UT inspection of welding joins: issues and contribution of CIVA simulation tools

Transcription

1 UT inspection of welding joins: issues and contribution of CIVA simulation tools

2 GENERAL CONTEXT: ISSUES AND PROBLEMS OF WELD INSPECTION BY ULTRASONIC METHODS 67 th IIW Annual Assembly and International Conference Pierre CALMON 2

3 CONTEXT: NDT OF WELDING JOINS Kind of defects commonly observed Hot tearing (solidification cracking) Cold cracking (residual stresses, hydrogen embrittlement ) Blowholes, voids, gas inclusions, Corrosion or fatigue cracks Several classes of NDT : Penetrant (PT) Radiographic (RT) Electromagnetic (ET) Ultrasonic (UT) 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 3

4 CONTEXT: WELD INSPECTION BY ULTRASONIC METHODS UT drawbacks in welding structures Textured polycrystalline material: heterogeneous and anisotropic properties Beam splitting and beam deviation Anisotropic damping depending on grain geometry and grain texture US field acquisition above base metal US field acquisition above the weld bead L L T TIME T Skewing Splitting Attenuation Structural noise Difficult analysis of inspection results in welded areas CIVA modelling tools: improved diagnosis and inspection techniques by simulating numerical experiments 67th IIW Annual Assembly and International Conference 13th-18th July, 2014, Seoul, Korea Pierre CALMON 4

5 CONTEXT: WELD INSPECTION SIMULATION How to describe the weld structure? Assuming a common stiffness matrix in a local coordinate system defined by axis orientation of the grain: 3 kinds of description are proposed Piecewise description Mapping description Parametric description Large domains with respect to wavelength considering the same orientation for a set of grains Orientation of grains defined on a regular grid Grain orientation defined as a function of coordinates in the weld 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 5

6 CONTEXT: WELD INSPECTION SIMULATION Piecewise description of grain orientation Definition of large homogeneous domain with a unique crystallographic orientation Derived from post-processing of macrographic images gathering, with a tolerance threshold, the grains according to their orientation around a common average axis Advantages and drawbacks easy to implement description unrealistic artefacts and wave mode conversions due to fictive interfaces excessive approximation or difficulties to divide any welds in domains with similar orientation Piecewise description 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 6

7 CONTEXT: WELD INSPECTION SIMULATION Mapping description of grain orientation The grain orientation is given on a regular grid with a spatial sampling depending on the process to define these orientations Derived from post-processing of macrographic images extracting orientation from gradient-based operators (OrientationJ, ImageJ's plugin for directional analysis in images) simulation tools modelling the grain structure formation during solidification» MINA (Modelling anisotropy from Notebook of Arc Welding) - LCND/EDF» CAFE module - ESI Group Advantages and drawbacks accurate description requires a smoothing procedure for ray-based models Mapping description 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 7

8 CONTEXT: WELD INSPECTION SIMULATION Parametric description of grain orientation Empiric laws deduced from observation Derived from Analytical formulation of grain orientation e.g. Ogilvy s law for V-shaped weld Parametric description θ = arctan arctan T(D + z tan α) y η pour y 0; T(D + z tan α) ( y) η pour y < 0. Advantages and drawbacks easy-to-use description accounting for anisotropy effects Too simplistic characterization without any local variability Grain orientation defined as a function of coordinates in the weld 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 8

9 CONTEXT: WELD INSPECTION SIMULATION Usual modelling tools for NDT applications Finite Element Method (FEM) or Finite Difference Method (FDM) Industrial FEM codes: ABAQUS, ANSYS, COMSOL FDM academic codes: EFIT, SimSonic, ACEL-NDT, ATHENA FEM code (EDF R&D) specifically dedicated to NDT inspections in welds using fictitious domain method for defects of complex geometry Probe Weld FE calculation zone Ray-based method with paraxial approximation Dynamic Ray Tracing (model used in CIVA) Gaussian Beam Gaussian Wave Packet Defect 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 9

10 MODELLING OF WELD INSPECTION WITH THE CIVA SOFTWARE 67 th IIW Annual Assembly and International Conference Pierre CALMON 10

