Special Issue "Nondestructive Testing (NDT): Volume II"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Acoustics and Vibrations".

Deadline for manuscript submissions: 30 October 2020.

Special Issue Editor

Prof. Dr. Giuseppe Lacidogna
Website SciProfiles
Guest Editor
Department of Structural,Geotechnical and Building Engineering (DISEG), Politecnico di Torino, Torino, Italy
Interests: damage analysis in structures and materials (concrete, masonry, and rocks); nondestructive testing (NDT); acoustic emission; electromagnetic emission; critical phenomena in structural mechanics; critical phenomena in geophysics; fracture mechanics; static and dynamic analysis of high-rise buildings
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Special Issue Information

Dear Colleagues, 

Following the great success of the Special Issue “Nondestructive Testing (NDT)”, which was closed in February 2020, we have decided to launch a second edition, which will hopefully be as successful and provide as much insight as the first.

The efficient maintenance of civil structures and infrastructures is becoming a major issue for public and private institutions due to the unavoidable aging and deterioration of materials. As a matter of fact, the structural conditions of built heritage affect both safety and economic aspects. In this context, structural health monitoring (SHM) is emerging as a crucial research field, able to provide vital information regarding the damage levels of structures and materials. In particular, by exploiting the most advanced technologies and techniques, nondestructive testing (NDT) is the ideal candidate in detecting defects and structural issues, both at the laboratory and full-scale levels, in a non-invasive way. Among others, acoustic emission, vibration-based identification methods, digital image correlation, tomography techniques, sonic–ultrasonic tests, Raman and terahertz spectroscopy, electromagnetic analysis, etc. allow evaluating the state of damage and its evolution during time.

Therefore, the aim of this new Special Issue is to reunite researchers working in the field of NDT-SHM, both at the material and structure scale. We expect this issue to provide novel insights on the application of NDT to a wide variety of materials (concrete, steel, masonry, composites, etc.) in the field of Civil Engineering and Architecture. Both experimental and numerical studies are welcome. 

Prof. Dr. Giuseppe Lacidogna
Guest Editor

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Keywords

  • Structural health monitoring
  • Nondestructive testing
  • Acoustic emission
  • Vibration-based identification methods
  • Digital image correlation
  • Tomography
  • Raman spectroscopy
  • Terahertz spectroscopy
  • Electromagnetic tests

Published Papers (11 papers)

