1,721,082 research outputs found
EFFECT OF FIBER REINFORCEMENT ON THE LOW VELOCITY IMPACT BEHAVIOR OF WOVEN FABRIC REINFORCED COMPOSITES: INTEGRATED CONTRIBUTION OF THE THERMOGRAPHIC, INTERFEROMETRIC AND SPECKLE INSPECTIONS
No full textLike parts or structures assembled from common isotropic engineering materials,
fiber reinforced composites can be subjected to impact loading during their service life. Fiber
composites have, nevertheless, a unique interaction with the externally applied load, since
severe internal damage can be generated without any external sign. In fact, several damage
mechanisms can be operating, viz. matrix cracking, fiber breakage, fiber pullout, fiber-matrix
interface rupture and delamination. The challenge of non-destructive quality control is to
establish safe boundaries for the use of a composite part or structure, which has been
subjected to an impact event not causing non-repairable failure. For the range of possible
impact velocities many parameters could be involved on the composite response, such as the
mass and the geometry of the impactor; the laminate stacking sequence; among others, the
kind, architecture and volume of reinforcement fibers. In our work, we have focused our
attention on two woven fabric reinforced composites: one reinforced with E-glass fibers and the other with basalt ones, both subjected to low velocity impact at different energies. Basaltfibers are produced from basalt rock using single component raw material by drawing and
winding fibers from the melt. Once the basalt fibers have been produced, they are
transformed into a suitable form for particular application. Basalt fibers is a contemporary
material, which combines ecological safety, natural longevity, and fire safety
(incombustibility). Water-absorbing capacity of basalt fiber is much less than 1%, of
fiberglass – up to 10-20%. For comparison, industrially manufactured fiberglass, before
chemical sizing, absorbs substantial amount of moisture in humid air, which weakens its
physical-technical and longevity properties and eventually leads to fiber damage. In contrast,
low non-volatile water absorbency of basalt fiber ensures stability of thermal and physical
characteristics in case of continuous service. Basalt fibers have high chemical stability and
pertain to the first dimming class and greatly exceed fiberglass as regards acid, alkali and
steam resistance. Basalt fibers composites may have a longer operating life as compared to
glass fiber composites and are ideally suited for demanding applications requiring high
temperatures, chemical resistance, durability, mechanical strength and low water absorption.
Infrared thermography techniques have proven to be an effective way to detect and quantify
the degree of surface and subsurface damage on such components. In this work, an external
source of energy (a lamp of 500 W in reflection mode) is used to produce a thermal contrast
between the non-defective and the defective material. The experimental results presented
herein demonstrate that is possible to detect delamination-type defects and to assess the
impact severity on composite materials with glass and basalt fibers through active
thermography techniques, specifically Square Pulse Thermography (SPT). Digital Speckle
Photography (DSP) and Holographic Interferometry (HI) were performed as well with the
intention of providing supplementary and integrated results
Holographic interferometry (HI), infrared Vision and X-Ray fluorescence (XRF) spectroscopy for the assessment of painted wooden statues : a new integrated approach
No full textWood has been routinely employed in decorative arts, as well as in sculptures and paintings (support) during the Middle Ages, because of its unique aesthetic virtues. It may safely be assumed that wood, as a material for monumental sculpture, was much more commonly employed in the mediaeval period than existing examples would seem to indicate (Bulletin of the metropolitan Museum of Art, 2013). Wood is easily obtainable; it could be carved and put in place with less difficulty than stone, it is chemically stable when dry, and its surface offers a compatible substrate for paint application. However, the use of wood is not without pitfalls, and requires an understanding of its anisotropic and hygroscopic nature. It is also dimensionally unstable and subject to deterioration by fungi and insects. Moisture-related dimensional changes are certainly among the most challenging problems in painting conservation. With the purpose of preventing important damages, the use of non-or microdestructive testing (NDT) techniques is undoubtedly of paramount interest for painted wooden statues of great value. This work has a threefold purpose: (1) to validate the effectiveness of an integrated approach using near-infrared (NIR) reflectography, square pulse thermography (SPT), and holographic interferometry (HI) techniques for discovering old repairs and/or inclusions of foreign materials in a wooden structure, (2) to confirm and approximately date the restoration carried out by x-ray fluorescence (XRF) spectroscopy and energy-dispersive x-ray spectroscopy (EDS) (that is assembled with a scanning electron microscopy—SEM) techniques, and (3) to combine into a multidisciplinary approach two quantitative NDT results coming from optical and thermographic methods. The subject of the present study was a statue named “Virgin with her Child” (XIV century), whose origins are mysterious and not properly documented
Non-destructive testing techniques to help the restoration of frescoes
