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7th National NDT Conference of the Hellenic Society of Non-
Destructive Testing
Athens 15-17 October 2010
Simulation of eddy current nondestructive
testing problems with the CIVA software
platform
A. Skarlatos, G. Pichenot, C. Reboud, D. Prémel and S. Mahaut
CEA LIST, France
http://www-civa.cea.fr
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 2
Outline
• Activities of CEA LIST in the field of NDT
• ECT module presentation:
The Volume Integral Method (VIM) formulation
• Applications
• Steam generator tube inspection
• Inspection of riveted planar multilayered structures
• Simulation of realistic flaws
• Modelling of the tilt effect
• Reliability assessment of ECT procedures using simulation supported
Probability of Detection (POD) calculations
• New challenges in the ECT modelling and perspectives of the CIVA
platform development
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 3
Outline
• Activities of CEA LIST in the field of NDT
• ECT module presentation:
The Volume Integral Method (VIM) formulation
• Applications
• Steam generator tube inspection
• Inspection of riveted planar multilayered structures
• Simulation of realistic flaws
• Modelling of the tilt effect
• Reliability assessment of ECT procedures using simulation supported
Probability of Detection (POD) calculations
• New challenges in the ECT modelling and perspectives of the CIVA
platform development
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 4
Activities of CEA LIST in the field of NDT
NDT Simulation
Development of the CIVA platform:
• UT, ECT, RX
• Signal processing
• Reconstruction
• Analysis tools
Instrumentation
• Development of adaptive flexible
probe arrays
• Study of new technologies
of detectors
Methods
• Examination of noisy materials
• Complex geometries Increase of
productivity,
• Defect characterization, Waste,
• Concrete, Material ageing, …
76 permanent positions
25 PhD students, Postdocs
Average age : 35
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 5
Outline
• Activities of CEA LIST in the field of NDT
• ECT module presentation:
The Volume Integral Method (VIM) formulation
• Applications
• Steam generator tube inspection
• Inspection of riveted planar multilayered structures
• Simulation of realistic flaws
• Modelling of the tilt effect
• Reliability assessment of ECT procedures using simulation supported
Probability of Detection (POD) calculations
• New challenges in the ECT modelling and perspectives of the CIVA
platform development
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 6
The ECT module of the CIVA platform
• Semi-analytical models for ECT simulation
based on the Volume Integral approach
• User interface oriented toward ECT
applications: few numerical parameters
ECT configuration defined within CIVA
• Description of canonical geometries using
Green dyads
• Series of fast calculations for parametric
studies
Variation plots
• Modelling of various types of coils and flaw
configurations
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 7
Principle of ECT modeling with the Volume Integral Method: 3 steps
W
E0
Primary electric calculated
in the unflawed W zone
W
Calculation of the total
electric field E in W
Description of the interaction between
the flaw and E0 using Green dyads:
E
The Volume Integral Method (VIM)
W
Calculation of
the probe response
(reciprocity theorem)
E0
E
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 8
Outline
• Activities of CEA LIST in the field of NDT
• ECT module presentation:
The Volume Integral Method (VIM) formulation
• Applications
• Steam generator tube inspection
• Inspection of riveted planar multilayered structures
• Simulation of realistic flaws
• Modelling of the tilt effect
• Reliability assessment of ECT procedures using simulation supported
Probability of Detection (POD) calculations
• New challenges in the ECT modelling and perspectives of the CIVA
platform development
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 9
SG Tube Inspection in PWR
• Internal inspection using axial and
rotating coils in (helicoidal scan)
• Inspection of the tube bundles
between and near Tubes Support
Plates (TSP)
• Small tube diameters (~20 mm)
• Inspection of large distances along
the tubes
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 10
• Calibration based on the signal of 1 mm
through-hole
• Inspection of a transversal through-notch of
0.13 mm opening and 82° angular extension
Simul : 0.301 V / -17.4°
Exp : 0.3033 V / -18.5°
Real [dU]
Imag
[dU
]
Real [dU]
Imag
[dU
]
Simul : 0.2905 V / 151°
Exp : 0.2907 V / 148.8°
f = 100 kHz f = 500 kHz
Tube internal inspection using bobbin coils
(two identical bobbin coils connected in differential mode)
SG Tube Inspection in PWR
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 11
SG Tube Inspection near Tube Support Plates
Primary field calculation for the
tube + TSP structure (FEM)
Flaw interaction in tube without the
TSP (VIM)
Probe response with FEM primary
field + VIM flaw interaction
• Need for simulation of TSP of complex
shapes (trifoliate and quadrifoliate)
usually employed in commercial PWR
facilities
• Complete FEM simulations are
computational demanding
Use of a combined FEM-VIM approach
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 12
Validation for 3D notches
Experimental Data
Simulation
Inspection Frequency: 240 KHz
• External Longitudinal Notch
Thickness = 54%, Height = 10mm
SP
• Circumferential Through-Notch
Height = 0.113mm, opening = 82°
SP
Support plate characteristics
Thickness: 30 mm
Outer diameter: 40 mm
Material: Inox 304L: σ = 1.4 MS/m, μr = 1
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 13
• Remote field eddy-current (RFEC) technique
Ele
ctr
ic fie
ld (
Am
p.)
Near Field Remote Field Trans.
