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Application of Ultrasonic Non-destructive Testing

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

Deadline for manuscript submissions: closed (20 February 2025) | Viewed by 16023

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Dr. Mário João S. F. Santos

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Guest Editor

Department of Electrical and Computer Engineering, University of Coimbra, 3030-290 Coimbra, Portugal
Interests: ultrasonic non-destructive characterization of materials; ultrasonic guided waves; composite inspection; biologic tissue characterization by ultrasounds
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Special Issue Information

Dear Colleagues,

This Special Issue is intended for the presentation of new ideas and experimental results related to applications of ultrasound non-destructive testing (UNDT). Ultrasound is an important technique in NDT, being largely used in industry. Metal and composite materials used in critical applications, such as aerospace structures, require appropriate NDT to guarantee safety. Thus, contributions on the latest R&D achievements on ‘Ultrasonic Non-Destructive Testing’, methodologies of testing, and evaluation, as well as on the development of new equipment, analyses, and approaches to non-destructive measurements are welcome.

Authors are encouraged to submit contributions in any of the following or related areas for UNDT:

Ultrasonic non-destructive testing/ultrasonic non-destructive evaluation;
Ultrasonic-based structural health monitoring and damage detection;
Material characterization;
NDT of composites;
Ultrasound phased arrays;
Guided waves;
Process monitoring;
Ultrasound sensors, transducers, and sensor networks;
Instruments, devices, and systems for ultrasound research and applications;
Ultrasound in civil, aerospace, and geological materials.

Dr. Mário João S. F. Santos
Guest Editor

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Keywords

ultrasound in civil, aerospace, and geological materials
ultrasonic NDT
ultrasonic NDE
ultrasonic-based SHM
material characterization
ultrasound phased arrays
guided waves
ultrasound transducers

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Published Papers (11 papers)

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Research

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28 pages, 12079 KiB

Open AccessArticle

Ultrasound Reconstruction Tomography Using Neural Networks Trained with Simulated Data: A Case of Theoretical Gradient Damage in Concrete

by Carles Gallardo-Llopis, Jorge Gosálbez, Sergio Morell-Monzó, Santiago Vázquez, Alba Font and Jordi Payá

Appl. Sci. 2025, 15(8), 4273; https://doi.org/10.3390/app15084273 - 12 Apr 2025

Viewed by 323

Abstract

Gradient damage processes in cementitious materials are generally produced by chemical and/or physical processes that travel from outside to inside. Depending on the type of damage, it can cause different effects such as decreased porosity, cracking, or steel corrosion in the case of carbonation, or increased porosity, micro-cracks, expansion, and spalling (also present in thermal damage) in the case of external attack by sulphates or acid attack. Therefore, estimating the boundaries of this damage is an essential task for concrete quality assessment. The first objective of this work was to use neural networks (NNs) for ultrasound tomographic reconstruction of concrete samples in order to estimate the advance front in gradient damage. Unlike the usual X-ray tomography, ultrasound tomography is affected by diffraction, among other factors. NNs can learn to compensate for these effects; however, they require a large amount of training data to achieve accurate results. In the case of cement-based materials, obtaining and measuring a real training database could be complicated, expensive, and time-consuming. For this purpose, a training process using simulated measurements was carried out. The second objective of this work was to demonstrate the feasibility of training neural networks through simulations, which reduces costs. Finally, the trained neural network for tomographic reconstruction was evaluated using real cylindrical concrete specimens. Each specimen consisted of an outer cylinder, representing externally exposed cement, and an inner cylinder, simulating the unaffected core. The Structural Similarity Index (SSIM) was used as a metric to assess the reconstruction accuracy, achieving values of 0.95 for simulated signals and up to 0.82 for real signals. Full article

(This article belongs to the Special Issue Application of Ultrasonic Non-destructive Testing)

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11 pages, 1240 KiB

Open AccessArticle

Calibration of a Quartz Tuning Fork as a Sound Detector

by Judith Falkhofen and Marcus Wolff

Appl. Sci. 2025, 15(7), 3655; https://doi.org/10.3390/app15073655 - 26 Mar 2025

Viewed by 165

Abstract

This study compares the performance of a quartz tuning fork (QTF) with a highly sensitive ultrasound microphone in the context of acoustic measurements, applying the substitution calibration method. QTF sensors are increasingly used for high-precision tasks due to their sensitivity and stability, while microphones are still the standard in general acoustic measurements. The aim of this study is to evaluate both technologies across several key performance metrics, including linearity of response, sensitivity, noise characteristics, and acoustic detection limit. Which sensor is better suited to which acoustic and physical condition? The results show that QTFs perform exceptionally well in applications requiring high precision, especially in high-frequency and narrow-band measurements. The signal-to-noise-ratio (SNR) of the QTF at its resonance frequency is 14 dB higher than that of the microphone, whereas the detection limit and linearity are comparable. The findings suggest that QTF sensors are particularly advantageous for specialized applications like photoacoustic spectroscopy (PAS). Full article

(This article belongs to the Special Issue Application of Ultrasonic Non-destructive Testing)

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15 pages, 1801 KiB

Open AccessArticle

Numerical Evaluation of Ultrasonic Detection of Solid Occlusions in CSP Molten Salt Piping

by Raffaele Dragonetti, Rosario Aniello Romano and Elio Di Giulio

Appl. Sci. 2025, 15(3), 1373; https://doi.org/10.3390/app15031373 - 29 Jan 2025

Viewed by 660

Abstract

This work presents a numerical evaluation of the applicability of non-invasive ultrasonic techniques for detecting solid inclusions in concentrated solar power (CSP) systems using molten salts. Under stagnant conditions, molten salts, such as the NaNO₃–KNO₃ mixture, solidify when the temperature drops below approximately 240 °C at ambient pressure. The study was conducted using finite element method (FEM) simulations in the time domain to model ultrasonic wave propagation and interaction with the solidified inclusions. Numerical analyses revealed that the energy of ultrasonic signals transmitted from the source and captured by the receiver can be used to quantify the energy reflected and scattered by solid inclusions and to statistically determine their spatial distribution within the piping. The study highlights the potential of detecting solid occlusions through statistical analysis of ultrasonic signals. Such an approach would enable decision making for trigger heating strategies to re-melt the solidified inclusions by raising the system’s temperature. This approach contrasts with traditional temperature-based control, which fails to quantify the degree of solidification and may result in frequent, energy-intensive heating whenever the temperature drops below the threshold. The proposed ultrasonic-based detection method thus offers a more energy-efficient and precise solution for managing solidification in CSP molten salt piping. Full article

(This article belongs to the Special Issue Application of Ultrasonic Non-destructive Testing)

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22 pages, 5527 KiB

Open AccessArticle

Ultrasonic Non-Destructive Testing of Accelerated Carbonation Cured-Eco-Bricks

by Joy Ayankop Oke and Hossam Abuel-Naga

Appl. Sci. 2024, 14(19), 8954; https://doi.org/10.3390/app14198954 - 4 Oct 2024

Viewed by 1041

Abstract

This study aimed to investigate the behavior of accelerated carbonation-cured laboratory specimens using the ultrasonic non-destructive testing (UNDT) method and compare the results with the destructive testing (DT) method. The materials used in the study included a blend of lime kiln dust and ground granulated blast furnace slag (LKD-GBFS) wastes, natural fine aggregate (sand), and alternative fine aggregates from waste tires. The chemical analysis of the LKD and GBFS samples highlighted them as suitable alternatives to OPC, hence their utilization in the study. A 60:40 (LKD-GBFS) blending ratio and a 1:2 mix design (one part LKD-GBFS blend and two part sand) was considered. The natural fine aggregate was partially replaced with fine waste tire rubber crumbs (TRCs) in stepped increments of 0, 5, and 10% by the volume of the sand. The samples produced were cured using three curing regimens: humid curing (HC), accelerated carbonation curing (ACC) with no water curing (NWC) afterwards, and water curing after carbonation (WC). From the results, an exponential model was developed, which showed a direct correlation between the UNDT and DT results. The developed model is a useful tool that can predict the CS of carbonated samples when cast samples are unavailable. Lastly, a total CO₂ uptake of 15,912 g (15.9 kg) was recorded, which underscores ACC as a promising curing technique that can be utilized in the construction industry. This technique will bring about savings in terms of the time required to produce masonry units while promoting a change in the basic assumptions of a safer and cleaner environment. Full article

(This article belongs to the Special Issue Application of Ultrasonic Non-destructive Testing)

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19 pages, 5069 KiB

Open AccessArticle

Delamination Localization in Multilayered CFRP Panel Based on Reconstruction of Guided Wave Modes

by Mastan Raja Papanaboina, Elena Jasiuniene, Vykintas Samaitis, Liudas Mažeika and Paulius Griškevičius

Appl. Sci. 2023, 13(17), 9687; https://doi.org/10.3390/app13179687 - 27 Aug 2023

Cited by 5 | Viewed by 1480

Abstract

Multi-layered composite materials are being used in various engineering fields, such as aerospace, automobile, and wind energy, because of their superior material properties. Due to various impact loads during the service life of composite structures, different types of defects can occur, such as matrix cracking, fiber breakage, delaminations, etc. In this research, a novel SHM technique for delamination detection and localization using a minimum number of sensors is proposed. The analytical, numerical, and experimental analysis of GW was performed to increase the probability of detection and localization of delaminations in CFRP material. A new analytical model was developed, which enables identifying converted and transmitted modes in the presence of multiple GW modes. A 2D FFT-based spatial filtering was used to filter the GW modes. The dominant A₀ mode was separated to inspect the delamination. Phase velocity is one of the important features in GW inspection to localize the delamination. A phase spectrum approach was developed to reconstruct the phase velocity dispersion of the GW modes in case material properties are unknown. Full article

(This article belongs to the Special Issue Application of Ultrasonic Non-destructive Testing)

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14 pages, 1095 KiB

Open AccessArticle

Characterizing the As-Fabricated State of Additively Fabricated IN718 Using Ultrasonic Nondestructive Evaluation

by Zebadiah Miles, Beytullah Aydogan, Guillermo Huanes-Alvan, Himanshu Sahasrabudhe and Sunil Kishore Chakrapani

Appl. Sci. 2023, 13(14), 8137; https://doi.org/10.3390/app13148137 - 13 Jul 2023

Cited by 4 | Viewed by 1662

Abstract

This article reports on the characterization of the “as-fabricated” state of Inconel 718 samples fabricated using laser directed energy deposition (DED). Laser-DED is known to produce complex metastable microstructures that can significantly influence the baseline ultrasonic response compared to conventional processing methods. The present work uses three parameters to characterize the samples: (a) ultrasonic velocity, (b) an attenuation coefficient, and (c) a backscatter coefficient. The baseline ultrasonic response from the DED sample was compared against the ultrasonic properties of conventional IN718 samples reported in the literature. The results suggest that strong grain boundary scattering from large macrograins can lead to attenuation and backscatter values that are significantly higher than conventional samples. Additionally, the results including velocities, attenuation and backscatter coefficients were found to be dependent on the fabrication direction, with the build direction being different from the transverse directions. Finally, destructive analysis was used to develop conjectures to explain the experimentally observed ultrasonic response. Full article

(This article belongs to the Special Issue Application of Ultrasonic Non-destructive Testing)