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Research

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Open AccessArticle
The Spec-Radiation Method as a Fast Alternative to the Re-Radiation Method for the Detection of Flaws in Wooden Particleboards
Appl. Sci. 2020, 10(19), 6663; https://doi.org/10.3390/app10196663 - 23 Sep 2020
Abstract
For real-time evaluation of non-destructive air-coupled ultrasonic testing of wood-based materials, efficient and reliable calculation methods from ultrasonic holography are essential. Presented here is the spec-radiation method as a fast alternative to the re-radiation method. The spec-radiation method offers a more accurate and [...] Read more.
For real-time evaluation of non-destructive air-coupled ultrasonic testing of wood-based materials, efficient and reliable calculation methods from ultrasonic holography are essential. Presented here is the spec-radiation method as a fast alternative to the re-radiation method. The spec-radiation method offers a more accurate and up to 88% faster evaluation than the re-radiation method for the determination of flaws in particleboards. Flaws of sub-wavelength sizes can be identified and their shape and location can be determined with this method. The spec-radiation method produces a better reproduction of the sound field than the re-radiation method, especially in the area of the measuring plane. Full article
(This article belongs to the Special Issue Nondestructive Testing (NDT): Volume II)
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Open AccessArticle
Analysis of Local Damages Effect on Mechanical Responses of Underwater Shield Tunnel via Field Testing and Numerical Simulation
Appl. Sci. 2020, 10(18), 6575; https://doi.org/10.3390/app10186575 - 21 Sep 2020
Abstract
The investigation of concrete structural performance is crucial to maintain the stability of infrastructure. In order to assess structural stability, this work focuses on the development of an integrated framework to detect damaged conditions in the field and analyze their effect on mechanical [...] Read more.
The investigation of concrete structural performance is crucial to maintain the stability of infrastructure. In order to assess structural stability, this work focuses on the development of an integrated framework to detect damaged conditions in the field and analyze their effect on mechanical performance through nondestructive testing (NDT) technology and numerical models. First, a ground penetrating radar (GPR) and an infrared camera work collaboratively to identify the damaged positions of the concrete structure, with parameters calibrated by laboratory experiments. Then, a finite element model is established to study structural mechanical performance based on field conditions and detected results. In addition, the influenced regions induced by local damage are studied under different boundary conditions. As a case study, the devised method was employed in the Nanjing Yangtze River tunnel for stability assessment and disaster prevention. The detected results of the damaged conditions agree well with the actual conditions in the field. Numerical results show that the circumferential stress component is more significant than that observed longitudinally. The effect of local damage on stress implies a positive correlation with the rise of water pressure, in which the maximum stress response to the variation of water level is 45KPa per meter. Full article
(This article belongs to the Special Issue Nondestructive Testing (NDT): Volume II)
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Open AccessArticle
Electromagnetic Acoustic Detection of Steel Plate Defects Based on High-Energy Pulse Excitation
Appl. Sci. 2020, 10(16), 5534; https://doi.org/10.3390/app10165534 - 11 Aug 2020
Abstract
The conventional electromagnetic ultrasonic transducers (EMATs) rely on the static magnetic field created by magnets. The magnet increases the size of the EMATs, and the strong magnetic force of the magnet attracts the detected steel and even ferromagnetic particles. It can cause mechanical [...] Read more.
The conventional electromagnetic ultrasonic transducers (EMATs) rely on the static magnetic field created by magnets. The magnet increases the size of the EMATs, and the strong magnetic force of the magnet attracts the detected steel and even ferromagnetic particles. It can cause mechanical damage to the transducer and the detected objects. A new high-energy acoustic excitation system, without a static bias magnetic is designed, which does not include any magnets. As the core of the system, the high-energy pulse excitation power supplies a transient high voltage to the excitation coil by the LC oscillation circuit. The maximum amplitude of current can reach 1700 A, which is much larger than the current in the conventional EMATs. Compared with the conventional EMATs, the intensity of the ultrasonic signal is greatly strengthened and the size of the EMAT is effectively reduced. Therefore, it can detect high-temperature steel plates at a higher lift-off distance. In this paper, the transduction mechanism of high-energy pulse electromagnetic acoustic on ferromagnetic materials was studied, and the high-energy pulse excitation coil used for the A0 mode Lamb wave was designed. The interaction rule of the magnetic field, the force field, and the acoustic field, was obtained. Then, the EMAT lift-off characteristic experiment of the high-energy pulse excitation was carried out, and the defect detection experiment was conducted on a cracked steel plate. The results show that the A0 mode Lamb waves have caused a high signal-to-noise ratio and can accurately locate the crack, which has a great advantage in detecting the microcrack defects of ferromagnetic materials. Full article
