Structural Health Monitoring anStructural Health ......BHN-Para 0.3 2500 3000 3500 4000 4500 5000 5500 6000 6500-0.5-0.4 0 Magnetic feld 04-0.3-0.2-0.1 0.0 0.1 Width of the peak Atfthk

1

Structural Health Monitoring anStructural Health Monitoring an Großanlagen unter Anwendung von

Multisensorsystemen undMultisensorsystemen und fraktalbasierten Auswerteverfahren

Jürgen Schreiber

h f i fFraunhofer Institut fürZerstörungsfreie Prüfverfahren

Institutsteil Dresden

Sensorsysteme 2008 Lichtenwalde, 16-18. Oktober 2008

2Introduction

Challenge:

Save and economic service of

Characterisation of the material damage state without baseline

Save and economic service of safety relevant industrial components

Maximal usage of the whole Reliable evaluation of the fatigue gservice life time, definition of actions

gdamage , forecasting of the residual life time

Search for suitable NDT-methodseither for

regular inspection

Structural Health Monitoring

or


3Introduction

Fatigue Monitoring in nuclear power plants

Up to 150

AREVAErlangenp

thermocouples in 20-50 measurement sectionsplus signals of existing p g goperational instrumentationfor residual life timeestimationestimation

Materials damage Safty


4Introduction

Components of brown coal open cast mining

Vattenfall EuropeC ttb

Cyclic load

CottbusSystem of strain gauges are displaced to control load and

h

Aging

to assess the service strength

Materials damage Residual service life time ?Materials damage Residual service life time ?


5Introduction

Materials damage Actions?


6Introduction

Integrity of Railway Structures Wiener Linien

strain

gauge

Tests with mobile eddy current sensor system for crack inspection

Rolling Contact Fatigue Repairing in time before cracking


7Introduction

Available NDT-methods

• Micro-thermography: Crack indicator, but too week signals from deformation structure

• US-backscattering: Multiple scattering and long propagation path strongly mask the effect of deformation meso-structures, while cracks are seen well.

• Acoustic emission: Low effect of plastic deformation, signals only due to force changes

P t ti l W k iti it f d f ti l k• Potential sensor: Weak sensitivity for deformation, only crack indication

• Optical methods: Dirty surface prevent simple application • Eddy current: Good for crack indication but deformation?• Eddy current: Good for crack indication, but deformation?• Barkhausen noise: Testing locally, simple and continuous noise

excitation, magnetic parameters sensitive to stress and microstructureand microstructure.

What can we learn from standard Barkhausen noise measurements?


8State of the art in NDT

l b ( )

Barkhausen noise parameter versus fatigue

Material: 15NiCuMoNb5 (WB 36)

250

300

a] m/m

]

100

125

250

ess

σ xx

[MP

stic

str

ain

[µ

50

75

resi

dual

str

ey

[a.u

.], p

las

stress controlled (R=0; f=3 Hz, stop at necking)

0

25

load

, B

Hx,

BHstop at necking)

a) N=0-1000, σa=240MPa

b) N=1000-2000, σa=260MPa0 1000 2000 3000 4000 5000 6000 7000

number of cyclic load Nc) N=2000-6000, σa=260MPa

c) N=6000-6229, σa=300MPa


9State of the art in NDT

0.20.3

150

Barkhausennoise-Signal

Barkhausen noise parameter versus fatiguem

eter

-0 4-0.3-0.2-0.10.00.1

Integrated sumRMS 50

100

0.20.3

BH

N-P

aram

2500 3000 3500 4000 4500 5000 5500 6000 6500

-0.5-0.4 RMS

0

50

Magnetic feld

0 4-0.3-0.2-0.10.00.1

Width of the peakA t f th k

0 500 1000 1500 200050

Time [µs]

2500 3000 3500 4000 4500 5000 5500 6000 6500

-0.5-0.4 Asymmetry of the peak

Number of cyclic load N

This method is not able to estimate the actual stage of fatigue!

Resume:


10New developments in NDT for SHM

Thermocouples

Mounting StrapMounting StrapCover shell

Multi-sensor systems to detect ti h t i ti f

Sm - magnetizing coilsDS - detecting sensors for

Barkhausen noise

time characteristics of materials response to

thermo-mechanical load



Concept of 16-element eddy current line array developed

at IZFP-Dresden.

Schematic of 64-element two-dimensional eddy current array planned

as foil sensor systemy

Array sensor system to detect St t l i dd tStructural varying eddy current

(“Grain noise”)



Scheme of fibre Bragg grating sensor (see IPHT, Bartelt)

Meander type fiber Bragg grating sensor system for

space time characteristics of loadspace-time characteristics of load as well as

materials damage


13

Mesoscopic deformation structures

It is possible now to measure very much, however, what is the key information for the assessment of materials damage?

