Innovative Non-destructive Techniques Research Articles

Delamination Assessment in Composite Laminates through Local Impulse Excitation Technique (IET)

This paper deals with an innovative nondestructive technique for composites (local-IET), which is based on the Impulse Excitation Technique (IET) and, in the presence of damage, assesses the degradation of the elastic properties of a local region of the laminate by reversibly clamping its boundaries. In this paper, a numerical analysis of the sensitivity of the local-IET to the delamination damage mechanism is conducted. Firstly, a Finite Element (FE) model of the local-IET test is determined through experimental investigations on undamaged composite laminates, which cover a wide range and are made of glass or carbon fibers, through resin infusion or pre-preg consolidation and with unidirectional or fabric textures. The vibrational response of a glass fiber composite with local delamination is then assessed with the local-IET. By modeling the delamination in the simulation environment, the effectiveness of the FE model in replicating the vibrational response, even in the presence of delamination, is shown through a comparison with the experimental results. Finally, the FE model is exploited to perform a sensitivity analysis, showing that the technique is able to detect the presence of delamination.

A Non-Destructive Methodology for the Viscoelastic Characterization of Polymers: Toward the Identification of the Time-Temperature Superposition Shift Law.

Polymers find widespread applications in various industries, such as civil engineering, aerospace, and industrial machinery, contributing to vibration control, dampening, and insulation. To accurately design products that are able to predict their dynamic behavior in the virtual environment, it is essential to understand and reproduce their viscoelastic properties via material physical modeling. While Dynamic Mechanical Analysis (DMA) has traditionally been used, innovative non-destructive techniques are emerging for characterizing components and monitoring their performance without deconstructing them. In this context, the Time-Temperature Superposition Principle (TTSP) represents a powerful empirical procedure to extend a polymer's viscoelastic behavior across a wider frequency range. This study focuses on replicating an indentation test on viscoelastic materials using the non-destructive Viscoelasticity Evaluation System evolved (VESevo) tool. The primary objective is to derive a unique temperature-frequency relationship, referred to as a "shift law", using characteristic curves from this non-invasive approach. Encouragingly, modifying the device setup enabled us to replicate, virtually, three tests under identical initial conditions but with varying indentation frequencies. This highlights the tool's ability to conduct material testing across a range of frequencies. These findings set the stage for our upcoming experiment campaign, aiming to create an innovative shift algorithm from at least three distinct master curves at specific frequencies, offering a significant breakthrough in non-destructive polymer characterization with broad industrial potential.

Assessing the expansion and success of a restored population of Gongolaria barbata (Stackhouse) Kuntze (Fucales, Phaeophyceae) using high-precision positioning tools and size distribution frequencies

Ongoing human pressures over recent decades have caused the loss and ensuing impoverishment of the complexity and diversity of Mediterranean habitats dominated by algal species of the order Fucales. Gongolaria barbata, a habitat-forming Fucales species that has disappeared in several places across the Mediterranean, was reintroduced in a cove (Cala Teulera, Maó Bay, Menorca) where it was known to have been locally extinct for more than 40 years. Reintroduction was performed in 2011 using innovative non-destructive techniques. Here we describe the expansion patterns of the population ten years after its reintroduction, and we look at the size-structure distribution of the restored population compared to one of the only natural populations known in Spain (Fornells Bay, Menorca). Newly settled individuals exhibit a progressive dispersal pattern from restoration sites, favouring rocky substrates at the shallowest level parallel to the shore. The area occupied by G. barbata has increased by almost three orders of magnitude in ten years, from approximately 3.6 m2 of the initially restored area to a current restored area of 2093 m2. Recruits and juveniles dominate the restored population but some individuals have reached large size classes, the overall size distribution resembling the reference population. The high-resolution cartography included in our study enables an accurate mid to long-term assessment of the expansion of G. barbata. Incorporating such tools in restored marine forests would facilitate the implementation of efficient management policies that will help reinforce their conservation

Residual elastic response in damaged woven laminates through local Impulse Excitation Technique

In this work, the assessment of the residual elastic response in damaged woven laminates is addressed through an innovative nondestructive technique. Based on the Impulse Excitation Technique (IET), the goal is to determine the local variation of the elastic properties through local vibrational tests. In particular, by non-destructively clamping its extremities, the vibrational response of the region of interest can be isolated and a vibrational mode can be excited, which depends only on the material properties of the inspected region. In presence of damage, the local degradation of the elastic response can be then correlated to the decrement of the first resonant frequency. The technique is applied to glass-fibre/epoxy laminates damaged by impact and its sensitivity to the size of the inspected region is investigated through three clamping devices of different dimensions. For validation, tensile tests are performed on specimens cut from the impacted plates, where the axial deformation is punctually measured through optic fibre glued along the specimen axis. Results show that the residual elastic properties assessed with the proposed technique are in very good agreement with those measured through the optic fibre, thus proving the effectiveness of the methodology.