(This article belongs to the Special Issue Nondestructive Testing (NDT): Volume II)
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Open AccessArticle
Nondestructive Evaluation of Solids Based on Deformation Wave Theory
Appl. Sci. 2020, 10(16), 5524; https://doi.org/10.3390/app10165524 - 10 Aug 2020
Abstract
The application of a recent field theory of deformation and fracture to nondestructive testing (NDT) is discussed. Based on the principle known as the symmetry of physical laws, the present field theory formulates all stages of deformation including the fracturing stage on the [...] Read more.
The application of a recent field theory of deformation and fracture to nondestructive testing (NDT) is discussed. Based on the principle known as the symmetry of physical laws, the present field theory formulates all stages of deformation including the fracturing stage on the same theoretical basis. The formalism derives wave equations that govern the spatiotemporal characteristics of the differential displacement field of solids under deformation. The evolution from the elastic to the plastic stage of deformation is characterized by a transition from longitudinal (compression) wave to decaying longitudinal/transverse wave characteristics. The evolution from the plastic to the fracturing stage is characterized by transition from continuous wave to solitary wave characteristics. Further, the evolution from the pre-fracturing to the final fracturing stage is characterized by transition from the traveling solitary wave to stationary solitary wave characteristics. In accordance with these transitions, the criterion for deformation stage is defined as specific spatiotemporal characteristics of the differential displacement field. The optical interferometric technique, known as Electronic Speckle-Pattern Interferometry (ESPI), is discussed as an experimental tool to visualize those wave characteristics and the associated deformation-stage criteria. The wave equations are numerically solved for the elastoplastic stages, and the resultant spatiotemporal behavior of the differential displacement field is compared with the experimental results obtained by ESPI. Agreement between the experimental and numerical results validates the present methodology at least for the elastoplastic stages. The solitary wave characteristics in the fracturing stages is discussed based on the experimental results and dislocation theory. Full article
(This article belongs to the Special Issue Nondestructive Testing (NDT): Volume II)
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Open AccessArticle
Digital Volume Correlation Applied to X-ray Micro-Tomography Images in Uniaxial Creep Tests on Anisotropic Clayey Rock
Appl. Sci. 2020, 10(14), 4898; https://doi.org/10.3390/app10144898 - 16 Jul 2020
Abstract
Creep tests are commonly performed to characterize time-dependent deformation of geological materials. Classical measuring methods are not suitable for long term tests and not able to provide full three-dimensional strain fields. In this study, Digital Volume Correlation (DVC) is applied to X-ray micro-tomography [...] Read more.
Creep tests are commonly performed to characterize time-dependent deformation of geological materials. Classical measuring methods are not suitable for long term tests and not able to provide full three-dimensional strain fields. In this study, Digital Volume Correlation (DVC) is applied to X-ray micro-tomography (XRMT) images from creep tests on a hard clayey rock. In situ uniaxial compression creep tests are performed under different levels of stress and with different loading orientations with respect to the structural anisotropy of rock. Based on the XRMT images taken during the creep tests, DVC is applied to compute the full three dimensional strain fields and global averages strains of tested samples. The effects of bedding planes and hard inclusions on the non-uniform distribution of strains are analyzed. Full article
(This article belongs to the Special Issue Nondestructive Testing (NDT): Volume II)
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Open AccessArticle
Research on the Scope of Spectral Width Parameter of Frequency Domain Methods in Random Fatigue
Appl. Sci. 2020, 10(14), 4715; https://doi.org/10.3390/app10144715 - 08 Jul 2020
Abstract
In the current fatigue life calculation theory, the most commonly used method is the frequency domain method. However, most of the frequency domain fatigue life prediction models do not indicate the scope of the application of the spectral width parameter. Different frequency domain [...] Read more.
