Instructions

UM-0085-B09 DT80 Range User Manual Page 80
RG
c..dIV IV Contents
Example:
21..40IV
c+0
Contains the count of cycles for the first cycle size class
21IV
c+1
Contains the count of cycles for the second cycle size class
22IV
c+2
Contains the count of cycles for the third cycle size class
23IV
⇓
⇓
⇓
d–7
Contains the count of cycles for the last cycle size class
33IV
Summary data
d–6
Contains the count of cycles that over-ranged the maximum cycle size
34IV
d–5
Contains the count of all cycles
35IV
d–4
Contains the maximum buffered cycles 0..100 (or 99999 if the buffer has overflowed and
buffered half-cycles have been lost)
36IV
d–3
Contains the minimum valley encountered
37IV
d–2
Contains the maximum peak encountered
38IV
d–1
Contains the total number of good points
39IV
d–
0
Contains the total number of "in error" points (out of range, for example)
40IV
In practice, some cycles do not close immediately and are buffered until a closure is detected. Variable d–4 contains a
count of these unclosed or "half cycles".
Note: The rainflow channel option can be used on a maximum of 16 channels.
Rainflow cycle data is collected at a rate dependent on the frequency of influences deforming the structure under test.
These might be quite slow events (such as waves crashing against a sea wall), or quite fast (such as a high speed boat
hull travelling through waves).
Place the channel being sampled for rainflow in a schedule that’s triggered fast enough to take sufficient readings during
a cycle to adequately characterise the loop closures. For example, the schedule
RA50T 3BGI(RAINFLOW:a:b:c..dIV,W)
measures the input every 50ms (20 times/sec), and counts loop closures. The W channel option declares this as a
working channel (does not return or log the individual samples of strain-stress.
Reporting Rainflow Data
Rainflow data is collected over long periods of time using the RAINFLOW channel option. Then, periodically, the rainflow
cycle histogram can be retrieved by a computer, using the
RAINFLOW command.
To report the rainflow cycle histogram, send the original rainflow channel option exactly as originally defined for the
channel, but as a command. That is, send the command:
RAINFLOW:a:b:c..dIV
The DT80 returns a tabular report as illustrated below:
RAINFLOW:72:5:1..27IV
Rainflow ( 5% rejection) 01/01/2000 00:03:43
n IV/CV Range Mean Cycles
==============================================
1 1 0.0 0.0 0
2 2 3.6 11.4 27
3 3 7.2 11.3 6
4 4 10.8 12.4 6
5 5 14.4 11.9 6
6 6 18.0 12.8 9
7 7 21.6 12.3 2
8 8 25.2 0.0 0
9 9 28.8 0.0 0
10 10 32.4 0.0 0
11 11 36.0 18.0 1
12 12 39.6 0.0 0
13 13 43.2 0.0 0
14 14 46.8 0.0 0
15 15 50.4 0.0 0
16 16 54.0 0.0 0
17 17 57.6 0.0 0
18 18 61.2 0.0 0
19 19 64.8 0.0 0
20 20 68.4 0.0 0
21 21 >= 72.0 0.0 0
==============================================
Total cycles 58
Peak/Valley mean 12.6
Max Peak 71
Min Valley -1
Max buffered cycles 11
Valid input points % 100.00