Terahertz probing of low‐temperature degradation in zirconia bioceramics

AbstractZrO2‐based ceramics are widely used in biomedical applications due to its color, biocompatibility, and excellent mechanical properties. However, low‐temperature degradation (LTD) introduces a potential risk for long‐term reliability of these materials. The development of innovative nondestructive techniques, which can explore LTD in zirconia‐derived compounds, is strongly required. Yttria stabilized zirconia, 3Y‐TZP, is one of the well‐developed ZrO2‐based ceramics with improved resistance to LTD for dental crown and implant applications. Here, 3Y‐TZP ceramic powders were pressed and sintered to study the LTD phenomenon by phase transition behavior. The LTD‐driven tetragonal‐to‐monoclinic phase transition was confirmed by XRD. XPS analysis demonstrated that induced LTD reduced the oxygen vacancies which supports these findings. It is proved that after the degradation, the 3Y‐TZP ceramics show the decreased dielectric permittivity at terahertz frequencies due to the crystallographic phase transformation. Terahertz nondestructive probe is a promising method to investigate LTD in zirconia ceramics.

Postharvest Water Loss of Wine Grape: When, What and Why.

In postharvest science, water loss is always considered a negative factor threatening fruit and vegetable quality, but in the wine field, this physical process is employed to provide high-quality wine, such as Amarone and Passito wines. The main reason for this is the significant metabolic changes occurring during wine grape water loss, changes that are highly dependent on the specific water loss rate and level, as well as the ambient conditions under which grapes are kept to achieve dehydration. In this review, hints on the main techniques used to induce postharvest wine grape water loss and information on the most important metabolic changes occurring in grape berries during water loss are reported. The quality of wines produced from dried/dehydrated/withered grapes is also discussed, together with an update on the application of innovative non-destructive techniques in the wine sector. A wide survey of the scientific papers published all over the world on the topic has been carried out.

A new application of Fiber optics reflection spectroscopy (FORS): Identification of “bronze disease” induced corrosion products on ancient bronzes

Fiber Optics Reflectance Spectroscopy (FORS) has been widely used in the field of cultural heritage for material identification. Nevertheless, it had been rarely applied in the study of bronze corrosion products. This paper aims at exploring the potential of FORS on corrosion products analysis, proposing it as an innovative non-destructive technique for the condition assessment of bronze artefacts in museum collections. A gilded bronze statue “Vajrasattva Bodhisattva” dated to the Ming dynasty (A. D. 1368-1644) from National Museum of China was investigated. The in-situ FORS analysis was conducted on 36 points, revealing copper trihydroxychloride (atacamite/clinoatacamite) and chalconatronite as two major types of corrosion products. This result was double-confirmed by Raman and XRD analyses of 10 samples taken from these points. It proves that FORS is a very promising technique for non-destructive in-situ detection of chloride-bearing bronze corrosions. It may revolutionize the way of screening artefacts with bronze disease, helping conservators get the distribution “map” of different bronze corrosion quickly and comprehensively, and making appropriate treatment proposals accordingly.

Experimental measurements through ultrasounds for viscoelasticity analysis

Among the different methodologies useful to determinate polymers viscoelastic properties in literature, it is possible to find some different techniques based on the ultrasounds pulse-echo methods which show several limits in the properties estimation of the tested materials. In this scenario, the proposed manuscript focuses on an innovative non-destructive technique of viscoelastic materials by means of ultrasounds, which could be suitably employed on polymers. The developed procedure is aimed to evaluate the material response in terms of loss factor within different temperatures and induced excitation frequencies. To carry out the viscoelasticity analysis through ultrasounds, a bench has been set up and the data acquisition has been performed by means of the pulse-echo method on three different tires tread specimens and, then, a post-process algorithm has been implemented in order to determine the viscoelastic behavior in terms of loss factor. The comparison of the achieved results with the temperature sweep master curves, which were determined by means of standard Dynamic Mechanical Analysis (D.M.A.) testing on the same polymers, has provided an indication of the goodness of the proposed procedure.