Micro M MMicro Meso Macro

Panin-Idea:

CT-Image of fatigue crack

Mesomechanics

TEM-Image

Eine wirklich gute Idee erkennt man daran, dass ihre Verwirklichung von vorneherein

ausgeschlossen erscheint.g

Albert Einstein (1879 - 1955)


14


Austenitic sample Ferritic sample

a) b)

c)

a) N = 2000, b) N = 7000, c) N = 13000

)

What does characterise these structures?


15


Theoretical und experimental basis

Mesomechanics (Panin since 82) Depinning Models ( self-organising criticality“ 90ies)Plastic deformation: Gliding locally due to stress concentrators accompanied by

i f i hb i i

(avalanches, sand pile, domain motion)Distribution of jump heights, duration and energyas well as the power spectrum for Barkhausen noise in

hrotation of neighbouring grains formation of closed structures

(new structure elements) hierarchical structure

amorphous magnets:

D(s) ~ sα , P(k) ~ k β scaling behaviour

Symmetry arguments point at 3 universal classes:hierarchical structure•Dislocation pattern (Micro)• Slip band formation (Meso I)• Folded multi-bands (Meso II) S i

Symmetry arguments point at 3 universal classes:

• α 1 ≈ 1.70 ⇒ 3D domains , dipole-dipole-interaction• α 2 ≈ 1.44 ⇒ 2D domains in local fields• α 3 ≈ 1 30 ⇒ 2D multi-domains in local fields

Suggestion:Scaling behaviour of micro-meso-structure may characterise fatigue, fractal dimension DF as a

α 3 1.30 ⇒ 2D multi domains in local fields

However, continuous transformation between the structures are obtained experimentally. There are similarities between deformation and fatigue, fractal dimension DF as a

measure of damage? magnetic structures!

Scaling behaviour


16


Scaling behaviour?

150

.]

50

100

usen

noi

se si

gnal

[a.u

.

0 500 1000 1500 200050

0

time [µs]

Bar

khau

Topography Z(Ri) or time signal S(t) Z(λRi) ~ λH Z(Ri) i i

S(λti) ~ λH S(ti)Fractal dimension: DF

(r) = 3- H(R) or D(t)F = 2 – H(t) ,

Area length: F(s) s H-1Area, length: F(s) ~ s H 1, Correlation function: C(τ) = <|S(t+ τ)-S(t)|2>t ~ τ 2H


17


Load direction

FOnline SEM-Images

X6 CrNiTi 18 10Panin, Kuznetsov, Schreiber (1998)

σa ~ 240, 250, 260 MPa

ΔD = 0 04ΔD = 0 07 B

ΔDF32 = 0.04ΔDF21 = 0.07

What is a suitable NDT-method?


18

Mesoscopic deformation structuresTopography and micro-magnetic structures

N =622AFM-Topography N = 622, DF = 2.53Fatigue experiment

0 7 % d /d 3 %/ i

15 NiCuMoNb 5

N=0εa = 0.7 %, dε /dt = 3 %/min

M t tMesostructures

MFM-Image DF = 2.50


19Fractal analysis of Barkhausen noise

150

]

Magnetic Barkhausen noise

50

100

ise

sign

al [a

.u.

680 685 690 695 700

0

50

Bar

khau

sen

nof ld

0 500 1000 1500 200050

time [µs]

BMagnetfeld

Integral parameters1. Integrated Amplitude 2. RMS-value3 ( )

Time series1. Distribution of chumps2. Powerspectrum

3. Asymmetry (Moments) 3. Correlation function



30

40

50Simulation of real fractals:

Finite time series and random noise

Snowflake + noise

10

20

Cq r( )N r−

Si r+ Si−( )q

N r−∑:=S

0 100 200 300 40010

01i =

15 1 5

Time [µs]Analysis for the integrated time series

101

1.5

Cq(r)q = 3

5

0.5

Snowflake - exactDF = ln4/ln3 = 1.262Fit ~ r a

DF = 2-a/q

0.1 1 10 100 1 .103 0 10 20 30 40 500

qTime difference r [µs]



Online fatigue experiments(variable strain amplitude and strain rate) 15 NiCuMoNb 5

440

472

503

534

566

Last

max [M

Pa]

and strain rate) 15 NiCuMoNb 5

1,40

1,45

1,50

Probe 342 ε

α = 1.2%, dε/dt = 12%/min

Probe 354n

377

409

440

log(N/NA)

1 20 15 NiCuMoNb 5 (WB36), dε /dt = 12 %/min, R = -1)

