Campbell 21X Manuale dell'Operatore Scaricare il pdf (Pagina 127)

SECTION

11.

OUTPUT PROCESSING

INSTRUCTIONS

The

output flag

must be

set each

time

Instruction

80 is

used.

Instruction

80 must

directly follow

the instruction

that

sets the output

flag.

PAR. DATA

NO. TYPE

DESCRIPTION

01: 2

Storage area

option

o'

=

:ll3'o?',:'f,

f i"(Pi.:i'o

*

Storage)

03

=

Input

Storage Area

Q2: 4

Starting input location

destination

if

option

03

Output Array lD

if options 0-2

(1-511

are valid lDs)

***

81 RAINFLOW HISTOGRAM

***

The

Rainflow Instruction implements

the rainflow

counting algorithm,

essential to estimating

cumulative

damage fatigue to components

undergoing

stress/strain cycles. Data can

be

provided

by making measurements in

either the

standard or the

burst

mode. The

Rainflow

Instruction can

process

either a

swath

of data

following the burst

mode,

or it

can

process

"on

line"

similar to other

processing

instructions.

The

output is a two

dimensional Rainflow

Histogram

for each

sensor

or repetition.

One

dimension is the

amplitude of the closed

loop

cycle

(i.e.,

the distance between

peak

and

valley); the

other dimension is the mean of

the

cycle

(i.e.,

[peak

value + valley

value]/2). The

value

of

each

element

(bin)

of the histogram

can

be either the actual number of

closed

loop

cycles that had

the amplitude and

average

value

associated

with

that bin or the fraction

of the

total number of

cycles counted that

were

associated with

that bin

(i.e.,

number of cycles

in

bin divided by

total number of cycles counted).

The

user enters

the number of mean bins, the

number of

amplitude bins, and

the upper and

lower limits of

the input data.

The

values for the

amplitude bins are

determined by difference

between

the

upper

and

lower limits on

the input data and

by

the number

of

bins.

For

example, if the lower

limit is 100

and

the

upper limit

is

150,

and

there

are

5

amplitude

bins, the maximum

amplitude is 150

-

100

=

50. The

amplitude change

between

bins

and

the

upper

limit

of

the

smallest

amplitude

is

50/5

=

10.

Cycles with

an amplitude, A, less

than 10

willbe

counted

in

the first

bin.

The

second bin is for

10

< A

<

20,

the third

for

20 < A <

30, etc.

In determining

the ranges for mean bins,

the

actual

values

of the limits as well

as

their

difference are important. The

lower

limit

of

the

input

data

is also

the

lower limit

of the

first

bin. Assume

once again that the lower limit is

100,

the

upper

limit 150, and that

there

are 5

mean

bins. In this

case

the first

bin

is for

cyc

which

have a mean value, M, 100

<

M

<

110,

second bin 110

<

M

<

120.

etc.

lf

Cma

is

the count for

mean

range

m

and

amplitude range a,

and

M

and N

are

the

of mean and amplitude bins respectively; then

the output of one repetition

is

arranged

sequentially

as

(C1,1,

C1,2, ...

C1,N,

C2,1, C2,2, ..

Cr'r.ru).

Multiple

repetitions are sequential

in

memory. Shown in

two

dimensions, the output

is:

cr,r

Qz,t

c.r,z

cz.z

ct,r.t

cz,tt

Ct',1,t Cu,z cu,ru

The histogram can have either open or closed

form.

In

the

open form,

a cycle

that

has an

amplitude

larger

than

the maximum

bin

is

counted

in the maximum bin;

a cycle

that has

a

mean value

less

than the

lower

limit or

greater

than

the

upper limit is counted in

the

minimum

or

maximum

mean

bin.

In the

closed

form. a

cycle

that

is beyond

the

amplitude

or

mean

limits is

not

counted.

The

minimum distance

between

peak

and

valley,

Parameter 8, determines the

smallest

amplitude cycle

that

will be counted. The

distance should be less than the amplitude bin

width

([high

limit

-

low

limit]/

no. amplitude bins)

or cycles

with

the amplitude of the

first bin will

not

be counted. However,

if

the value

is

too

small,

processing

time

will be

consumed

counting

"cycles"

which are in reality

just

noise.

11-6

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