Zone
Phase
Inspection of ferromagnetic tubes
Fast neutron reactor
condensers
Tube manufacturing (metallurgy)
Petrochemical industry
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 14
E
R1 R2
Remote field inspection of a 50% external groove
Extension of the VIM formulation to take into account the variation of
the magnetic permeability
Inspection of ferromagnetic tubes
A. Skarlatos et al., IEEE Tans. on Magn., vol. 44, pp. 623-632, 2008
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 15
Inspection of riveted structures
Fatigue damage of riveted structures
• Multiple cracks initiating at rivets location
• Defects buried in different layers of the structure
• Flaws signals small compared to rivets signals
Corrosion of aircraft structures
Exposed Under paint • Galvanic Corrosion (contact between
dissimilar metals)
• Intergranular Corrosion (aluminum alloys
and stainless steels)
• Filliform Corrosion (deterioration under
organic coating)
Rivet
Layered structure
Aircraft corrosion J. E. Stump, http://www.asnt.org/
FAA report: Destructive Evaluation and
Extended Fatigue Testing of Retired Transport
Aircraft (DOT/FAA/AR-07/22,V1)
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 16
Excitation fields
in the workpiece
Green dyads calculated analytically
• Introduction of 2 finite zones in the stratified
medium containing the rivet and the flaw
2 layers
(conductivities s1
and s2, magnetic
permeability m0)
s1 , m0
s2 , m0 E2
E1
• System of integral equations for electric fields E1 and E2 (non magnetic case)
ECT of flaw located
at the bottom of a rivet
VIM modelling of riveted multilayered structures
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 17
Real part (mV) Imaginary part (mV) Real part (mV) Imaginary part (mV)
Flaw detection between two rivets
C. Reboud et al., Electromagnetic Non-Destructive Evaluation (XIII), IOS Press, 2009, pp. 129-136.
E2
E1 E3
E5
E4
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 18
Simulation of multiple interacting flaws
Transmitter
Receiver
Probe
scan
Perturbations of ECT signals
due to additional flaws
x
y
Amplitude of the ECT signal (mV)
Flaw signature
recovered by
a stronger one
Single coil
Probe scan
Simulation of ECT signals due
to flaws with complex shapes
x
y
Amplitude of the ECT signal (mV)
Better description
of realistic flaws
VIM matrix formulation: Flaw 1
Flaw 2
Flaw 3
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 19
Effect of the probe tilt
10°
Loss of symmetry and signal amplitude
roughly divided by a factor 2
in the tilted case
Loss of symmetry
Frequency: 200 kHz
Plate: conductivity = 18 MS/m
thickness = 2 mm
Coil: inner and outer radii = 1 mm and 1.25 mm
height: 1 mm
Flaw: parallelepipedal notch,
LX = 5 mm, LY = 0.3 mm and LZ = 0.5 mm
Lift-off: 0.5 mm
Real part
(X c
hannel)
Imagin
ary
part
(Y c
hannel)
Symmetric signal C. Reboud, G. Pichenot, and T. Theodoulidis, Review of Progress in
Quantitative Nondestructive Evaluation, 2008, pp. 1915-1921.
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 20
Validation results: CIVA vs. experimental data
Impedance variation due to the flaw
Agreement between simulation and experiment better than
18% in amplitude and 3° in phase
• Inconel plate
s = 1 M.S/m,
mr = 1,
Thickness 1.55 mm
• Air-cored coil
Int./ext radii: 1 mm / 1.8 mm,
Height: 1.92 mm,
Nb of turns: 360
lift-off: 0.155 mm (constant)
Frequency: 100 kHz
• EDM notch
Surface-breaking
Length 7 mm,
Opening 0.1 mm,
Depth 1.24 mm (80 %)
Effect of the probe tilt
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 21
• Propagation of uncertainties with the semi-analytical model
N lift-off values generated
with a normal distribution
N simulations N results
Extraction of some
characteristic value
from each result
• Introduction of statistical tools describing uncertainties
Variation of the probe lift-off
Description with a normal
distribution of values
Nominal value of the lift-off
Available distributions:
uniform, normal, log-normal, exponential, Rayleigh
Reliability assessment of ECT procedures
Simulation based POD calculations
in an ECT case
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 22
• Parametric model of
Probability of Detection (POD):
Signal Response
Berens, A.P. (1988), “NDE Reliability Data Analysis”, ASM Metals
Handbook, Volume 17, 9th Edition: Nondestructive Evaluation and
Quality Control, ASM International, Materials Park, Ohio, 1988, pp.
689-701
Definition of a detection threshold
F(z): normal cumulative distribution function
Parametric form:
m and s estimated from calculated points Lower bound
confidence interval
Characteristic value: here the flaw height
Reliability assessment of ECT procedures
• Example: Behavior with respect to
the flaw height, given some
description of lift-off variations
(bounded normal distribution)
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 23
Outline
• Activities of CEA LIST in the field of NDT
• ECT module presentation:
The Volume Integral Method (VIM) formulation
• Applications
• Steam generator tube inspection
• Inspection of riveted planar multilayered structures
• Simulation of realistic flaws
• Modelling of the tilt effect
• Reliability assessment of ECT procedures using simulation supported
Probability of Detection (POD) calculations
• New challenges in the ECT modelling and perspectives of the CIVA
platform development
7th National NDT Conference of ΕΛΕΜΚΕ, 15-17 October 2010, Athens 24
• Introduction of a contrast of permeability in planar configurations: Modeling
of magnetic fasteners and magnetic flaws
New challenges and development perspectives
• Modeling of thin cracks with complex shapes
• Simulation of other NDT methods: e.g. Magnetic Flux Leakage
• Modeling of new sensors (GMRs, EMAT, flexible sensors on Kapton film, etc.)
N
S N S N
S N S xJ
yB
zF
•8 •m
•m
100µ
m
Work under way: