of information (bins).
Each histogram bin contains a cumulative count for data occurrences within a
specified bin range.
The Fatigue process provides three histogram types: RangeMean, Range, and
MaxMin.
A description of each type appears below. For purposes of illustration, the local
stress/strain hysteresis response is used to show the methods for creating
histograms.