Eleni Cheilakou

Intelligent system for cultural objects identification, damage assessment and restoration

Cultural objects and art works need ongoing conservation interventions in order to be available for the next generations. The most object-friendly analysis approaches are based on non-destructive techniques (NDTs) that allow both the materials characterisation as well as the decay detection of cultural artefacts. Non-destructive testing and evaluation includes the employment of several methods such as the well-established technique of diffuse reflectance spectroscopy with fibre optics (FORS). Such techniques produce output with multiple series of data for multiple different pigment used in objects. In this work, we present a data management solution that contributes with: 1) a library of known reference pigments/colours; 2) a proposed pattern matching technique that allows the automatic classification of any new pigment. The experimental evaluation results show that the data processing proposed is effective. Feedback is particularly encouraging as it allows automation and therefore radically decreased time for pigment/colour matching and identification.

Data Engineering for Materials Identification, Damage Assessment and Restoration of Cultural Objects

Cultural objects and art works need ongoing conservation interventions in order to be available for the generations to come. The most object-friendly analysis approaches are based on non destructive techniques NDTs that allow both the materials characterization/evaluation as well as the decay detection and assessment of cultural artifacts. Non destructive testing and evaluation includes the employment of several methods such as the well-established technique of Diffuse Reflectance Spectroscopy with Fiber Optics FORS. FORS allows the reflectance spectral analysis of the pigments used in artifacts, which leads to their identification. Such techniques produce output with large volumes of data for each different pigment used in objects. In this work, we present a data management solution that contributes with 1 a library of known reference pigments/colors of archaeological objects along with 2 a proposed novel pattern matching technique that allows the automatic classification of any new pigment that is recovered from cultural objects using the FORS measurements. The proposed technique is based on a k-NN classifier. The experimental evaluation results of the proposed technique show that the data processing proposed is both effective and efficient. Feedback for the proposed approach is particularly encouraging as it allows automation and therefore radically decreased time for pigment/color matching and identification.

Standardizing NDT& E Techniques and Conservation Metadata for Cultural Artifacts

Conservation activities, before and after decay detection, are considered as a prerequisite for maintaining cultural artifacts in their initial/original form. Taking into account the strict regulations where sampling from art works of great historical value is restricted or in many cases prohibited, the application of Non-Destructive Testing techniques (NDTs) during the conservation or even decay detection is highly appreciated by conservators. Non-destructive examination include the employment of multiple analysis approaches and techniques namely Infrared Thermography (IRT), Ultrasonics (US), Ground Penetrating Radar (GPR), VIS–NIR Fiber Optics Diffuse Reflectance Spectroscopy (FORS), portable X-Ray Fluorescence (XRF), Environmental Scanning Electron Microscopy with Energy Dispersive X-Ray Analysis (ESEM-EDX), Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and micro-Raman Spectroscopy. These produce a huge amount of data, in different formats, such as text, numerical sets and visual objects (i.e. images, thermograms, radargrams, spectral data, graphs, etc). Moreover, conservation documentation presents major drawbacks, as fragmentation and incomplete description of the related information is usually the case. Assigning conservation data to the objects’ metadata collection is very rare and not yet standardized. The Doc-Culture Project aims to provide solutions for the NDT application methodologies, analysis and process along with their output data and all related conservation documentation. The preliminary results are discussed in this paper.

Comparative evaluation of aerospace composites using thermography and ultrasonic NDT techniques

In the present research work a study was carried out evaluating the applicability of two NDT techniques, this of Transient Thermography (TT) and Ultrasonic Testing (UT) for the inspection of different types of composite materials (i.e. laminated CFRPs, laminated hybrid FRPs and sandwiched panels). The composite structures were consisted of a variety of artificial defects, while inspection was performed through different testing configurations. In particular, transient thermography was implemented through the monitoring of the surface transient cooling after flash heating the samples and ultrasonic testing was applied using both a conventional single element probe (immersion technique) and a linear phased array transducer consisted of 128 elements. The main objective of this work was to compare the applicability and effectiveness of the two techniques in aerospace composites inspection as well as to evaluate the accuracy produced regarding the quantitative characterisation of the detected features. The obtained results showed that all the defects were revealed by either transient thermography or ultrasonic testing, whilst thermographic inspection can display the acquired results in a more rapid manner. On the other hand UT testing can provide efficient results for deeper probing requiring however longer inspection times. In other words, the acquired data and the respective analyses highlighted the different capability of each testing configuration, to detect defects and to gain knowledge for the interior of the structures.

3D mapping of reinforcement and tendon ducts on pre-stressed concrete bridges by means of Ground Penetrating Radar (GPR)

The present study evaluates the potential of GPR for the inspection of pre-stressed concrete bridges and its usefulness to provide non visible information of the interior structural geometry and condition, required for strengthening and rehabilitation purposes. For that purpose, different concrete blocks of varying dimensions with embedded steel reinforcement bars, tendon ducts and fabricated voids, were prepared and tested by means of GPR in a controlled laboratory environment. 2D data acquisition was carried out in reflection mode along single profile lines of the samples in order to locate the internal structural elements. 3D surveys were also performed in a grid format both along horizontal and vertical lines, and the individual profiles collected were interpolated and further processed using a 3D reconstruction software, in order to provide a detailed insight into the concrete structure. The obtained 2D profiles provided the accurate depth and position of the embedded rebars and tendon ducts, verifying the original drawings. 3D data cubes were created enabling the presentation of depth slices and providing additional information such as shape and localization of the internal elements. The results obtained from this work showed the effectiveness and reliability of the GPR technique for pre-stressed concrete bridge investigations.

LWIR and MWIR thermography tools for composites assessment

Smart methods for assessing the integrity of a composite structure are essential to both reduce manufacturing costs and out of service time of the structure due to maintenance. Nowadays, thermal non-destructive testing (NDT) is commonly used for assessing composites. This research work evaluates the potential of various infrared thermography (IRT) approaches for assessing different types of fabricated defects (i.e. impact damage, inclusions for delaminations, etc) on Glass Fibre Reinforced Polymer (GFRP) and Carbon Fibre Reinforced Polymer (CFRP) plates. Measurements were performed using LWIR and three active approaches: a) pulsed thermography using the flash method (xenon flash lamps), b) transient themography using IR-heating pulse, and c) thermographic inspection for cooled sample by freezing in -20 °C and then use monitoring. Furthermore, integrated flash thermography by employing a MWIR system was also used.

Nondestructive testing of plastered mosaics with the use of active thermography approaches

In this work, different mosaics covered with various plasters (of thickness and compositions) were evaluated in lab by means of active long wave and mid wave thermography approaches, with the intention of detecting the tesserae beneath the plastered surface. Thermal images as well as thermal contrast curves between plastered surfaces and plastered mosaics were recorded. Special considerations concerning the applicability and accuracy of the used approaches for this specific application are presented. Results from the assessment are presented and discussed, indicating that images seeing through the mortar-plaster on plastered mosaic surfaces can be obtained using active thermography approaches.