Four-flux model combined with optical coherence tomography technique for non-destructive testing of the colour ground layers of the paintings

The colour of the ground layers of a painting has an influence on its visual appearance. In addition to the commonly used white ground layers, other colour ground layers have been used, for example, the grey ground layer used in Peter Paul Rubens’s painting Portrait of Clara Serena Rubens helps the colour transition of the skin tones....

Comparative performance of high and medium resolution cameras for defect detection in carbon-fiber reinforced composites by digital shearography

The performance of defect detection in composite materials using digital shearography is important for correct decision-making in non-destructive testing. In this work, we compared a high-resolution 24-megapixel digital still camera (DSLR) and a conventional medium-resolution 5-megapixel camera to determine the detectability of blind holes in...

Application of shearography and the percussion method for the structural inspection of wall paintings: A case study of St. Christopher in Maria Church, Nisse

Structural delamination in mural paintings is a complex phenomenon and is considered among the most frequent types of damage. In conservation practice, the most common technique to identify structural detachments is the percussion method. Full-field optical techniques based on interferometry, such as shearography, can provide a more...

Investigations on Explainable Artificial Intelligence methods for the deep learning classification of fibre layup defect in the automated composite manufacturing

Automated fibre layup techniques are widely used in the aviation sector for the efficient production of composite components. However, the required manual inspection can take up to 50 % of the manufacturing time. The automated classification of fibre layup defects with Neural Networks potentially increases the inspection efficiency. However,...

3.12 Inspection and Monitoring of Composite Aircraft Structures

The new generation of civil aircraft, including the Airbus A380 and the Boeing 787, are composed of composite materials for their primary aircraft structures. This presents a challenge for airline maintenance, repair, and overhaul (MRO) operations in both the short- and long-term. In the short-term, new technologies are needed for maintenance,...

Friction stir weld-bonding defect inspection using phased array ultrasonic testing

Weight reduction is an important driver of the aerospace industry, which encourages the development of lightweight joining techniques to substitute rivet joints. Friction stir welding (FSW) is a solid-state process that enables the production of lighter joints with a small performance reduction compared to the base material properties....

Post peel test assessment of metal-metal bonded interface using hyperspectral imaging

The adhesion process of bonded structures is a very sensitive manufacturing process, namely to surface contaminations. Nowadays, the adhesion quality of bonded joints can only be detected by destructive testing such as peel tests. But, for actual structures destructive testing of every bonded part is obviously not an option and industry is...

Monitoring chemical degradation of thermally cycled glass-fibre composites using hyperspectral imaging

Nowadays, the application of glass-fibre composites in light-weight structures is growing. Although mechanical characterizations of those structures are commonly performed in testing, chemical changes of materials under stresses have not yet been well documented. In the present work coupon tests and Hyperspectral Imaging (HSI) have been used to...

Optical coherence tomography complemented by hyperspectral imaging for the study of protective wood coatings

Optical coherence tomography (OCT) is a contactless and non-destructive testing (NDT) technique based on lowcoherence interferometry. It has recently become a popular NDT-tool for evaluating cultural heritage. In this study, protective coatings on wood and their penetration into the wood structure were measured with a customized infrared fiber...

Phase discontinuity predictions using a machine-learning trained kernel

Phase unwrapping is one of the key steps of interferogram analysis, and its accuracy relies primarily on the correct identification of phase discontinuities. This can be especially challenging for inherently noisy phase fields, such as those produced through shearography and other speckle-based interferometry techniques. We showed in a recent...

Optical coherence elastography for measuring the deformation within glass fiber composite

Optical coherence elastography (OCE) has been applied to the study of microscopic deformation in biological tissue under compressive stress for more than a decade. In this paper, OCE has been extended for the first time, to the best of our knowledge, to deformation measurement in a glass fiber composite in the field of nondestructive testing. A...

Shearography technology and applications: A review

Shearography is a full-field speckle interferometric technique used to determine surface displacement derivatives. For an interferometric technique, shearography is particularly resilient to environmental disturbances and has hence become an invaluable measurement tool outside of the optics laboratory. Furthermore, the inclusion of additional...