An innovative nondestructive technique for the local assessment of residual elastic properties in laminated composites

In this work, an innovative experimental methodology is presented for the assessment of damage severity in composites. The technique aims at determining the local variation of the elastic properties in the damaged region of a composite component. Based on the Impulse Excitation Technique (IET), the vibrational response of the inspected region is isolated by clamping its extremities through vacuum, thus allowing the assessment of local variations. Complementarily, a new analytical approach is derived for the assessment of the residual elastic properties of the damaged area from the measurement of the first resonant frequency. Validation of the proposed methodology is performed on two glass-fibre woven fabric composites, damaged by impact. The material properties of the damaged zone determined through the proposed technique are compared to the results of tensile tests performed on specimens cut from the impacted plates. In particular, the specimens are equipped with optic fibre in order to punctually measure the elastic parameters. Results show that the residual elastic properties assessed with the proposed technique are in very good agreement with those measured through the optic fibre, thus proving the effectiveness of the methodology.

A Novel Infrared Thermography Sensing Approach for Rapid, Quantitative Assessment of Damage in Aircraft Composites.

The current necessity of the scientific and industrial community, for reduction of aircraft maintenance cost and duration, prioritizes the need for development of innovative nondestructive techniques enabling fast and reliable defect detection on aircraft fuselage and wing skin parts. Herein, a new low-cost thermographic strategy, termed Pulsed Phase-Informed Lock-in Thermography, operating on the synergy of two independent, active infrared thermography techniques, is reported for the fast and quantitative assessment of superficial and subsurface damage in aircraft-grade composite materials. The two-step approach relies on the fast, initial qualitative assessment, by Pulsed Phase Thermography, of defect location and the identification of the optimal material-intrinsic frequency, over which lock-in thermography is subsequently applied for the quantification of the damage’s dilatational characteristics. A state-of-the-art ultra-compact infrared thermography module envisioned to form part of a fully-automated autonomous nondestructive testing inspection solution for aircraft was conceived, developed, and tested on aircraft-grade composite specimens with impact damages induced at variable energy levels and on a full-scale aircraft fuselage skin composite panel. The latter task was performed in semi-automated mode with the infrared thermography module mounted on the prototype autonomous vortex robot platform. The timescale requirement for a full assessment of damage(s) within the sensor’s field of view is of the order of 60 s which, in combination with the high precision of the methodology, unfolds unprecedented potential towards the reduction in duration and costs of tactical aircraft maintenance, optimization of efficiency and minimization of accidents.

Multi-scale laboratory routine in the efficacy assessment of conservative products for natural stones

The evaluation of conservative treatments’ efficacy on natural building stones are usually based on standard recommendation routines finalized to evaluate compatibility and harmfulness of products in turn of the substrate. However, the visualization and the quantification of products inside pore structure of natural stones is not immediate through standard tests, so that imaging and advanced techniques are recently proposed in material conservation field to improve knowledge on penetration depth, modification of pore-air interface at different scale and monitor dynamic absorption processes. Moreover, natural stones are usually characterized by complex structure, which changes due to conservative treatments have to be inspected at different scale (from micrometer to nanometer).In this prospective, the assessment of laboratory practices able to integrate multiscale methods and give back a complete overview on interaction between new conservative formulates and natural stones is of high interest.In this paper, we propose a methodological routine for efficacy assessment of conservative products, incorporating classical and innovative nondestructive techniques. Validation of the workflow has been verified on a high porous natural stone treated with new hybrid formulates appropriately customized for conservation issues.•The study intends to add new insights on problems related to consolidation of high porous carbonate stone, application methods in consolidating natural stones and methods to evaluate efficacy of new products.•A multi-scale laboratory investigation procedure is proposed by integrating standard and innovative nondestructive methods. Merits and limits of each applied method are discussed during validation.•The possibility to incorporate standard routines and/or substitute destructive testing with non-destructive ones seem to be a valid alternative to evaluate efficiency and monitor behavior of stones treated with consolidating products.

Ascertaining the degradation state of ceramic tiles: A preliminary non-destructive step in view of conservation treatments

Conserving the cultural heritage is a general concern and the use of non-destructive techniques to characterize ancient materials is important. Serious deterioration effects in environmentally exposed ancient glazed ceramic tiles arise from the development of micro-organisms (algae/fungi) within the pore system. Subsequent biodegradation processes are particularly harmful once the decorated glaze is damaged by exfoliation/detachment.Three case studies will be addressed: Portuguese polychrome decorated tiles from the interior of two churches (16th–17th century) and from the outdoor of a Palace (18th century). Small tile fragments were directly irradiated in a wavelength-dispersive X-ray fluorescence spectrometer for glaze chemical characterization and subsequently irradiated in a powder diffractometer to assess the phase constitution of both glaze and ceramic body.Cleaning and conserving these ancient cultural artifacts involve a decontamination process applying innovative non-destructive techniques. The present work is intended as a contribution to diagnose the actual degradation state of ancient tiles in view of future decontamination actions using gamma radiation.

