This paper summarizes the basics of pulsed thermal nondestructive testing (TNDT) including theoretical solutions, data processing algorithms and practical implementation. Typical defects are discussed along with 1D analytical and multi-dimensional numerical solutions. Special emphasis is focused on defect characterization by the use of inverse solutions. A list of TNDT terms is provided. Applications of active TNDT, mainly in the aerospace industry, are discussed briefly, and some trends in the further development of this technique are described.

Review of pulsed thermal NDT: Physical principles, theory and data processing

1 Introduction- 2 Ionizing Radiation Computed Tomography- 3 Thermal Imaging- 4 Microwave Imaging- 5 Ultrasonic Imaging- 6 Nuclear Magnetic Resonance- 7 Neutron Imaging- References- List of Notations- Color Plates

Nondestructive Characterization and Imaging of Wood

The complexity of materials aging may be seen as a result of the interplay between several activation processes operating on multiple spatial and temporal scales. Though the disciplines involved may seem disparate at first, material aging fundamentally could be linked by the same set of underlying activations and responses of the system. We examine how recent studies of shear-induced deformation and rheological flow initiated in the soft-matter community can be leveraged to probe the mechanisms of radiation damage in nuclear materials. Bridging these two traditionally separate areas of research demonstrates the emerging notions of mesoscale science as a research frontier concerned with linking macroscale behavior to microscale processes in driven systems. We suggest the combining of microstructuresensitive measurements with fundamental theories and mechanism-specific simulations is essential to addressing metastable materials responses of strongly activated states.

Current Opinion in Solid State and Materials Science

An overview of the application of the photothermal technique for optical as well as thermophysical characterizations of thin films is given. The peculiarities of this technique are discussed in some detail, and selected important results are pointed out. Emphasis is placed on the influence of both residual absorption and randomly distributed inhomogeneities in thin films on their laser-damage resistance.

Photothermal measurements on optical thin films

The thermographic images of laser-heated spots or lines are perturbed by nearby cracks, providing NDE techniques for crack detection Scanning with a laser line, rather than a laser spot, results in a substantial reduction in inspection time 3D finite difference modelling results are presented that show the sensitivity of the laser-line thermography technique to cracks of varying lengths, depths and openings A novel crack imaging technique is presented that is based on assembling the second spatial derivative thermal images of a scanned laser line Experimental results show the new technique to image cracks with openings as small as a few micrometres The scanning time of the laser-line thermography technique is shown to be over an order of magnitude smaller than that of the laser-spot thermography technique whilst producing crack images of similar quality

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Crack imaging by scanning laser-line thermography and laser-spot thermography

(Carslaw I959), with temperature T, coordinate z, mass density p, specific heat c, thermal conductivity k, and time t. This type of equation is known from diffusion. As the equation is not symmetrical with respect to time inversion, it describes an irreversible process which steadily reduces existing gradients. On this basis it is difficult to imagine what a thermal wave could be. A wave is characterized by a periodicity in time and space. The question is, therefore, whether a temperature periodicity in time is correlated with a periodicity along the z-coordinate. If temperature is modulated at the plane z = 0 at the angular frequency cl and with amplitude ATO, then the modulation at z > 0 is (Carslaw & Jaeger 1959)

G. Busse

Papers

Imaging with Optically Generated Thermal Waves