1,15

1,20

1,25

1,30

1,35 Probe 354ε

α = 1.0%, dε/dt = 12%/min

Probe 365N

B = 348, ε

α = 1.2%, dε/dt = 6%/min

rakt

ale

Dim

ensi

on

1.15

1.20 15 NiCuMoNb 5 (WB36), dεa/dt 12 %/min, R 1) εa = 0.4 % bis N = 2000 (NB ~ 45000) εa = 1 % bis N = 2315 (NB ~ 2500)

X6 CrNiTi 18 10 (online, REM) f 2H 250MP R 0)m

ensi

on D

F

-3,5 -3,0 -2,5 -2,0 -1,5 -1,0 -0,5 0,0 0,51,00

1,05

1,10Fr

log(N/NB)

1.05

1.10f=2Hz, σa ~ 250MPa, R

σ=0)

Frak

tale

Dim

gB

ΔDF(1 2) = 0.082 (Topografie: 0.07) ΔDF(2 3) = 0.045 (Topografie: 0.04) -5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5

1.00

log(N/NB)



1.20Effect of cracks on DF

Riss

1.10

1.15

men

sion

120

1.00

1.05

S üb Ri

Frak

tale

Di

100

80

1.0 1.5 2.0 2.5 3.0 3.5

0.95Scan über Riss

Scan 90° versetzt

Position [mm]

80

60

40

Computer-Tomography


23Applications

22 NiMoCr 37Y

RMS R id l

CT-samplelike a component

RMS ~ Residual stress Fractal dimension

crack121.4

1.5Fractal d

X

0

1

6

8

10

4

RMS

X

0

1

1.1

1.2

1.3

1.4

4

dimension D

F

X

2

3

4

-4

-2

0

2

4

Y-Ach

se [c

m]

X-Achse [cm]

1

2

3

4-2

0

2

4

Y-Ach

se [c

m]

X-Achse [cm]

45

55

-4

2

3

4-4

-3-2

-10

12

34

Y-Ach

seX-Achse Asymmetry parameter


24

Applications

Brown coal open cast mining

Support of the 600 m long bridge F60 pp g g


25

RissR120 RissR80 RissR120 RissR80

Along the crack Perpendicular direction

Applications

2

1

sitio

n

1.139

1.166

1.194

1.221

1248

Riss R120 Riss R80DF

2

11.139

1.166

1.194

1.221

1.248

Riss R120 Riss R80DF

DF

4 6 8 10 12 14 16 18 205

4

3

y-P

os

1.248

1.275

1.303

1.330

1.357

4 6 8 10 12 14 16 18 205

4

31.275

1.303

1.330

1.357

Riss R120 RissR80 Riss R120 Riss R80

F

3

2

1

ositi

on

2.080

3.105

4.130

5.155

6.180

Riss R80RMS [r.E.]

3

2

1

RMS [r.E.]

2.080

3.105

4.130

5.195

6.108

RMS

4 6 8 10 12 14 16 18 205

4

3

y-P

o

P i i

7.205

8.230

9.255

10.28

4 6 8 10 12 14 16 18 205

4

3

y

7.205

8.230

9.255

10.28

Riss R120 Riss R80RMS[rE]

Riss R120 Riss R80

Beginning cracks?

3

2

1

ositi

on

191.0

234.5

278.0

321.5

365.0

RMS [r.E.]

3

2

1

Asym[r.E.]

191.0

234.5

278.0

321.5

365.0AsymFatigue

versus

4 6 8 10 12 14 16 18 205

4

3

y-P

o

x-Position

408.5

452.0

495.5

539.0

4 6 8 10 12 14 16 18 205

4

3

x-Position

408.5

452.0

495.5

539.0

versus power crack?


