Characterization of vertical buried defects using lock-in vibrothermography: I. Direct problem

Mendioroz, A.; Castelo, A.; Celorrio, R.; Salazar, A.

doi:10.1088/0957-0233/24/6/065601

Cited by 29 publications

(26 citation statements)

References 25 publications

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“…In order to prevent the sample from being damaged [11,12] and to reduce the time needed for the sample to reach equilibrium [8], experiments have been carried out with a low excitation power (below 40 W) instead of the usual powers, above 250 W [8]. The price to be paid is a dramatic reduction of the amplitude of the oscillating component.…”

Section: Methodsmentioning

confidence: 99%

“…The sample is thick enough to be considered as semi-infinite. Assuming adiabatic boundary conditions and homogeneous heat sources, the surface temperature distribution can be represented in a complex form as [8] T (x, y, 0) =…”

Section: Direct Problemmentioning

confidence: 99%

“…In our approach, we assume heat is generated at the defects and study the surface temperature distribution it produces in lock-in vibrothermography experiments. In previous works, we modeled the surface temperature distribution corresponding to vertical buried heat sources (defects) [8] and developed an inversion algorithm to retrieve the shape and location of the heat source [9]. In this work, we analyze the capability of the method to retrieve vertical square heat sources at increasing depths by performing inversions with synthetic data with added white noise.…”

Section: Introductionmentioning

confidence: 99%

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Defect Characterization from Lock-in Vibrothermography Data

et al. 2014

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A method to characterize vertical cracks which combines lock-in vibrothermography experiments and a stabilized inversion algorithm is presented. The capability of the method to retrieve the shape and location of square cracks buried at increasing depths is analyzed by inverting synthetic data with added white noise. Moreover, the ability of the method to resolve two square buried cracks as a function of depth is studied. A relationship between the depth of the cracks and the minimum distance between them in order to obtain separate reconstructions is found. The predictions of the inversions with synthetic data have been checked by inverting experimental data obtained from steel samples containing calibrated cracks. In order to prevent the sample from being damaged and to reach the steady state faster, low ultrasound excitation powers are used. The signal-to-noise ratio corresponding to the resulting weak signal is improved by processing a large number of infrared images using the lock-in method. The experimental results confirm that the method is able to reconstruct square heat sources whose depth is twice their lateral dimension, and that the resolution condition holds.

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Section: Methodsmentioning

confidence: 99%

Section: Direct Problemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Defect Characterization from Lock-in Vibrothermography Data

et al. 2014

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“…Among the different methods used to tackle heat source reconstruction, the work of Castelo et al [3][4][5][6][7][8] proposes detecting defects present in a vertical plane on the surface of the material by exciting them with modulated (lock-in) or pulsed (burst) acoustic waves, creating a thermal source at the spot of the defect; the characterization of the defect takes place by the characterization of the resulting thermal source. This reconstruction uses an original regularization term.…”

Section: Introductionmentioning

confidence: 99%

Bayesian Inference for 3D Volumetric Heat Sources Reconstruction from Surfacic IR Imaging

et al. 2020

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The domain of non-destructive testing (NDT) or thermal characterization is currently often done by using contactless methods based on the use of an IR camera to monitor the transient temperature response of a system or sample warmed by using any heat source. Though many techniques use optical excitation (flash lamps, lasers, etc.), some techniques use volumetric sources such as acoustic or induction waves. In this paper, we propose a new inverse processing method, which allows for the estimation of 3D fields of heat sources from surface temperature measurements. This method should be associated with volumetric heat source generation. To validate the method, a volumetric source was generated by the Joule effect in a homogeneous PVC sample using an electrical thin cylindrical wire molded in the material. The inverse processing allows us to retrieve the depth of the wire and its geometrical shape and size. This tool could be a new procedure for retrieving 3D defects on NDT.

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“…Then, the study has been extended on 3D problems; several pioneering teams have proposed methods based on thermal and acoustic coupling [2][3][4][5][6] or by introducing the concept of virtual waves [7,8]. These methods of reconstruction that exist today enable reconstructing volume data (sources, initial conditions, etc.)…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Reconstruction of Thermal Volumetric Sources from Surface Temperature Fields Measured by Infrared Thermography

et al. 2019

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Non-destructive testing (NDT) of materials and structures is a very important industrial issue in the fields of transport, aeronautics and space as well as in the medical domain. Active infrared thermography is an NDT method that consists of providing an external excitation to cause an elevation of the temperature field in the material, consequently allowing evaluation of the resulting temperature field at the surface. However, thermal exciters that are used (flash lamps, halogen, lasers) act only on the surface of the sample. On the other hand, several energy conversion systems can lead to the generation of volumetric sources; the phenomena of thermo-acoustics, thermo-induction, thermomechanics or thermochemistry can be cited. For instance, ultrasonic waves can generate volumetric heat sources if the material is viscoelastic or if there is a defect. The reconstruction of these sources is the initial process for the quantification of parameters responsible for the heating. Characterizing a heat source means reconstructing its geometry and the supplied power. Identification of volumetric heat sources from surface temperature fields is a mathematically ill-posed problem. The main cause of the issue is the diffusive nature of the temperature. In this work, 3D reconstruction of the volumetric heat sources from the resulting surface temperature field, measured by infrared thermography, is studied. An analysis of the physical problem enables specifying the limits of the reconstruction. In particular, a criterion on the achievable spatial resolution is defined, and a reconstruction limitation for in-depth sources is highlighted.

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Characterization of vertical buried defects using lock-in vibrothermography: I. Direct problem

Cited by 29 publications

References 25 publications

Defect Characterization from Lock-in Vibrothermography Data

Defect Characterization from Lock-in Vibrothermography Data

Bayesian Inference for 3D Volumetric Heat Sources Reconstruction from Surfacic IR Imaging

Three-Dimensional Reconstruction of Thermal Volumetric Sources from Surface Temperature Fields Measured by Infrared Thermography

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