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15 pages, 41221 KiB

Open AccessArticle

Adhesive Single-Lap Joint Evaluation Using Ultrasound Guided Waves

by Mário Santos and Jaime Santos

Appl. Sci. 2023, 13(11), 6523; https://doi.org/10.3390/app13116523 - 26 May 2023

Cited by 5 | Viewed by 1544

Abstract

This work deals with the evaluation of adhesive single-lap joints using ultrasound guided waves; in particular, it is intended to characterize the signal propagation when defects are present in the adhesive joint by simulation and experimental approaches. The propagation of guided waves in the joint is developed from matrix formulations. The behavior of the guided wave modes that exist in the bonded region is characterized. It is found that its amplitudes can be estimated from the properties of the incoming wave that propagates in the non-bonded region. It is verified that the excitation of these modes is related to the degree to which the shapes of both modes match each other. A 3D simulation of two aluminum-bonded plates using 500 kHz ultrasonic transducers in a pitch-and-catch configuration was implemented using the Matlab k-Wave toolbox. Scattering effects, due to some defects located in the bond line of the joints, were simulated. The experimental setup with some artificial defects produced in the aluminum joints was used in order to compare it with the simulation. Qualitative agreement was observed between the two approaches. The observed deviation can be due to the different characteristics of the experimental and simulated defects. Full article

(This article belongs to the Special Issue Application of Ultrasonic Non-destructive Testing)

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19 pages, 5345 KiB

Open AccessArticle

Measurement of Air Layer Thickness under Multi-Angle Incidence Conditions Based on Ultrasonic Resonance Reflection Theory for Flange Fasteners

by Fei Shang, Bo Sun and Honghui Zhang

Appl. Sci. 2023, 13(10), 6057; https://doi.org/10.3390/app13106057 - 15 May 2023

Cited by 4 | Viewed by 1764

Abstract

During the servicing of flange fasteners, the sealing gasket and the flange cover interface are prone to separation and air contamination due to factors such as stress, corrosion, and vibration. In the detection process, there are two main issues: firstly, the conventional ultrasonic measurement methods based on the theory of acoustic elasticity are not applicable due to the small thickness of the air layer; secondly, the use of conventional vertical incidence detection methods is difficult to ensure due to the influence of the actual structure. To address these issues, this paper first establishes a mathematical model of ultrasonic resonance reflection, and then calculates the corresponding relationship between the air layer thickness and the resonance frequency under vertical incidence conditions. However, this model is difficult to use to calculate the resonance frequency under different incidence angles. To meet the requirements of different working conditions, a finite element simulation model is further established. By comparing the calculation results of the two models under vertical incidence, the reliability of the established finite element model is verified. The reflection and transmission pressure acoustic field distribution under different incidence angles and air layer thicknesses is simulated, and the function relationship between the incidence angle, air layer thickness, and the corresponding first-order resonance frequency is derived. This enables the measurement of the air layer thickness at any incidence angle, providing technical and theoretical support for practical industrial applications. Full article

(This article belongs to the Special Issue Application of Ultrasonic Non-destructive Testing)

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10 pages, 808 KiB

Open AccessCommunication

Numerical Study of Mode Conversion between Fundamental Lamb and Rayleigh Waves

by Alex Vu, Leonard J. Bond and Sunil K. Chakrapani

Appl. Sci. 2023, 13(9), 5613; https://doi.org/10.3390/app13095613 - 1 May 2023

Cited by 4 | Viewed by 2122

Abstract

This article reports the findings of a numerical study of mode conversion between fundamental Lamb and Rayleigh waves and vice versa in quarter and half spaces. Fundamental Lamb wave (

A_{0}

and

S_{0}

) propagation in a plate attached to a [...] Read more.

