Tone burst eddy‐current thermography (tbet)
10 Mar 2008-Vol. 975, Iss: 1, pp 544-551
TL;DR: In this paper, a Tone Burst Eddycurrent Thermography (TBET) technique was used to generate local heating inside the material, induced by pulsed/short-time induction heating.
Abstract: This paper reports on a Tone Burst Eddycurrent Thermography (TBET) technique that uses short‐time bursts of eddy‐currents induced in conducting media to generate local heating inside the material. The transient diffusion of the heat inside the material, induced by pulsed/short‐time induction heating, is imaged by measuring the transient temperature profiles on the surface of the material. The presence and characteristics of the defects inside the materials changes the surface temperature transients and thus can be used for the nondestructive evaluation (NDE) of conducting materials. Axisymmetric numerical models of the conventional transient thermography technique are used to benchmark the TBET technique. From the temperature profile data, temperature contrast information is obtained for the different defect depths. Temperature contrast data obtained for TBET, in this process, was compared with that obtained from conventional transient thermography data. It was found that the frequency of the eddy‐current...
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TL;DR: In this article, a study on the optimum frequency of eddy current excitation that will give a maximum temperature rise for a given thickness has been conducted using both modeling and experimental techniques, and the dependency of this optimum frequency (peak frequency) on thickness, electrical conductivity, and thermal response of the sample are studied.
Abstract: The eddy current Thermography is an evolving non-contact, non-destructive evaluation method with applications especially in aircraft industries. It involves two approaches (a) the volumetric heating (skin depth much greater than the thickness) of the specimen and the observation of additional heating at defect locations due to Joule heating (called eddy-therm) and (b) the use of high-frequency eddy current bursts (skin depth is smaller than the thickness) for the transient surface/near surface heating of the objects and sensing the propagation of a “thermal wave” using a high-sensitivity infrared (IR) camera (tone burst eddy-current thermography (TBET)). In this paper, a study on the optimum frequency of eddy current excitation that will give a maximum temperature rise for a given thickness has been conducted using both modeling and experimental techniques. COMSOL 3.2 was used to solve the coupled equations of electromagnetic induction and heat transfer. The dependency of this optimum frequency (peak frequency) on thickness, electrical conductivity, and thermal response of the sample are studied. The relation between defect size and the coil inner radius is considered. The thermal responses of defective samples obtained by simulation are compared with experimental results.
36 citations
TL;DR: In this paper, an inversion method is proposed to determine simultaneously the electrical and the thermal properties of a given isotropic material from the time-temperature data obtained from tone-burst eddy current thermography (TBET).
Abstract: In this paper, an inversion method is proposed to determine simultaneously the electrical and the thermal properties of a given isotropic material from the time-temperature data obtained from tone-burst eddy current thermography (TBET). A multiphysics forward model for computing the surface temperature data was used in a genetic algorithm (GA) based inversion technique to determine the material properties such as electrical conductivity (σ), thermal conductivity (k), density (ρ), and specific heat (Cp) simultaneously. Different trials were carried out initially with simulated temperature data (with and without noise) and then validated with experiments.
27 citations
Cites background or methods from "Tone burst eddy‐current thermograph..."
...A schematic diagram of the experimental setup [6], [7] is shown in Fig....
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...In the present work, an attempt has been made to simultaneously determine the electrical and the thermal properties of a given sample using inversion technique from the observed temperature data in tone-burst eddy current thermography [6]–[15]....
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...Both the coil and the specimen were placed in air domain [6], [7]....
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TL;DR: Several recent advances that have significantly extended imaging methods from laboratory development into practical applications were summarized, followed by conclusions and discussion on future directions.
Abstract: In this article, the state-of-the-art multi-wave and hybrid imaging techniques in the field of nondestructive evaluation and structural health monitoring were comprehensively reviewed. A new direction for assessment and health monitoring of various structures by capitalizing the advantages of those imaging methods was discussed. Although sharing similar system configurations, the imaging physics and principles of multi-wave phenomena and hybrid imaging methods are inherently different. After a brief introduction of nondestructive evaluation (NDE) , structure health monitoring (SHM) and their related challenges, several recent advances that have significantly extended imaging methods from laboratory development into practical applications were summarized, followed by conclusions and discussion on future directions.
21 citations
Cites background from "Tone burst eddy‐current thermograph..."
...This technique, also known as eddy current thermography [8–11], tone burst eddy current thermography (TBET) [12–14], thermo-inductive inspection and induction thermography [15–17], combines electromagnetic illumination of the work-piece, heating up of the material by induction and imaging by transient infrared thermography to provide a fast and efficient method for defect detection and material characterization over a relatively large area....
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..., they discussed the applications of TBET and compared it with conventional thermography techniques [12]....
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...The inversion of the TBET data was executed with the use of the genetic algorithm (GA)-based inversion method, which can be summarized as shown in Figure 3....
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...The typical apparatus of TBET is illustrated in Figure 2....
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...In the paper published by Kumar et al., they discussed the applications of TBET and compared it with conventional thermography techniques [12]....
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TL;DR: The Inner Fixed Structure (IFS) bond panel is a honeycomb sandwich panel with CFRP facesheet and a heat shield on one side, and a perforated CFRP faceheet on the other side, of a jet engine nacell as mentioned in this paper.
Abstract: The Inner Fixed Structure (IFS) bond panel is a honeycomb sandwich panel with CFRP facesheet and a heat shield on one side, and a perforated CFRP facesheet on the other side, of a jet engine nacell...
11 citations
Cites background from "Tone burst eddy‐current thermograph..."
...Induction thermography [11] relies on heat generated within the material due to eddy currents....
