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Journal ArticleDOI

A comparison between finite element modeling and various thermographic non-destructive testing techniques for the quantification of the thermal integrity of macro-brush plasma facing components used in a tokamak

TL;DR: The brazing quality was quantified by establishing a comparison between the experimental results and the results from Finite Element Analysis (FEA), and the percentage of contact between the PFM and the substrate was varied in FEA.
Abstract: The plasma facing components (PFCs) inside a tokamak are typically exposed to extremely high heat flux of the order of MW/m(2). The brazing quality between the plasma facing materials (PFMs) and the heat sink will determine the structural integrity and hence the effective service life of these PFCs. Suitable non-destructive testing (NDT) techniques for the pre-qualification of these components are thus essential to evaluate their structural integrity at various stages of their service life. Macro-brush type mockups of prototype PFCs with graphite as PFM have been inspected for their brazing quality using different active Infrared (IR)-thermographic NDT techniques. The results obtained from these techniques are compared and discussed. The brazing quality was quantified by establishing a comparison between the experimental results and the results from Finite Element Analysis (FEA). The percentage of contact between the PFM and the substrate was varied in FEA. FEA results when compared with experiments shows that tiles have different amounts of contact with the substrate ranging between 10% and 80%.
References
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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

Journal ArticleDOI
TL;DR: In this article, a lock-in infrared thermography (LIT) was used to estimate the sizes and locations of subsurface defects using a fixed number of pixels, where the inspected image is shifted to obtain a shifted image while subtraction of one image from the other gives the shearing-phase distribution.
Abstract: This paper describes the quantitative determination of the sizes and locations of subsurface defects using lock-in infrared thermography. A phase (or temperature) difference between the defect area and the healthy area indicates the qualitative location and size of the defect. To accurately estimate these parameters, the shearing-phase technique has been employed, where the inspected image is shifted by a certain number of pixels to obtain a shifted image while subtraction of one image from the other gives the shearing-phase distribution. The shearing-phase distribution has maximum, minimum, and zero points that help determine quantitatively the size and location of the subsurface defect. Experimental results for a steel plate with artificial subsurface defects show good agreement with actual values.

104 citations

Journal ArticleDOI
TL;DR: In this article, the authors provide the background for this selection vis-a-vis the operating parameters expected during normal and off-normal conditions, and the reasons for the specific grades of armour materials are also described.
Abstract: The selection of the armour materials for the Plasma Facing Components (PFCs) of the International Thermonuclear Experimental Reactor (ITER) is a trade-off between multiple requirements derived from the unique features of a burning fusion plasma environment. The factors that affect the selection come primarily from the requirements of plasma performance (e.g., minimise impurity contamination in the confined plasma), engineering integrity, component lifetime (e.g., withstand thermal stresses, acceptable erosion, etc.) and safety (minimise tritium and radioactive dust inventories). The current selection in ITER is to use beryllium on the first-wall, upper baffle and on the port limiter surfaces, carbon fibre composites near the strike points of the divertor vertical target and tungsten elsewhere in the divertor and lower baffle modules. This paper provides the background for this selection vis-a-vis the operating parameters expected during normal and off-normal conditions. The reasons for the selection of the specific grades of armour materials are also described. The effects of the neutron irradiation on the properties of Be, W and carbon fibre composites at the expected ITER conditions are briefly reviewed. Critical issues are discussed together with the necessary future R&D.

66 citations

Journal ArticleDOI
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

Journal ArticleDOI
01 Nov 2005
TL;DR: This new facility SATIR UPGRADE has been designed for the full non-destructive examination of the high heat flux (HHF) components taking into account main improvements of the SATIR facility.
Abstract: Among all non-destructive examinations (NDE), active infrared thermography is becoming recognised as a technique available today for improving quality control of many materials and structures involved in heat transfer. The infrared thermography allows to characterise the joint between two materials. In order to increase the defect detection limit of the SATIR test bed, several possibilities have been evaluated. The implementation in 2003 of a microbolometer camera and the improving of the thermosignal process allowed to increase considerably the detection sensitivity of the SATIR facility. The quality, the spatial stability of infrared image and the detection of edge defect have been also improved. The coupling on the same test bed of SATIR method with a lock-in thermography will be assessed in this paper. An improvement of the global reliability is expected by data merging produced by the two thermal excitation sources. This new facility SATIR UPGRADE has been designed for the full non-destructive examination of the high heat flux (HHF) components taking into account these main improvements. These systematic acceptance tests obviously need tools for quality control of critical parts.

31 citations