Innovative non-destructive evaluation and damage characterisation of composite aerostructures using thermography

The present study is concerned with the reliability and effectiveness of innovative non-destructive techniques for damage characterisation and evaluation of aerospace materials and structures. Infrared thermography (IrT) was used with the aim of assessing the integrity of bonded repair on aluminium substrates. For this purpose, artificial damage of various dimensions was introduced in composite laminates. These defects were successfully monitored with IrT using different imaging techniques. IrT was also employed for the online monitoring of the loaded structure. The real time evolution of progressive debonding owing to fatigue loading was monitored. No external thermal stimulation was necessary as the cyclic loading provided thermal excitation on the system. The experimental results provided evidence that the innovative technique was capable of qualitatively and quantitatively assessing the integrity of patched repairs. In other words, this technique can be efficiently employed for damage identification and quantification.

Seasonal chemical–physical changes of PGI Pachino cherry tomatoes detected by magnetic resonance imaging (MRI)

Magnetic resonance imaging (MRI) has been used to study the variations of internal structure and chemical–physical characteristics of cherry tomatoes ( Lycopersicon esculentum cv. Shiren), one the most economically valuable horticultural crops, in different harvesting seasons. In particular, the study focused on PGI (Protected Geographical Indication) Pachino cherry tomatoes, characterised by taste and nutritional value, notably in the winter production, amounting about 500 ton/year. Spin–spin and spin–lattice relaxation times, T 2 and T 1 respectively, determined on whole fruit, provided useful data highlighting variations among samples according to the season (winter, spring and summer). MRI images evidenced differences among cellular tissues such as pericarp and endocarp, through variations of: (1) T 2 and T 1 measures and water tumbling and diffusion motion, (2) thicknesses of different morphological zones, (3) qualitative characteristics of the tissue covering placental cavities where seeds are contained. Results of variance analysis (ANOVA) showed that physical parameters, as the transverse and longitudinal relaxation times, T 2 and T 1, measured in the morphological tissues of vegetables are excellent variables highlighting their differences in different seasons. This innovative non-destructive technique in food science has great potential in fruit quality assessment.

Analysis of Load Transfer Behaviour and Determination of Interfacial Shear Strength in Single-Fibre-Reinforced Titanium Alloys

The effect of interfaces on load sharing behaviour has been evaluated by performing single-fibre fragmentation (SFF) experiments and analysis of titanium matrix composites at ambient and elevated temperatures. Fibre breaks were monitored by acoustic emission sensors, and the break locations were determined in-situ by an innovative ultrasonic non-destructive evaluation technique. Data analysis of SFF testing was performed using the Kelly-Tyson model. The length of fibre fragments and distribution were determined using innovative nondestructive technique. This study demonstrates that composite processing conditions can significantly affect the nature of the fibre/matrix interface and the resulting fragmentation behaviour of the fibre. Further, thermal micro-residual stresses, generated during the fabrication process and in-service due to the difference in thermomechanical characteristics of the model composite's constituents, play a major role influencing the interfacial shear stress transfer behaviour in single-fibre titanium matrix composites.

Determination of the refractive index of a lens using the Murty shearing interferometer

An innovative nondestructive technique for measuring the refractive index of a simple lens is described. The proposed method is superior to existing ones because the focusing error and the spherical aberrations are reduced. Apart from this, the strength parameters (i.e., r1 and r2) of a lens are not required at all since the derived lens-index formula is independent of the lens's physical parameters. The shearing interferometric technique is a sensitive aid for detecting the focal plane of the test lens. A modified criterion for determining the focal length has been used. In this case two miscible liquids or compounds are not necessary. The well-known liquid immersion method is the particular case of this technique. The Murty shearing interferometer has been used as an optical device to observe the defocusing defect in the form of fringes. The amount of defocusing is easily calculated. An equation for this error has been theoretically deduced and experimentally verified. The technique described is quick to perform and easy in handling. The various effects due to the lens's aperture and aberrations, thickness of the glass cell, liquid column, etc. are also discussed. For N liquids, there are N(N - 1)/2 ways of calculating the lens's index. Owing to its nature this is termed the nondestructive nonmiscible-liquid immersion technique for index measurement of a lens.