26Applications

First results for “Wiener Linien” rails

Y

X

Y ~ roling direction

Io : 70 120


27Applications

1.5

1.6

1.7in service

lina Aline B

PerpendicPerpendicular directionRMS ~ Residual stress

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4 line B

new line A line B

MS

~ R

esid

ual s

tres

s

A1 A2 A3 A4 A5 A60.2

0.3

0.4

0.5

0.6

Measuring position

RM

Roling d

2.2

2.4 in servicelina A

Roling direction

1 0

1.2

1.4

1.6

1.8

2.0

lina A line B

new line A line B

MS

~ R

esid

ual s

tres

s

A1 A2 A3 A4 A5 A60.2

0.4

0.6

0.8

1.0

RM

Measuring position


28Applications

1.40

Perpendicular direction1.40

DF ~ Fatigue damage

1 20

1.25

1.30

1.35

tale

Dim

ensi

on D

F

line A line B

1.20

1.25

1.30

1.35 line A line B

tale

Dim

ensi

on D

F

ewervi

ce

1 2 3 4 5 61.10

1.15

1.20

Frac

tMeasuring Position

1 2 3 4 5 A61.10

1.15

Frac

t

Measuring Position

ne

in s

e

Roling direction

1 35

1.40

line A

1.40

line A

1.20

1.25

1.30

1.35 line A line B

acta

le D

imen

sion

DF

1.20

1.25

1.30

1.35 line A line B

ract

ale

Dim

ensi

on D

F

1 2 3 4 5 6

1.10

1.15Fra

Measuring Position1 2 3 4 5 6

1.10

1.15

Fr

Measuring Position


29Further applications


30Further applications

Fractal dimension of Barkhausen noise

1 35

1.40 Neu Gebraucht 9.0

Sample A1.20

1.25

1.30

1.35al

dim

ensi

on

7.0

7.5

8.0

8.5

RMS RMS

MS

1.05

1.10

1.15Frac

ta

5.5

6.0

6.5

RM

1.0 1.5 2.0 2.5 3.0 3.5 4.01.00

Messpunkt

1 2 3 4 55.0

Messpunkt

1.30

1.35

1.40

n DfNeu 5.4

5.6

5.8

6.0

DfNeu DfGebrau

1.15

1.20

1.25

30

Frac

tal d

imen

sio DfGebraucht

4.2

4.4

4.6

4.8

5.0

5.2

RM

S1.0 1.5 2.0 2.5 3.0 3.5 4.0

1.00

1.05

1.10

1.0 1.5 2.0 2.5 3.0 3.5 4.0

3.4

3.6

3.8

4.0

Sample B


31Outlook

τ = -log(N/NB) Estimation of residual life

1.20

1.25

DF(N

/NB)

Dm

DF(N/NB)-function independent on NB and R universal curve! 1.10

1.15

ract

al d

imen

sion

D DmF

NB and R universal curve!

-3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.51.05

1.10

Life time parameter −τ

τm

Fr

DMS Load collectives +Wöhler-curve NB, α(Δti) = ΔN(Δti)/Δti

mM(m)B

m mi 1 i

NT 1/M(m) (1 exp( ))( t )=

= − −τα Δ∑

Residual service life time


32Outlook

Ti l d S kl Ph

Nonmagnetic materials

Time resolved Speckle-Photometry

He-Ne laser

CCD camera

He-Ne laser

CCD camera

CO2 laser heatingImaging Optics

S kl

CO2 laser heatingImaging Optics

S klSpecklesSpeckles

1.6

1.7

Al-alloyF

Thermal waveThermal wave

1.1

1.2

1.3

1.4

1.5

al d

imen

sion

DF

0.01 0.1 10.8

0.9

1.0

1.1

Frac

ta

log(N/NB)


33Outlook

Fractal dimension DF as a function of running time

y 3 000 MPa, T = 60 °C

Direction x-axesalong roling

trace

y-axesx

100 h 1.059 1.18

200 h 1.129 1.083

300 h 1.37 1.265

400 h 1.126 1.349


34Outlook

<j(t)> = <j(to> – (<j(to>- <j(t ∞)) (1 – R(t-to))R(t t ) Δj(t) Δj(t ) / Δj2 d Δj(t) j(t) j(t )

Eddy current relaxation

R(t-to) = <Δj(t) Δj(to)>/< Δj2> and Δj(t) = j(t) - j(t ∞)

Pos 2

Pos 3

Pos 4Pos 2

Pos 3

Pos 4

Pos 1Pos 4.1

Pos 4.2Pos 1Pos 4.1

Pos 4.2


35Conclusion

SHM – characterization of materials damage before cracking and without baseline!Fractal analysis of deformation structure new working concept based on DF!

For steel DF increases with fatigue damage, however, the appearance of cracks and the stress release can locally reduce DF.

as a function of cyclic load number was found.Symmetry arguments point at the existence of three universality classes.

The fractal analysis of the offers the possibility to introduce the fractal concept into the inspection practise. Besides of DF the RMS-value of Barkhausen noise has to be measured in order for crack indication

Search is ongoing for similar approach to nonmagnetic materials (eddy current noise, Speckle-Photometry), it looks promising!

IZFP is now developing a special device “FrakDim” with optimized working regime including fast soft ware. Specialized sensors will be manufactured.


36

Than you very much !


Documents

Structural Health Monitoring anStructural Health ......BHN-Para 0.3 2500 3000 3500 4000 4500 5000 5500 6000 6500-0.5-0.4 0 Magnetic feld 04-0.3-0.2-0.1 0.0 0.1 Width of the peak Atfthk