improved methods for magnetic silencing in ships and submarines. tim baynes
TRANSCRIPT
Improved Methods for Magnetic Silencing in
Ships and Submarines.
Tim Baynes
X Coil
Z Coil
Demagnetisation
3 Stage Deperm
-2000
-1000
0
1000
2000
0 150 300 450
Time (mins)
Ap
plied
Fie
ld (
A/m
) Stage 1 Stage 2 Stage 3
3 Stage Deperm
-2000
-1000
0
1000
2000
0 150 300 450
Time (mins)
Ap
plied
Fie
ld (
A/m
) Stage 1 Stage 2
3 Stage Deperm
-2000
-1000
0
1000
2000
0 150 300 450
Time (mins)
Ap
plied
Fie
ld (
A/m
) Stage 1
THE PROBLEM
1.Redundancy
2.Time consuming
3.Predicting deperm outcome
Anhsyteretic Deperm
-2000
-1000
0
1000
2000
0 450
Time
Ap
plied
Fie
ld
(A/m
)
-1
0
1
-2000 -1000 0 1000 2000H (A/m)
M/Ms
major hysteresisloop
anhysteretic
initial curve
Anhysteretic magnetisation
0
10
20
30
40
50
60
70
80
90
0 1000 2000 3000Applied Field (A/m)
Mre
m (kA
/m)
Anhysteretic
Anhysteretic theory
Theory and Experimental Results
for Laboratory Anhysteretic Deperms
Longitudinal magnetisation during deperm
-1
0
1
0 35 70
Shot Number
M lo
ngitudin
al
submarine long.tube long.
-1
0
1
0 35 70
Shot Number
Longitudin
al M
submarine long.
Final VM
0
50
100
150
200
250
0 50 100Number of Steps
(
A/m
)
Deperm Results
Preisach Model
-20
00
-16
00
-12
00
-80
0
-40
0 0
40
0
80
0
12
00
16
00
20
00 -2000
-1600
-1200
-800
-400
0
400
800
1200
1600
2000
a
b
P(a,b)
a = -b
Anhysteretic deperm on tube
-1.2
-0.8
-0.4
0
0.4
0.8
1.2
0 5 10 15 20 25
Shot number
M/M
sta
rttheorytube
Modelled Flash D deperm
-1.0
-0.5
0.0
0.5
1.0
0 20 40 60
Shot number
Lo
ng
itu
din
al M
/Mm
axtheorySteel tube
Complete Deperm
-1
-0.5
0
0.5
1
0 50
Shot number
M/M
Sta
rt
submarinetheory
Summary:• Laboratory simulation has allowed experiments
into alternative deperm procedures.• “Anhysteretic deperm” was QUICKER more
RELIABLE + allows for theoretical modelling.• Theoretical models have been used to describe
magnetisation changes in models and real vessels.
BOTTOM LINE: NEW DEPERM IS QUICKER, MORE RELIABLE and MORE PREDICTABLE
More information at: www.phys.unsw.edu.au/~tmb/downloads.htm
