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The increasing deterioration of panel paintings can be due to physical processes that take place during exhibition or transit, or as a result of temperature and humidity fluctuations within a building, church or museum. In response to environmental alterations, a panel painting can expand or contract and a new equilibrium state is eventually reached. These adjustments though, are usually accompanied by a change in shape in order to accommodate to the new conditions. In this work, a holographic method for detecting detached regions and micro-cracks is described. Some of these defects are confirmed by Thermographic Signal Reconstruction (TSR) technique. In addition, Pulsed Phase Thermography (PPT) and Principal Component Thermography (PCT) allow to identify with greater contrast two artificial defects in Mylar which are crucial to understand the topic of interest: the discrimination between defect materials. Finally, traditional contact ultrasounds applications, are widely applied for the evaluation of the wood quality in several characterization procedures. Inspecting the specimen from the front side, the natural and artificial defects of the specimen are confirmed. Experimental results derived by the application of the integrated methods on an Italian panel painting reproduction, called The Angel specimen, are presented. The main advantages that these techniques can offer to the conservation and restoration of artworks are emphasized.

In thermography surveys, the inspector uses the camera to acquire images from the examined part. Common problems are the lack of repeatability when trying to repeat the scanning process, the need to carry the equipment during scanning, and long setting-up time. The aim of this paper is to present transient thermography results on CFRP plates for assessing different types of fabricated defects (impact damage, inclusions for delaminations, etc), as well as and to discuss and present a prototype robotic scanner to apply non destructive testing (thermographic scanning) on materials and structures. Currently, the scanning process is not automatic. The equipment to be developed, will be able to perform thermal NDT scanning on structures, create the appropriate scanning conditions (material thermal excitation), and ensure precision and tracking of scanning process. A thermographic camera that will be used for the image acquisition of the non destructive inspection, will be installed on a x, y, z, linear manipulator's end effector and would be surrounded by excitation sources (optical lamps), required for the application of transient thermography. In this work various CFRP samples of different shape, thickness and geometry were investigated using two different thermographic systems in order to compare and evaluate their effectiveness concerning the internal defect detectability under different testing conditions.

Infrared thermography could be an important diagnostic tool for assessing the performance of photovoltaic panels. Malfunctions, material and insulation defects can be detected easily and fast without complicated proceedings. It can be applied to large and small scale systems so as to secure the best possible function and thus performance of the panel(s). In this work, a thermographic survey was performed on a photovoltaic plant of 1 MW in Greece. Various deficiencies were detected by using in situ thermography. Although these panels were only a few months into use, there were defected areas spotted by thermography, indicating the poor performance of these panels and thus affecting the total power output of the photovoltaic plant.

Pulsed phase thermography has been proven effective on depth retrieval of flat bottomed holes in materials such as plastics and aluminum. In pulsed phase thermography, amplitude and phase delay signatures are available following data acquisition, by applying a transformation algorithm such as the Fourier transform on thermal profiles obtained by pulsed thermography. Following earlier work by two of the authors (an extended review on pulsed phase thermography theory including a new inversion technique for depth retrieval by correlating the depth with the blind frequency fb [frequency at which a discontinuity produces enough phase contrast to be detected]), in this paper,steel plates containing flat bottomed holes at different depths (from 1 to 4.5 mm [0.04 to 0.18 in.]) were tested by quantitative pulsed phase thermography. Least squares regression results showed excellent agreement between depth and the inverse square root blind frequency, which can be used for depth inversion. Experimental results on steel plates with simulated corrosion are also presented. It is worth noting that, in some cases, results were improved by performing pulsed phase thermography on reconstructed (synthetic) rather than on raw thermal data. [ABSTRACT FROM AUTHOR]

In this work, active infrared thermography was employed in the investigation of various building materials. Different types of building materials were assessed: three types of porous stone (from Rhodes, Cyprus and Rethymno-Crete) and one type of marble (Dionysus). The investigated samples contained self-induced discontinuities of known dimensions and depths. During the investigation, the specimens were heated externally (thermal excitation) and thermograms were recorded continuously at the transient phase. Mathematical thermal modeling enabling the modeling of the investigated subsurface discontinuities, using 3D software, was also implemented. Then, quantification analysis (that is, temperature versus time plots, as well as thermal contrast curves) from the experimental tests, as well as from the use of thermal modeling runs took place, indicating the thermal behavior of building materials containing such discontinuities. [ABSTRACT FROM AUTHOR]

In this talk the concepts of thermography inspection of structures using a drone are discussed including benefits, challenges, case studies. Approaches for thermogram processing based on deep learning and the possible addition of a visible channel combined with proper data fusion are overviewed as well. Recent aircrafts incorporate an high content of composite materials such as Carbon Fiber Reinforced Plastic (CFRP) used in wings, fuselage, etc. Such materials require proper inspection to detect and assess severity of embedded defects present at manufacturing stages such as porosities and in-service defects (delaminations and disbonds). Since surfaces to inspect are large and time for inspection should be limited as much as possible, quick inspection schemes are preferred. Many other fields could benefit from thermographic drone NDT, for instance civil engineering with large structures sometimes difficult and dangerous to reach. Finally, some case studies are presented including a flying demonstrator as well. [ABSTRACT FROM AUTHOR]