In the current fatigue life calculation theory, the most commonly used method is the frequency domain method. However, most of the frequency domain fatigue life prediction models do not indicate the scope of the application of the spectral width parameter. Different frequency domain methods have strict applicability to the spectral width parameter, and improper model selection will lead significant error. Therefore, it is particularly important to determine the scope of application of the spectral width parameter for different frequency-domain methods. This paper firstly introduces the current frequency domain methods, then simulates the analogue spectrum and selects three materials for comparison in the different frequency-domain methods. By analyzing and comparing the results of random fatigue life and relative error results, the application of different frequency-domain methods is obtained, and random vibration simulation verification is carried out with the practical engineering example, which can provide a reference for the selection of life prediction models. Full article
(This article belongs to the Special Issue Nondestructive Testing (NDT): Volume II)
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Open AccessArticle
The Elastic Wave Propagation in Rectangular Waveguide Structure: Determination of Dispersion Curves and Their Application in Nondestructive Techniques
Appl. Sci. 2020, 10(12), 4401; https://doi.org/10.3390/app10124401 - 26 Jun 2020
Abstract
The use of mechanic waves for assessing structural integrity is a well-known non-destructive technique (NDT). The ultrasound applied in the guided wave in particular requires significant effort in order to understand the complexities of the propagation so as to develop new methods in [...] Read more.
The use of mechanic waves for assessing structural integrity is a well-known non-destructive technique (NDT). The ultrasound applied in the guided wave in particular requires significant effort in order to understand the complexities of the propagation so as to develop new methods in damage detection, in this case, knowing the interaction between the wave propagation and the geometry of the waveguides is mandatory. In the present work, the wave propagation in rectangular steel rod is presented. In this study, the section dimensions were fixed as 5 × 15 [mm], a typical element of the flexible riser structural amour commonly used in the offshore oil industry. The studies here presented were restricted to [0, 100 KHz] frequencies. This frequency interval is in the range of commercial waveguide equipment commonly applied in ducts in NDT applications. The computation of the dispersion curves is performed by using three different methodologies: (i) analytical solutions, (ii) a method that combines analytical approaches with finite element methods (SAFE), and (iii) experimental method that extracted information from the rod using laser vibrometers and piezoelectric actuators. Finally, two applications based on the dispersion curves determined in the rectangular waveguide are presented to illustrate the possibilities of the curve dispersion knowledge related to the specific geometry in the development and application linked to NDT. The first application consists on showing the possibilities of the techniques that use a fiber grating Bragg cell (FGB) to measure the wave displacement and the second application involves the simulation of pre-fissured prismatic waveguide aimed at searching to induce three characteristic acoustic events. The model was built combining the finite element method and a version of the discrete element method. Full article
(This article belongs to the Special Issue Nondestructive Testing (NDT): Volume II)
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Open AccessArticle
Electromagnetic Testing of Moisture Separation Reheater Tube based on Multivariate Singular Spectral Analysis
Appl. Sci. 2020, 10(11), 3954; https://doi.org/10.3390/app10113954 - 06 Jun 2020
Abstract
Moisture separator reheater (MSR) tubing systems are an important part of a pressurized-water power plant to increase the efficiency of the heat transfer rate. The MSR tubes are finned tubes which are made of ferritic stainless steel (SS439) with a high strength and [...] Read more.
Moisture separator reheater (MSR) tubing systems are an important part of a pressurized-water power plant to increase the efficiency of the heat transfer rate. The MSR tubes are finned tubes which are made of ferritic stainless steel (SS439) with a high strength and corrosion resistance characteristics. However, corrosion can appear along with the fins after a long period of operation of the MSR tubes that requires nondestructive testing (NDT) of the MSR tubes’ periodically. Electromagnetic testing (ET) is an efficient NDT method for the inspection of far-side corrosion in the MSR tubes. However, the ET sensor signal is affected by signal noise from the fins. Material degradation that make it challenging to inspect and evaluate the corrosion. In this study, we proposed three ET methods, including magnetic flux leakage testing, eddy current testing and partial saturation eddy current testing, and incorporated with a multivariate singular spectral analysis (MSSA) filter to improve the detectability of the corrosion in the MSR tubes. The proposed MSSA filter was compared with the multivariate wavelet transform filter and Gabor transform filter, and the results showed more efficient and stable results of the MSSA filter in the extraction of the corrosion signal. Full article
