Simulation of eddy current nondestructive testing problems with the CIVA software platform

Transcription

1 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 7th National NDT Conference of the Hellenic Society of Non- Destructive Testing Athens October

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 2

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 3

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 76 permanent positions 25 PhD students, Postdocs Average age : 35 Methods Examination of noisy materials Complex geometries Increase of productivity, Defect characterization, Waste, Concrete, Material ageing, 4

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 5

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 Description of canonical geometries using Green dyads Modelling of various types of coils and flaw configurations Series of fast calculations for parametric studies Variation plots ECT configuration defined within CIVA 6

7 The Volume Integral Method (VIM) Principle of ECT modeling with the Volume Integral Method: 3 steps Primary electric calculated in the unflawed W zone Calculation of the total electric field E in W Calculation of the probe response (reciprocity theorem) E 0 W W E E 0 E W Description of the interaction between the flaw and E 0 using Green dyads: 7

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 8

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 9

10 Imag [du] SG Tube Inspection in PWR Imag [du] Tube internal inspection using bobbin coils (two identical bobbin coils connected in differential mode) 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 f = 100 khz f = 500 khz Simul : V / Exp : V / Real [du] Simul : V / 151 Exp : V / Real [du] 10

11 SG Tube Inspection near Tube Support Plates 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 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 11

12 Support plate characteristics Thickness: 30 mm Outer diameter: 40 mm Material: Inox 304L: σ = 1.4 MS/m, μ r = 1 External Longitudinal Notch Thickness = 54%, Height = 10mm Validation for 3D notches Inspection Frequency: 240 KHz SP Circumferential Through-Notch Height = 0.113mm, opening = 82 Experimental Data Simulation SP 12

13 Electric field (Amp.) Phase Tube manufacturing (metallurgy) Inspection of ferromagnetic tubes Petrochemical industry Fast neutron reactor condensers Remote field eddy-current (RFEC) technique Near Field Trans. Zone Remote Field 13

14 Inspection of ferromagnetic tubes Extension of the VIM formulation to take into account the variation of the magnetic permeability Remote field inspection of a 50% external groove E R1 R2 A. Skarlatos et al., IEEE Tans. on Magn., vol. 44, pp ,

15 Inspection of riveted structures Layered structure Rivet FAA report: Destructive Evaluation and Extended Fatigue Testing of Retired Transport Aircraft (DOT/FAA/AR-07/22,V1) 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) Aircraft corrosion J. E. Stump, 15

16 VIM modelling of riveted multilayered structures Introduction of 2 finite zones in the stratified medium containing the rivet and the flaw ECT of flaw located at the bottom of a rivet E 1 E 2 s 1, m 0 s 2, m 0 2 layers (conductivities s 1 and s 2, magnetic permeability m 0 ) System of integral equations for electric fields E 1 and E 2 (non magnetic case) Excitation fields in the workpiece Green dyads calculated analytically 16

17 Flaw detection between two rivets Real part (mv) Imaginary part (mv) Real part (mv) Imaginary part (mv) E 4 E 2 E 5 E 1 E 3 C. Reboud et al., Electromagnetic Non-Destructive Evaluation (XIII), IOS Press, 2009, pp

18 Simulation of multiple interacting flaws VIM matrix formulation: Flaw 1 Flaw 2 Flaw 3 Perturbations of ECT signals due to additional flaws Transmitter Receiver Simulation of ECT signals due to flaws with complex shapes Single coil Probe scan Probe scan y y Flaw signature recovered by a stronger one Better description of realistic flaws x Amplitude of the ECT signal (mv) Amplitude of the ECT signal x (mv) 18

19 Real part (X channel) Imaginary part (Y channel) Effect of the probe tilt Lift-off: 0.5 mm 10 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, L X = 5 mm, L Y = 0.3 mm and L Z = 0.5 mm Loss of symmetry and signal amplitude roughly divided by a factor 2 in the tilted case C. Reboud, G. Pichenot, and T. Theodoulidis, Review of Progress in Quantitative Nondestructive Evaluation, 2008, pp Symmetric signal Loss of symmetry 19

20 Effect of the probe tilt Validation results: CIVA vs. experimental data Impedance variation due to the flaw Inconel plate s = 1 M.S/m, m r = 1, Thickness 1.55 mm EDM notch Surface-breaking Length 7 mm, Opening 0.1 mm, Depth 1.24 mm (80 %) Air-cored coil Int./ext radii: 1 mm / 1.8 mm, Height: 1.92 mm, Nb of turns: 360 lift-off: mm (constant) Frequency: 100 khz Agreement between simulation and experiment better than 18% in amplitude and 3 in phase 20

21 Reliability assessment of ECT procedures Simulation based POD calculations in an ECT case Introduction of statistical tools describing uncertainties Nominal value of the lift-off Variation of the probe lift-off Available distributions: uniform, normal, log-normal, exponential, Rayleigh Description with a normal distribution of values 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 21

22 Reliability assessment of ECT procedures Example: Behavior with respect to the flaw height, given some description of lift-off variations (bounded normal distribution) Parametric model of Probability of Detection (POD): Signal Response Definition of a detection threshold Parametric form: F(z): normal cumulative distribution function m and s estimated from calculated points 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 Lower bound confidence interval Characteristic value: here the flaw height 22

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 23

24 New challenges and development perspectives 8 m m Work under way: Introduction of a contrast of permeability in planar configurations: Modeling of magnetic fasteners and magnetic flaws Modeling of thin cracks with complex shapes Modeling of new sensors (GMRs, EMAT, flexible sensors on Kapton film, etc.) B y J x F z S N S N N S N S 100µ m Simulation of other NDT methods: e.g. Magnetic Flux Leakage 24