No full textAmong the several issues to be considered during fresco’s restoration, the understanding of the effectiveness of the intervention, the identification of the main chemical elements used in previous restorations and the attention to weak areas of the building structure, adjacent to frescoes, are of paramount importance. This work describes an integrated, non-destructive testing approach focusing on these three main issues. In particular, two frescoes of Giacomo Farelli are analyzed herein. These artworks were affected by a strong earthquake in 2009, which had a heavy impact on several cultural heritage objects in L’Aquila (Italy), including on the Santa Maria della Croce di Roio Church (1625), where these two frescoes are located. One of the frescoes, which underwent a restoring before the quake, was previously tested by electronic speckle pattern interferometry (ESPI) before and after the restoration. These previous results are compared with new measurements carried out after the 2009 earthquake using infrared thermography (IRT). The combined approach, ESPI-IRT, clearly highlighted that the structure of the frescoes was significantly affected by the earthquake, since the old subsurface cracks, restored before 2009, were once again evident after the earthquake. In addition, the presence of a subsurface niche containing an ancient statue, also detected by means of IRT, might contribute to increase the severity of the damages. Finally, the joint examination of these frescoes using near-infrared reflectography and X-ray diffractometry was crucial to confirm the presence of a radioactive chemical element in the wall painting
Santa Maria di Collemaggio Church (L’Aquila, Italy) : historical reconstruction by non-destructive testing techniques
No full textThe main goal of this work was the non-destructive testing (NDT) of an ancient fresco (15th century) preserved in the Santa Maria di Collemaggio Church (L’Aquila, Italy) and damaged after the 2009 earthquake. Active infrared thermography (IRT), near-infrared (NIR) reflectography and ultraviolet imaging (UV) were used. In addition, the state of the fresco prior to the earthquake was analyzed by electronic speckle pattern interferometry (ESPI), digital speckle correlation (DSC), raking light, tap, and chemical NDT techniques. The use of these techniques was important for the monitoring of new damages and for a comparison between the results over the years. Square heating thermography (SHT) data were processed using principal component thermography (PCT) and pulsed phase thermography (PPT) algorithms, in order to improve the defects’ signature and to reduce the impact of non-uniform heating and emissivity variations due to the painting’s pigments. A multi-analysis approach, segmentation operators and a specific data correlation method emphasize the overall study of the fresco. Furthermore, the facade and the high altar area were inspected by passive thermography and ground-penetrating radar (GPR), respectively. In the present case, the combined use of NDT techniques was useful to fill in the gaps in the construction history of the building
Thermal NDT applying Candid Covariance-Free Incremental Principal Component Thermography (CCIPCT)
No full textThermal and infrared imagery creates considerable developments in Non-destructive Testing (NDT) area. An
analysis for thermal NDT inspection is addressed applying a new technique for computation of eigen-decomposition
(factor analysis) similar to Principal Component Thermography(PCT). It is referred as Candid Covariance-Free
Incremental Principal Component Thermography (CCIPCT). The proposed approach uses a computational
short-cut to estimate covariance matrix and Singular Value Decomposition(SVD) to obtain faster PCT results,
but while the dimension of the data increases. The problem of computational cost for high-dimensional thermal
image acquisition is also investigated. Three types of specimens (CFRP, plexiglass and aluminum) have been
used for comparative benchmarking. Then, a clustering algorithm segments the defect at the surface of the
specimens. The results conclusively indicate the promising performance and demonstrated a conrmation for
the outlined properties
Pulsed phase thermography inversion procedure using normalized parameters to account for defect size variations
No full textDefect Detection in Wind Turbine Blades Using Infrared Thermography, Image Processing, and U-Net
No full textIn this research, we developed and tested an automated defect detection system for wind turbine blades using infrared thermography (IRT) and the deep learning model U-Net
University Laval Infrared Thermography Databases for Deep Learning Multiple Types of Defect Detections Training
No full textNowadays, automatic defect detection research by deep learning algorithms plays a crucial role, especially for non-destructive evaluation with infrared thermography. In deep learning research, the databases are the Achilles’ heel during the training in order to preserve optimized performance. In this work, we will present the infrared thermography sequences databases from the Universite Laval Multipolar Infrared Vision Infrarouge Multipolaire (MIVIM) research group for regular and irregular defect analysis in order to provide the best data collection resources for the pretraining of convolutional neural network and feature extraction analysis with future researchers and engineers. The databases will include infrared thermography sequences from regular and irregular defects of carbon fiber-reinforced polymer (CFRP), glass fiber-reinforced polymer (GFRP), plexiglass, aluminum, and steel, which could be available online for public use and research purposes
Falling weight impacted glass and basalt fibre woven composites inspected using non-destructive techniques
No full textA limited number of comparative studies on falling weight impact properties of different composites exist, especially using non-destructive techniques (NDTs). In this work, two types of woven fabric composites, reinforced respectively with E-glass fibres and basalt fibres, were subjected to low velocity impact at different energies (7.5, 15 and 22.5 J). Comparative indications were offered by impact hysteresis cycles and the integration of data between different enhanced vision methods, namely interferometric and IR thermographic techniques. The integrated application of these techniques suggests that the increased directionality of impact damage observed in basalt fibre reinforced composites, though their impact performance appears to be slightly superior, may represent a limitation on the predictability of their behaviour
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