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21 Oct 2016
TL;DR: In this paper, the authors presented the possibility of applying eddy current thermography method for detecting defects in ballistic covers made of carbon fiber reinforced composites used in the construction of military vehicles.
Abstract: Eddy current thermography is a new NDT-technique for the detection of cracks in electro conductive materials. It combines the well-established inspection techniques of eddy current testing and thermography. The technique uses induced eddy currents to heat the sample being tested and defect detection is based on the changes of induced eddy currents flows revealed by thermal visualization captured by an infrared camera. The advantage of this method is to use the high performance of eddy current testing that eliminates the known problem of the edge effect. Especially for components of complex geometry this is an important factor which may overcome the increased expense for inspection set-up. The paper presents the possibility of applying eddy current thermography method for detecting defects in ballistic covers made of carbon fiber reinforced composites used in the construction of military vehicles.
9 citations
Cites background from "Tone burst eddy‐current thermograph..."
...The density of absorbed heat radiation power is lower than the one provided during heating by sources of optical radiation; however, induction heating does not cause disturbances by reflected radiation [6-8]....
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References
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TL;DR: In this paper, a high-intensity short-duration light pulse is absorbed in the front surface of a thermally insulated specimen, and the resulting temperature history of the rear surface is measured by a thermocouple and recorded with an oscilloscope and camera.
Abstract: A flash method of measuring the thermal diffusivity, heat capacity, and thermal conductivity is described for the first time. A high‐intensity short‐duration light pulse is absorbed in the front surface of a thermally insulated specimen a few millimeters thick coated with camphor black, and the resulting temperature history of the rear surface is measured by a thermocouple and recorded with an oscilloscope and camera. The thermal diffusivity is determined by the shape of the temperature versus time curve at the rear surface, the heat capacity by the maximum temperature indicated by the thermocouple, and the thermal conductivity by the product of the heat capacity, thermal diffusivity, and the density. These three thermal properties are determined for copper, silver, iron, nickel, aluminum, tin, zinc, and some alloys at 22°C and 135°C and compared with previously reported values.
3,471 citations
Book•
30 Apr 2001
TL;DR: In this paper, the authors present an active and passive approach to active thermography for nondestructive testing of infrared sensors and Optic Fundamentals using Matlab M-Scripts.
Abstract: Preface. Getting Started with Thermography for Nondestructive Testing. FUNDAMENTAL CONCEPTS. Introduction to Thermal Emission. Introduction to Heat Transfer. Infrared Sensors and Optic Fundamentals. Images. Automated Image Analysis. Materials. Experimental Concepts. ACTIVE THERMOGRAPHY. Active Thermography. Quantitative Data Analysis in Active Thermography. ACTIVE AND PASSIVE THERMOGRAPHY: CASE STUDIES. Applications. References and Bibliography. Appendix A: Computer Model. Appendix B: Smoothing Routing. Appendix C: Parabola Computations. Appendix D: Higher-Order Gradient Computations Based on the Roberts Gradient. Appendix E: Properties of Metals and Nonmetals. Appendix F: Matlab M-Scripts Available. Index.
1,556 citations
"Tone burst eddy‐current thermograph..." refers methods in this paper
...Recorded images over several time frames are processed for extracting the internal flaw information [ 6-10 ]....
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TL;DR: In this paper, the authors proposed a deterministic active thermographic response is deterministic, to the extent that the postexcitation time evolution for a defect-free sample can be accurately predicted using a simple one-dimensional model.
Abstract: Active thermography has gained broad acceptance as a non- destructive evaluation method for numerous in-service and manufactur- ing applications in the aerospace industry. However, because of the dif- fusive nature of the process, it is subject to blurring and degradation of the signal as one attempts to image deeper subsurface features. Despite this constraint, active thermographic response is deterministic, to the extent that the postexcitation time evolution for a defect-free sample can be accurately predicted using a simple one-dimensional model. In the patented thermal signal reconstruction method, the time history of every pixel in the field of view is compared to such a model in the logarithmic domain, where deviations from ideal behavior are readily identifiable. The process separates temporal and spatial nonuniformity noise compo- nents in the image sequence and significantly reduces temporal noise. Time-derivative images derived from the reconstructed data allow detec- tion of subsurface defects at earlier times in the sequence than conven- tional contrast images, significantly reducing undesirable blurring effects and facilitating detection of low-thermal-contrast features that may not be detectable in the original data sequence. © 2003 Society of Photo-Optical In-
413 citations
"Tone burst eddy‐current thermograph..." refers methods in this paper
...Recorded images over several time frames are processed for extracting the internal flaw information [ 6-10 ]....
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Book•
30 Jun 1990
TL;DR: In this paper, a theoretical and practical treatment of both conduction and induction heating, comprising four parts: conduction theory, induction theory, heat flow, and practice, is presented.
Abstract: Offers a theoretical and practical treatment of both conduction and induction heating, comprising four parts: conduction theory, induction theory, heat flow, and practice.
167 citations
Patent•
30 Oct 1997
TL;DR: In this paper, a non-destructive testing technique and system for locating flaws within an object is proposed. But the method is limited to transient depth thermography (TDPT).
Abstract: The present invention relates to transient depth thermography; a nondestructive testing technique and system for locating flaws within an object. The system, which comprises a heater for heating the surface of the object; a recorder for recording pixel intensity for each pixel on the heated surface; a means for determining pixel contrast from the pixel intensity; and a means for determining the size and location of flaws within the object based upon the pixel contrast; monitors each pixels' contrast for successive thermal images and utilizes those pixel contrasts determining the location of a flaw within the object. The object surface and the respective underlying flaws can then be depicted on a color spectrum image print which correlates the flaw depth with a particular color.
89 citations