11 32 mm MODELLING OF WELD INSPECTION IN CIVA Beam simulation with piecewise description of weld in CIVA DRT method manages only piecewise homogeneous descriptions in the current CIVA version Propagation: in each homogeneous domain ray tracing is a straight line in a constant direction of energy Reflexion/Refraction: Snell s law is applied on the interface between 2 homogeneous domains Good agreement with other FE codes if some conditions are met: domains characteristic lengths >> wavelength small contrast of impedance between adjacent domains 12.7 mm L0 contact probe 2.25 MHz FEM Athena (EDF) Chassignole PhD Thesis λ 2,5mm 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 11

12 MODELLING OF WELD INSPECTION IN CIVA Illustration of ray model limits for a piecewise description Comparison for 2 different descriptions 3λ Side drilled hole (located at the same depth) λ Contrast of impedance equivalent in the two descriptions Weld #1 respecting the ray theory validity condition Weld #2 not respecting the ray theory validity condition Comparison of the results with hybrid Finite Element Code (CIVA/ATHENA) Finite Element Box Incident field computed with CIVA 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 12

13 MODELLING OF WELD INSPECTION IN CIVA 3λ Illustration of ray model limits for a piecewise description Side-drilled hole echo simulations for weld #1 (dimensions around 3λ) Hybrid Code Athena/CIVA DRT model in CIVA 0.2dB λ Scanning position Scanning position Good agreement between FE model and the DRT model Side-drilled hole echo simulations for weld #2 (dimensions around λ) Hybrid Code Athena/CIVA DRT model in CIVA Time - CIVA - Athena 6.3dB Scanning position Scanning position Discrepancies between FE model and the DRT model (amplitude and position) Time - CIVA - Athena 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 13

14 MODELLING OF WELD INSPECTION IN CIVA From a piecewise description of weld to a equivalent material with smoothly inhomogeneous properties Drawbacks of the piecewise description Interfaces generate unrealistic artefacts and wave mode conversions Penalizing description for the ray model: simulation variations with respect to domain geometry definitions Inapplicable or too approximate description for a lot of weld types Advantages of a equivalent smoothly inhomogeneous material Can be deduced directly from parametric description or from mapping description with smoothing filtering process Well-adapted and generic approach for a lot of weld types Modelling an average behavior of the coherent wave front used for the inspection Extension of DRT model for smoothly inhomogeneous anisotropic material in next CIVA version 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 14

15 MODELLING OF WELD INSPECTION IN CIVA DRT model in smoothly inhomogeneous anisotropic material Evaluation of ray-paths and travel time Deduced from Eikonal equation position of the ray slowness of the ray with a ijkl = ρ 1 c ijkl Energy velocity vector Polarization vector Differential equation to solve, called axial ray system, defining the ray trajectory Computation of ray amplitude Deduced from the Transport equation in a ray tube (energy conservation) assuming paraxial approximation dδx i dt = A ijδx j + B ij δp j dδp i dt = C ijδx j + D ij δp j V. Cerveny, Seismic Ray Theory, Cambridge University Press, 2001 A. Gardahaut et al., QNDE, 2013 Another differential equation to solve, called paraxial ray system, defining the evolution of the ray tube associated to the axial ray trajectory 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 15

16 MODELLING OF WELD INSPECTION IN CIVA DRT model in smoothly inhomogeneous anisotropic material Higher computation cost than for straight line ray tracing (piecewise description) Iterative time step procedures to solve differential equations Euler or RK4 schemes performed with adaptive step Examples of ray tracing in the CIVA scene L45 case T45 case 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 16

17 NUMERICAL VALIDATION: COMPARISON WITH FE CALCULATION Comparison with FE calculation (ATHENA code) First validation with a closed-form description of grain orientation the assumption of smoothly inhomogeneous media is observed Parametric description FE method Hybrid Finite Element Code DRT method Dynamic Ray Tracing J.A. Ogilvy, NDT International, Hybrid Finite Element Code -- Dynamic Ray Tracing Very good agreement between the two simulated results 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 17

