Resolution of photothermal tomographic imaging of subsurface defects in metals with ray optic reconstruction

Munidasa, Mahendra; Mandelis, Andreas; Ferguson, Charmaine S.

doi:10.1007/bf00323844

Cited by 23 publications

(10 citation statements)

References 18 publications

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“…In a later version, both the sample and the tip were placed on separate micrometer stages with steppingmotors so that both the laser and the pin position could be scanned over a 4 mm horizontal range [205,206]. The apparatus is shown in Figure 33.…”

Section: -I I-isoladonmentioning

confidence: 99%

Pyroelectric polymer electrets

Bauer

Lang

1996

IEEE Trans. Dielect. Electr. Insul.

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Pyroelectricity is the electrical response of a material to a change in temperature. It exists in polymers which contain spontaneous or frozen polarization resulting from oriented dipoles. This review describes the physical basis for the existence of the pyroelectric effect and discusses its behavior in a number of amorphous, semicrystalline, crystalline and liquid crystalline polymers. Some of the techniques for measurement of the pyroelectric effect are presented and its use in pyroelectric relaxation spectroscopy and thermal analysis is described. The spatial distribution of polarization and space charge through the thickness of polymer films can be determined by several thermal pyroelectric techniques. Recent developments in the integration of pyroelectric polymer infrared detectors with solid-state silicon devices are described. One of the most important recent applications of polymers is in photopyroelectric spectroscopy which can be used for the determination of a number of thermal and optical properties of materials. Finally, some miscellaneous applications in physics, chemistry and biology are presented.Polar liquid crystals (LC) seem to,be very interesting materials for pyroelectric applications, due to the strong orientation of

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Section: -I I-isoladonmentioning

confidence: 99%

Pyroelectric polymer electrets

Bauer

Lang

1996

IEEE Trans. Dielect. Electr. Insul.

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“…The most challenging is the evaluation of h and d (or Rd). Many algorithms for characterizing h and Rd have been proposed elsewhere [2][3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

1D and 3D defect characterization in IR thermographic NDT

Vavilov¹,

Chulkov²

2019

Proceedings of QIRT Asia 2019

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Defect characterization is a specific procedure of IR thermographic nondestructive testing (NDT) which follows a stage of defect detection. Both procedures can be reference-free or introduce a reference area defined automatically or by the thermographer. The typical reference-free concepts are Pulse Phase Thermography (PPT), Principal Component Analysis (PCA), Thermographic Signal Reconstruction (TSR) and some others. However, by choosing a reference point close to a suspicious (allegedly defect-linked) zone one may consider subtle differences between defect and non-defect areas. Such differences are typically related to differential temperature signals which, in their turn, can be converted into phase shift signals, effusivity variations, etc. In this study, two approaches, namely, analytical formulas and a neural network, have been applied to characterize defects in composites.

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“…The DTT concept above has been called phenomenological because it utilizes observable phenomena of heat diffusion in solids and involves no "precise" solutions to inverse heat conduction problems. There are a plenty of more accurate approaches to thermal tomography but their consideration is beyond the scope of this study (see [3][4][5][6][7][8][9][10][11][12][13][14][15]).…”

Section: Introductionmentioning

confidence: 99%

Time- and Phase-Domain Thermal Tomography of Composites

2018

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Active infrared (IR) thermographic nondestructive testing (NDT) has become a valuable inspection method for composite materials due to its high sensitivity to particular types of defect and high inspection rate. The computer-implemented thermal tomography, based on the analysis of heat diffusion in solids, involves a specialized treatment of the data obtained by means of active IR thermographic NDT, thus allowing for the “slicing” of materials under testing for a few layers where discontinuity-like defects can be underlined on the noise-free background (binary thermal tomograms). The time-domain thermal tomography is based on the fact that, in a one-sided test, temperature “footprints” of deeper defects appear later in regard to shallower defects. The phase-domain tomography can be applied to collected IR data in a direct way, for instance, by using the Fourier transform, but quantification of results is more difficult because the relationships between phase and defect depth depend on experimental parameters, and the corresponding “phase vs. defect depth” calibration functions are ambiguous. In this study, the time- and phase-domain thermal tomography techniques have been compared on simulated IR thermograms and experimentally applied to the evaluation of carbon fiber reinforced plastic composite containing impact damage defects characterized by impact energy 10, 18, and 63 J. Both tomographic techniques have demonstrated similar results in the reconstruction of thermal tomograms and, in some cases, supplied complementary information about the distribution of single defect zones within impacted areas.

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Resolution of photothermal tomographic imaging of subsurface defects in metals with ray optic reconstruction

Cited by 23 publications

References 18 publications

Pyroelectric polymer electrets

Pyroelectric polymer electrets

1D and 3D defect characterization in IR thermographic NDT

Time- and Phase-Domain Thermal Tomography of Composites

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