(This article belongs to the Special Issue Nondestructive Testing (NDT): Volume II)
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Open AccessArticle
Acoustic Emission Monitoring of the Turin Cathedral Bell Tower: Foreshock and Aftershock Discrimination
Appl. Sci. 2020, 10(11), 3931; https://doi.org/10.3390/app10113931 - 05 Jun 2020
Cited by 1
Abstract
Historical churches, tall ancient masonry buildings, and bell towers are structures subjected to high risks due to their age, elevation, and small base-area-to-height ratio. In this paper, the results of an innovative monitoring technique for structural integrity assessment applied to a historical bell [...] Read more.
Historical churches, tall ancient masonry buildings, and bell towers are structures subjected to high risks due to their age, elevation, and small base-area-to-height ratio. In this paper, the results of an innovative monitoring technique for structural integrity assessment applied to a historical bell tower are reported. The emblematic case study of the monitoring of the Turin Cathedral bell tower (northwest Italy) is herein presented. First of all, the damage evolution in a portion of the structure localized in the lower levels of the tall masonry building is described by the evaluation of the cumulative number of acoustic emissions (AEs) and by different parameters able to predict the time dependence of the damage development, in addition to the 3D localization of the AE sources. The b-value analysis shows a decreasing trend down to values compatible with the growth of localized micro and macro-cracks in the portion of the structure close to the base of the tower. These results seem to be in good agreement with the static and dynamic analysis performed numerically by an accurate FEM (finite element model). Similar results were also obtained during the application of the AE monitoring to the wooden frame sustaining the bells in the tower cell. Finally, a statistical analysis based on the average values of the b-value are carried out at the scale of the monument and at the seismic regional scale. In particular, according to recent studies, a comparison between the b-value obtained by AE signal analysis and the regional activity is proposed in order to correlate the AE detected on the structure to the seismic activity, discriminating foreshock, and aftershock intervals in the analyzed time series. Full article
(This article belongs to the Special Issue Nondestructive Testing (NDT): Volume II)
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Open AccessArticle
Identification of Deformation Stage and Crack Initiation in TC11 Alloys Using Acoustic Emission
Appl. Sci. 2020, 10(11), 3674; https://doi.org/10.3390/app10113674 - 26 May 2020
Abstract
The Acoustic Emission (AE) is a widely used real-time monitoring technique for the deformation damage and crack initiation of areo-engine blades. In this work, a tensile test for TC11 titanium alloy, one of the main materials of aero-engine, was performed. The AE signals [...] Read more.
The Acoustic Emission (AE) is a widely used real-time monitoring technique for the deformation damage and crack initiation of areo-engine blades. In this work, a tensile test for TC11 titanium alloy, one of the main materials of aero-engine, was performed. The AE signals from different stages of this test were collected. Then, the AE signals were decomposed by the Variational Mode Decomposition (VMD) method, in which the signals were divided into two different frequency bands. We calculated the engery ratio by dividing the two different frequency bands to characterize TC11′s degree of deformation. The results showed that when the energy ratio was −0.5 dB, four stages of deformation damage of the TC11 titanium alloy could be clearly identified. We further combined the calculated Partial Energy Ratio (PER) and Weighted Peak Frequency (WPF) to identify the crack initiation of the TC11 titanium alloy. The results showed that the identification accuracy was 96.33%. Full article
(This article belongs to the Special Issue Nondestructive Testing (NDT): Volume II)
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Review

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Open AccessReview
Terahertz Inspection of Buildings and Architectural Art
Appl. Sci. 2020, 10(15), 5166; https://doi.org/10.3390/app10155166 - 27 Jul 2020
Abstract
We present a broad literature review on the uses of terahertz radiation for the inspection architectural art, as well as building structures. As an example of the uses of terahertz in this field, we also include original results on a non-destructive assessment of [...] Read more.
We present a broad literature review on the uses of terahertz radiation for the inspection architectural art, as well as building structures. As an example of the uses of terahertz in this field, we also include original results on a non-destructive assessment of a conservation intervention on murals of the Konstantinbasilika in Trier, Germany while using terahertz time-of-flight spectroscopy. Full article
(This article belongs to the Special Issue Nondestructive Testing (NDT): Volume II)
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