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Conférence sur la thermographie infrarouge quantitative (QIRT)

15 mars 2022


Calendrier Du 4 au 8 juillet 2022
Lieu 30 rue Cabanis, 75014 Paris, Station de métro Glacière (ligne 6), Gare RER B Denfert Rochereau, Ligne directe vers l’aéroport Roissy-Charles de Gaulle, Arrêt Orly-Bus
Planning Voir le programme
Inscription Inscriptions clôturées
Stand Stand THERMOCONCEPT à retrouver sur place

Venez retrouver notre expert en Contrôle Non Destructif, Richard HUILLERY en compagnie de la société Edevis (fournisseur de matériel de pointe en contrôle non destructif), à l’occasion de cette nouvelle édition du QIRT. Ce sera l’occasion de vous faire découvrir nos différents moyens de Contrôle Non Destructif par thermographie active. Notre expert sera présent sur un stand afin de vous accueillir et d’échanger avec vous sur vos besoins.

Pour son 30ème anniversaire, le QIRT 2022 est l’occasion privilégiée de rencontrer les acteurs majeurs du domaine de la thermographie infrarouge. Lors de la conférence, les valeurs de température par thermographie infrarouge sur des matériaux et structures seront testées et le transfert de chaleur sera observé et exploité. Plusieurs thèmes seront abordés et les titres des meilleurs articles seront récompensés.

Ci-dessous une liste des résumés des articles qui seront présentés lors de la conférence et qui utilisent nos solutions de Contrôle Non Destructif : 

Laser-thermographic crack detection on an industrial scale
by P. Menner*, A. Dillenz*, A. Elrikh** and M. Taglione**

* edevis GmbH, Handwerkstr. 55, 70565 Stuttgart, Germany,

**Framatome/Intercontrôle, 4 rue Thomas Dumorey, 71 100 Chalon-sur-Saône, France,
Flying spot thermography can be used for crack detection in metallic, ceramic and polymer components. However, many systems and applications are still limited to lab scale. The Athena system from Intercontrole/Framatome uses a rotatable laser line which is scanned collinearly with the IR camera field of view over the component surface in multiple direction to reduce the influence of emissivity. This setup now has been industrialized with state-of-the-art components and optics design to raise both the performance and the technology readiness level. This paper presents the increased performance of the LTcam system on reference samples and some applications.


Active Thermography for panel paintings inspection: A comparative study of mid-wave and long-wave Infrared spectra.
by S. Boubanga Tombet*, E. Guyot*, R. Huillery**, T. Calligaro***, V. Detalle***, X.Bai***, and A. Semerok****

* Telops, avenue St.-Jean-Baptiste, Québec (Québec) Canada G2E 6J5,
** Thermoconcept, 25 rue marcel Issartier, Bat Aero Business center, Bureau 11 – 12, RDC, 33700, Merignac, France
*** C2RMF, Palais du Louvre – Porte des Lions, 14, Quai François Mitterrand, 75001, Paris, France.
**** Université Paris-Saclay, CEA, Service d’Études Analytiques et de Réactivité des Surfaces, 91191, Gif-sur-Yvette, France.
Active thermography was used for characterisation of multi-layered paintings panel structures and analysis of defects caused by aging and environmental effects. Pulsed Thermography, PTvis setup (EDEVIS GmbH, provided by Thermoconcept) was applied to provide and inspect a dynamic thermal response, which was recorded by mid- and long wavelength infrared TELOPS cameras. Control, synchronization and data analyses were provided by EDEVIS DisplayImg Professional software provided by Thermoconcept. Active thermography was demonstrated as being appropriate for characterization of various defects on painting layers and detection of under−drawings, pentimenti and canvas. Such multispectral approach provided simultaneous complementary information on the specimen under inspection.