This article reports the findings of a numerical study of mode conversion between fundamental Lamb and Rayleigh waves and vice versa in quarter and half spaces. Fundamental Lamb wave (

A_{0}

and

S_{0}

) propagation in a plate attached to a quarter space and the subsequent mode conversion to a Rayleigh wave was studied using finite element analysis. B-Scans show that a beat-like phenomenon can be observed for the R → L conversion and a generation length can be observed for the L → R conversion. The quarter-space model was also used to study the Rayleigh to Lamb mode conversion. Two hypotheses were developed based on the observed mode conversion efficiencies: (a) the main driving factor of mode conversion between Lamb and Rayleigh waves is the grazing incidence of bulk modes and (b) due to scattering and diffraction, the modes will require a generation length to stabilize in amplitude. Both hypotheses were tested and confirmed using numerical models, including a half-space model to study the diffraction of bulk waves from an incident Lamb wave. The results are of significance for nondestructive evaluation of complex structures where such structural discontinuities exist and it becomes important to understand the fundamental mode conversion phenomenon. Full article

(This article belongs to the Special Issue Application of Ultrasonic Non-destructive Testing)

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14 pages, 6033 KiB

Open AccessArticle

An Interface Pressure Detection Method of Cable Silicone Rubber-XLPE Based on Nonlinear Ultrasound

by Chunhua Fang, Jianben Liu, Aoqi Sun, Junxiong Wu, Rong Xia, Benhong Ouyang, Yilin Zhang and Fang Li

Appl. Sci. 2023, 13(9), 5404; https://doi.org/10.3390/app13095404 - 26 Apr 2023

Cited by 2 | Viewed by 1686

Abstract

The interface pressure between the cable attachment and the body is crucial for the stable long-term operation of the cable. To solve the issue of interface insulation characteristics’ damage caused by the pressure transducer measurement method, a non-destructive testing method of silicone rubber interface pressure using nonlinear ultrasound is presented. Initially, the study analyzes the propagation characteristics of ultrasonic waves at the interface of cross-linked polyethylene and silicone rubber. The study also establishes the relationship between the nonlinear coefficient and the interface pressure. Subsequently, a nonlinear ultrasonic test platform is constructed using the pulse reflection method to measure the interface pressure of flat silicone rubber and cross-linked polyethylene through nonlinear ultrasonic testing. Theoretical and experimental results indicate that the fundamental amplitude of the frequency domain of the interface reflection wave decreases, and the second harmonic amplitude and nonlinear coefficient both increase as pressure increases. These results demonstrate that the nonlinear ultrasound, non-destructive testing method can accurately evaluate the interfacial pressure state of the cable accessories. Full article

(This article belongs to the Special Issue Application of Ultrasonic Non-destructive Testing)

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Review

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24 pages, 8214 KiB

Open AccessReview

Recent Advancements in Guided Ultrasonic Waves for Structural Health Monitoring of Composite Structures

by Mohad Tanveer, Muhammad Umar Elahi, Jaehyun Jung, Muhammad Muzammil Azad, Salman Khalid and Heung Soo Kim

Appl. Sci. 2024, 14(23), 11091; https://doi.org/10.3390/app142311091 - 28 Nov 2024

Cited by 4 | Viewed by 2060

Abstract

Structural health monitoring (SHM) is essential for ensuring the safety and longevity of laminated composite structures. Their favorable strength-to-weight ratio renders them ideal for the automotive, marine, and aerospace industries. Among various non-destructive testing (NDT) methods, ultrasonic techniques have emerged as robust tools for detecting and characterizing internal flaws in composites, including delaminations, matrix cracks, and fiber breakages. This review concentrates on recent developments in ultrasonic NDT techniques for the SHM of laminated composite structures, with a special focus on guided wave methods. We delve into the fundamental principles of ultrasonic testing in composites and review cutting-edge techniques such as phased array ultrasonics, laser ultrasonics, and nonlinear ultrasonic methods. The review also discusses emerging trends in data analysis, particularly the integration of machine learning and artificial intelligence for enhanced defect detection and characterization through guided waves. This review outlines the current and anticipated trends in ultrasonic NDT for SHM in composites, aiming to aid researchers and practitioners in developing more effective monitoring strategies for laminated composite structures. Full article

(This article belongs to the Special Issue Application of Ultrasonic Non-destructive Testing)

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