Application of shearography with thermal loading for structural inspection of Rembrandt’s Night Watch

The assessment of the structural condition of cultural heritage objects is important for conservation interventions and their long-term preservation. This investigation concerns The Night Watch (1642), a large-format 17^th-century canvas painting by Rembrandt van Rijn that is on display in the Rijksmuseum, Amsterdam. This painting,...

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...

Shearography non-destructive testing of a composite ship hull section subjected to multiple impacts

The use of thick composites and sandwich structures is increasing rapidly in marine, aerospace, and wind energy industries [1–3]. For example in the marine sector, sandwich structures consisting of glassfiber laminate skins bonded to a foam core are attractive because of the advantages of being light-weight, resistant to corrosion and underwater...

Spatially modulated thermal excitations for shearography non-destructive inspection of thick composites

With the increasing application of thick composites in marine, wind energy and aerospace industries, the inspection of thick composites becomes more and more challenging when considering the variety of thick structures (e.g., laminate, sandwich, honeycomb structures). Shearography is a full-field and non-contact optical non-destructive...

Three-dimensional spectral measurements of paint samples using optical coherence tomography

In this study, we describe a method for measuring the spectral reflectance of a paint layer at both the surface and in the volume of the paint layers. We first present a fringes model which illustrates the possibilities for spectral reconstruction using a Short-Time-Fourier-Transform algorithm. We investigate the remaing percentage errors and...

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...

Spectra stitching for ultra-high resolution, low sensitivity decay and high-speed SD-OCT

In this study we investigate the possibility of spectra stitching in the context of Spectral Domain - Optical Coherence Tomography (SD-OCT). The aim is to reach a high axial resolution while keeping sampling issues to a low level (slow decay in depth) but still operating with the fastest camera line rate available. The paper focuses mainly on...

Analysis of a SD-OCT-based hyperspectral system for spectral reflectance measurements

In this study, we compare the hyperspectral imaging capabilities of a custom-built visible light OCT with those of a commercial grade hyperspectral camera. Using the Short-Time-Fourier-Transform algorithm on the OCT signal, we estimate the variation in the surface spectral response from two paint pigments. Our study aims at comparing the...

EXTREME shearography: High-speed shearography instrument for in-plane surface strain measurements during an impact event

This work presents the design and the latest experimental results on the surface strain measurements during an impact event obtained with the EXTREME high-speed shearography instrument. The shearography technique is used in this project to provide a quantitative measurement of the surface strain development at the first moments of the impact...

EXTREME shearography: Development of a high-speed shearography instrument for measurements of the surface strain components during an impact event

This work presents the design and preliminary results of a high-speed shearography instrument in development for surface strain components measurements during an impact event. Composite materials are vulnerable to extreme dynamic loadings such as blade off events or foreign object damage as their mechanical properties are strain rate...

Development of the 3D Shape Shearography Technique for Strain Inspection of Curved Objects

Practical development questions of 3D shape shearography technique for surface strain inspection of curved objects are discussed. Results of a global cameras-projector system calibration and different methods of shear distance estimation in 3D are presented

Evaluating delamination growth in composites under dynamic loading using infrared thermography

In this paper, a method has been developed to use thermography for the quantitative analysis of a delamination area under dynamic loading. To demonstrate this method, a coupon was developed with double shear configuration and an initial delamination consisting of a PTFE insert. The coupon was tested under fatigue loading and an infrared (IR)...

3D shape shearography with integrated structured light projection for strain inspection of curved objects

Shearography (speckle pattern shearing interferometry) is a non-destructive testing technique that provides full-field surface strain characterization. Although real-life objects especially in aerospace, transport or cultural heritage are not flat (e.g. aircraft leading edges or sculptures), their inspection with shearography is of interest for...

Strain characterization of embedded aerospace smart materials using shearography

The development of smart materials for embedding in aerospace composites provides enhanced functionality for future aircraft structures. Critical flight conditions like icing of the leading edges can affect the aircraft functionality and controllability. Hence, anti-icing and de-icing capabilities are used. In case of leading edges made of fibre...