Search for surface defects on metallic aeronautical parts by thermography with laser line.
by Stéphane AMIEL *, Loïc CLAUZADE **, Benoît GERARDIN *, Abdelhamid ZOUKAGHE *, Frédéric

* DST/NDIS/ I2T, Saf ran Tech; Chateaufort, France,,
** DI, Saf ran Aircraf t Engines; Gennevilliers France,
During the manufacturing of metal turbine discs, f luorescent penetrant inspection is performed to detect surface defects. Because it does not use chemicals and allow s the digitization of information, the inf rared thermography is envisaged as an alternative method. The exploitation of the thermal response of the material to a laser excitation, measured with an inf rared camera, allow s the imaging of possible defects.
The shape of the discs is adapted to the rotation of the part heated by a f ixed laser line in the f ield of the thermal camera. The w ork described here is carried out for the industrialization of the process.


Simulation of Induction Heating for Infrared Thermography with consideration of spectrum artefact
by Olivier GHIBAUDO*

* DSTD Digital Science and Technology Department, Safran Tech, Chateaufort, France
Induction thermography is identified as a promising non-destructive testing method for detecting and characterizing surface cracks in metals. The sample to be inspected is heated with a short induced electrical current pulse and the infrared camera records the temperature distribution and transient temporal behavior at the surface during and after the heating pulse. When a surface defect such as a crack or porosity is present, it locally modifies the electrical and thermal conductivity, so that the eddy currents are deflected and thermal gradients appear in the vicinity of the defect, allowing their detection with the help of appropriate signal and/or image processing.
For the study of metals generally inspected in aeronautics (Nickel Base superalloy, Titanium, Aluminium,…), the detection contrast associated with a defect depends on many parameters specific to induction excitation: i) the power density deposited locally and therefore the type of inductors, ii) the electromagnetic skin thickness monitored through the magnetic excitation frequency, iii) the heating time and iv) the waveform of the excitation signal. Therefore, the whole excitation chain, the inductors and inductor/workpiece coupling, the heating head including the power transformer and the oscillating RLC circuit, the power and signal generator, must be optimized in order to maximize the probability of detection of sub-millimetre defects in metallic materials. The work in [1], carried out in lock-in multi-pulse acquisition mode, highlights the importance of generating short heating periods in order to have thermal diffusion lengths less than 1mm and thus short analysis times for the inspection of small defects. In this case, the issue is to ensure a sufficient signal-to-noise ratio (SNR), and therefore to inject sufficient energy into the material by Joule effect. A solution proposed in [1] consists in repeating the induction shots N times, using the lock-in multi-pulse acquisition technique and, so, increases the SNR, in particular on the phase images of the Fourier transform.
In this paper, we propose simulations by solving the finite difference heat equation on a simple case, i.e. a plate containing a notch defect. The time signals at each pixel around the defect are simulated, in order to study the contrast between a sound area and one containing a defect. The analysis of the time derivatives of the signal and a discrete Fourier series decomposition allow to locate on the signal the most favourable portions to maximize the contrast of detection on defect. The results show that due to the low-pass behavior associated with a defect (resistance and thermal capacity), the edges of the excitation step should ideally be very fast to maximize the phase contrast associated with the defect, especially from the first moment of the induction heating. However, in real practice, the speed of these rising and falling edges is limited by artefacts: i) switching losses in the power electronics, ii) Joule and iron losses in the inductor and the heating head, iii) the imperfect impedance matching between the generator and the inductor, iv) the electrical impedance of the whole excitation chain, which introduces a speed limitation on the excitation slew rate. The originality of the proposed work consists in proposing a model able to simulate this slew rate artefact on the excitation step and to account for the thermal consequences on the degradation of the defect detection contrast. A frequency-domain representation is proposed in order to identify on the Bode diagram the thermal transfer function associated with the material response from the a priori knowledge of the emission spectrum of the excitation signal containing the slew rate artefact. This representation, using the thermal impedances, reveals a cut-off frequency associated with the healthy material, different from the cut-off frequency associated with the defect, which depends on the geometrical extent of the defect. The simulation results are compared with the experimental ones and show a good ability of the model to reproduce the artefact of the rise velocity limit of the step. Finally, the simulations allow the design of an optimal excitation chain in order to maximize the defect detection contrast.