18 NUMERICAL VALIDATION: COMPARISON WITH FE CALCULATION Comparison with FE calculation (ATHENA code) Validation with a mapping description of the weld assumption of smoothly inhomogeneous media assumed following a spline interpolation on the grid Mapping description Image processing macrography of the weld 2x2 mm mapping of grain orientation interpolation 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 18

19 NUMERICAL VALIDATION: COMPARISON WITH FE CALCULATION Comparison with FE calculation (ATHENA code) Validation with a mapping description of the weld Mapping description FE method DRT method Differences below 1.5 db between the two models 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 19

20 EXPERIMENTAL COMPARISONS MOSAICS Project Characteristics of the inspected welded mock-up Specific mock-up with calibrated flaws (SDH and notches) SMAW weld realized in vertical position disorientation of the fiber axis along the welding direction (about 18 ) (XZ) inspection plane is not a plane of symmetry (3D case) SDH1/SDH2 1.5 mm N1/N2/N3 10 mm height N3 located into the weld 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 20

21 EXPERIMENTAL COMPARISONS MOSAICS Project Properties used for simulation Anisotropic elastic properties obtained with characterization process (N. Alaoui Ismaili et al., QNDE, 2013) Anisotropic damping properties (2D description only) 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 21

22 EXPERIMENTAL COMPARISONS MOSAICS Project Comparison with L45 inspection at 2MHz Experimental CScan IP1 SDH1 echoes SDH2 echoes N1 echoes N2 echoes IP2 N3 echoes IP3 Analysis of comparisons in these 3 inspections planes 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 22

23 DRT model Experiment EXPERIMENTAL COMPARISONS MOSAICS Project Study of SDH echoes: SDH1 : ref. SDH2 :-11.5dB DRT model in CIVA Experimental data SDH1 : ref. SDH2 :-11 db very good agreement of direct echoes before and after passing through the welding joint 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 23

24 DRT model Experiment EXPERIMENTAL COMPARISONS MOSAICS Project Study of N1 and N2 echoes: N1 : corner LL N1 : corner LLT N1 : corner TT N2 : corner LL DRT model in CIVA Experimental data N1 : corner LL N1 : corner LLT N2 : corner LL N1 : corner TT simulated mixed corner echo (LLT) of N1 notch overestimated with respect to other corner echoes good agreement especially for the LL corner echoes 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 24

25 DRT model Experiment EXPERIMENTAL COMPARISONS MOSAICS Project Study of N3 echoes located into the weld: N3 : corner LL N3 : corner LLT DRT model in CIVA Experimental data N3 : corner LL worse result: - 4 db discrepancy for the LL echo - mixed corner echo not simulated weld seam description not enough precise with regards to UT in this area 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 25

26 CONCLUSION AND PERSPECTIVES 67 th IIW Annual Assembly and International Conference Pierre CALMON 26

27 CONCLUSIONS Evolution of modelling in CIVA to perform NDT in welds using a ray-based approximation on a smoothly inhomogeneous anisotropic medium GUI tools introduced in CIVA to manage such description (parametric or mapping descriptions) Manage 3D configurations in terms of probe, defect and material with a more realistic descriptions of welding joint Validations: Numerical validation: P-wave field successfully compared with FE code with a closed-form expression and a mapping description provided from a macrograph image processing Comparisons with experimental acquisitions: good agreement when flaws located outside the weld in the base metal discrepancies observed when the notch is located at the weld bead 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 27

28 PERSPECTIVES Weld description: facilitate the procedures for defining the properties of welds Mechanical properties and grain properties in weld Analysis automated tools of macrography Import of descriptions provided by numerical simulation of welding process Geometry of weld Set of predefined geometric description of weld 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 28

29 PERSPECTIVES Ray based modelling in CIVA: qt modes modelling in progress for inhomogeneous anisotropic medium handle with 3D anisotropy of the wave attenuation improve the computation time and the numerical precision investigate the sensitivity of the model according to the descriptions of welds obtained by macrography or simulation codes Model more accurately the interaction of the ultrasonic wave with the polycrystalline structure of welds; determine the anisotropic behavior of the attenuation and wave velocity according to the wavefront direction 67 th IIW Annual Assembly and International Conference 13 th -18 th July, 2014, Seoul, Korea Pierre CALMON 29