Qualification of active thermographic methods for testing welded joints
by C. Srajbr*, E. Prints** and M. Mund***

* * edevis GmbH, Handwerkstr. 55, 70565 Stuttgart, Germany,
** Department for Cutting and Joining Manufacturing Processes,
University of Kassel, *** Institute of Joining and Welding, Technische Universität Braunschweig, Germany,
Over the past years, significant progress has been made in the application development of active thermography for the inspection of welded joints of semi-finished metal products. Various research projects have demonstrated the potential for detecting the quality-relevant flaws in these joints. With the simultaneous steady improvement of the system technology of active thermography, it has also been possible to increasingly implement pilot solutions in industrial applications. The next logical step is to incorporate the testing technique into the relevant standards for the non-destructive evaluation of welded joints so that the technology can be applied more widely and also in less automated applications. However, the integration of active thermography into the testing standards for the non-destructive evaluation requires detailed knowledge of detection possibilities as well as detection boundaries. Therefore, this paper presents the results of a study that focus on the qualification of the three most matching thermographic methods, as an alternative evaluation technique for welds. It is known that active thermographic methods differ in the excitation source. Here are chosen the most promising for the testing of metal components. The focus in this study is mainly on the application of induction-excited thermography, however, ultrasonic excitation as well as laser-based excitation are considered as well. The approach for the qualification of active thermographic methods for testing welded joints is presented and may be adopted as a standardized method for the qualification of NDT-methods in general.
To qualify the thermographic methods, a three-step approach based on artificial as well as realistic defects was chosen.
The first part of the study deals with the manufacturing of representative specimens to determine the possibilities of different thermographic methods. This should be done by selecting the materials used (steel and aluminium) and the thicknesses of the semi-finished products as close as possible to reality and relevant to the standards to achieve a high relevance and good comparability to other NDT procedures standardised for welded joints.
There are some challenges that must be meet during the specimen preparation to achieve representative and reproducible specimens with realistic defects. Based on an evaluation of typical welding defects, two groups of defects (cracks and voids) were identified as the defects most likely to be detected by thermographic measurements. Specimens containing those defects were manufactured using different approaches. First of all, specimens with defects were manufactured using variations of fusion welding (MAG). The welding processes were manipulated to obtain defects that variated in size and location. The manufactured defects covered a wide range of sizes and it could be shown, that it is possible to manufacture specimen with realistic defects. This specimens were used to demonstrate the capability of the thermographic techniques to detect typical welding defects. However, these methods lack in controllability and reproducibility, which is especially critical for inner defects. Therefore, alternative approaches based on laser powder bed fusion (LPBF) and friction stir welding were applied to manufacture specimens to achieve a higher degree of controllability and reproducibility for those defects. It can be shown, that artificial defects resembling real defects in size and location can be manufactured. These defects were the used to examine the detection limits for inner defects.
The second part deals with the thermographic testing of the specimens. The specimens were examined using three different thermographic techniques. For the comparability and repeatability of the test results, a special test stand was designed in which precise positioning of the welding specimens is possible. The test stand can be equipped with different IR cameras and excitation sources to enable comparisons to be made. In addition, the IR recordings can be easily and reliably calibrated metrically with the help of a specially developed method and associated calibration bodies. Thus, the test results can also be compared well with those of other NDT methods.
The detectability of artificial as well as realistic defects by those techniques is displayed and challenges as well as limitations are addressed. The results show the high potential of all considered thermographic techniques to detect surface breaking, two dimensional defects as cracks as well as incomplete penetrations. In contrast, it can be shown, that the detectability of relevant inner defects is limited to surface near defects. Based on the results, the detection limits and limitations for the different testing techniques are derived and requirements for the implementation of thermographic testing of welds are discussed. Based on the results, the requirements on a testing system can be derived and recommendation concerning the testing procedure can be made.
Finally, the different thermographic testing methods are assessed regarding their potential as a suitable testing method for the evaluation of welded joints by comparing the results of the thermographic tests to the requirements defined in the testing standards as well as the results of the established testing techniques. Based on this it can be recommended, to introduce thermographic testing for the testing of welds. It can be shown, that the thermographic testing methods are well suited to detect surface breaking defects and therefore, should be included in the standards for the evaluation of welds. An exemplary result of the qualification is shown in Figure 1. In case of inner defects, the suitability of thermographic
methods is limited as all the testing methods can detect all relevant welding defects due to the high requirements regarding the size of the defects to be detected specified in the existing testing standards for the evaluation of welds.


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