Editorial

4 pages, 179 KiB

Open AccessEditorial

Special Issue on Ultrasonic Modeling for Non-Destructive Testing

by Michel Darmon

Appl. Sci. 2024, 14(5), 2008; https://doi.org/10.3390/app14052008 - 29 Feb 2024

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This Special Issue of Applied Sciences focuses on advancing modeling methods for the ultrasonic Non-destructive Testing (NDT) of materials [...] Full article

(This article belongs to the Special Issue Ultrasonic Modelling for Non-destructive Testing)

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19 pages, 5879 KiB

Open AccessArticle

Feasibility of Conventional Non-Destructive Testing Methods in Detecting Embedded FRP Reinforcements

by Pranit Malla, Seyed Saman Khedmatgozar Dolati, Jesus D. Ortiz, Armin B. Mehrabi, Antonio Nanni and Kien Dinh

Appl. Sci. 2023, 13(7), 4399; https://doi.org/10.3390/app13074399 - 30 Mar 2023

Cited by 9 | Viewed by 1928

Abstract

Fiber-Reinforced Polymer (FRP) bars/strands are the most promising alternative to their steel counterparts for reinforcing concrete elements due to their resistance to corrosion, lighter weight, higher strength and better durability. However, very limited research has been conducted in relation to non-destructive testing (NDT) [...] Read more.

Fiber-Reinforced Polymer (FRP) bars/strands are the most promising alternative to their steel counterparts for reinforcing concrete elements due to their resistance to corrosion, lighter weight, higher strength and better durability. However, very limited research has been conducted in relation to non-destructive testing (NDT) methods that are applicable to damage detection in FRP bars or the detection of FRP reinforcements embedded in concrete. The ability to assess the condition of the relatively new and unique FRP reinforcements will increase the confidence of the construction industry in their use as a reliable substitute for steel reinforcements. This paper investigates the ability of two of the most commonly used NDT methods, Ground Penetrating Radar (GPR) and Phased Array Ultrasonic (PAU), in detecting FRP bars/strands embedded in concrete elements. GPR and PAU tests were performed on two slab specimens reinforced with GFRP (Glass-FRP) bars, the most commonly used FRP bar, with variations in their depth, size and configuration, and a slab specimen with different types of available FRP reinforcements. The results show that GPR devices can detect GFRP bars/strands and CFRP (Carbon-FRP) strands to some extent, and their detectability increases with the increase in their antenna center frequency. On the contrary, PAU is only capable of detecting GFRP and CFRP strands. The results of this paper also emphasize the need for further research and developments related to NDT applications to embedded FRP bars. Full article

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20 pages, 2567 KiB

Open AccessArticle

A Non-Destructive Method for Predicting Critical Load, Critical Thickness and Service Life for Corroded Spherical Shells under Uniform External Pressure Based on NDT Data

by Cheng Huijuan Liu and Giuseppe Lacidogna

Appl. Sci. 2023, 13(7), 4172; https://doi.org/10.3390/app13074172 - 24 Mar 2023

Cited by 2 | Viewed by 1036

Abstract

A pressurized spherical shell that is continuously corroded will likely buckle and lose its stability. There are many analytical and numerical methods to study this problem (critical load, critical thickness, and service life), but the friendliness (operability) in engineering test applications is still [...] Read more.

A pressurized spherical shell that is continuously corroded will likely buckle and lose its stability. There are many analytical and numerical methods to study this problem (critical load, critical thickness, and service life), but the friendliness (operability) in engineering test applications is still not ideal. Therefore, in this paper, we propose a new non-destructive method by combining the Southwell non-destructive procedure with the stable analysis method of corroded spherical thin shells. When used carefully, it can estimate the critical load (critical thickness) and service life of these thin shells. Furthermore, its procedure proved to be more practical than existing methods; it can be easily mastered, applied, and generalized in most engineering tests. When used properly, its accuracy is acceptable in the field of engineering estimations. In the context of the high demand for non-destructive analysis in industry, it may be of sufficient potential value to be used as a reference for existing estimating methods based on NDT data. Full article

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23 pages, 627 KiB

Open AccessArticle

Marchenko Green’s Function Retrieval in Layered Elastic Media from Two-Sided Reflection and Transmission Data

by Joost Van der Neut, Joeri Brackenhoff, Giovanni Angelo Meles, Evert Slob and Kees Wapenaar

Appl. Sci. 2022, 12(15), 7824; https://doi.org/10.3390/app12157824 - 04 Aug 2022

Cited by 1 | Viewed by 1098

Abstract

By solving a Marchenko equation, Green’s functions at an arbitrary (inner) depth level inside an unknown elastic layered medium can be retrieved from single-sided reflection data, which are collected at the top of the medium. To date, it has only been possible to [...] Read more.

By solving a Marchenko equation, Green’s functions at an arbitrary (inner) depth level inside an unknown elastic layered medium can be retrieved from single-sided reflection data, which are collected at the top of the medium. To date, it has only been possible to obtain an exact solution if the medium obeyed stringent monotonicity conditions and if all forward-scattered (non-converted and converted) transmissions between the acquisition level and the inner depth level were known a priori. We introduce an alternative Marchenko equation by revising the window operators that are applied in its derivation. We also introduce an auxiliary equation for transmission data, which are collected at the bottom of the medium, and a coupled equation, which is based on both reflection and transmission data. We show that the joint system of the Marchenko equation, the auxiliary equation and the coupled equation can be succesfully inverted when broadband reflection and transmission data are available. This results in a novel methodology for elastodynamic Green’s function retrieval from two-sided data. Apart from these data, our approach requires P- and S-wave transmission times between the inner depth level and the top of the medium, as well as two angle-dependent amplitude scaling factors, which can be estimated from the data by enforcing energy conservation. Full article

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17 pages, 4334 KiB

Open AccessArticle

Image Human Thorax Using Ultrasound Traveltime Tomography with Supervised Descent Method

by Tong Zhang, Rui Guo, Haolin Zhang, Hongyu Zhou, Yeyu Cao, Maokun Li, Fan Yang and Shenheng Xu

Appl. Sci. 2022, 12(13), 6763; https://doi.org/10.3390/app12136763 - 04 Jul 2022

Cited by 4 | Viewed by 1397

Abstract

The change of acoustic velocity in the human thorax reflects the functional status of the respiratory system. Imaging the thorax’s acoustic velocity distribution can be used to monitor the respiratory system. In this paper, the feasibility of imaging the human thorax using ultrasound [...] Read more.

The change of acoustic velocity in the human thorax reflects the functional status of the respiratory system. Imaging the thorax’s acoustic velocity distribution can be used to monitor the respiratory system. In this paper, the feasibility of imaging the human thorax using ultrasound traveltime tomography with a supervised descent method (SDM) is studied. The forward modeling is computed using the shortest path ray tracing (SPR) method. The training model is composed of homogeneous acoustic velocity background and a high-velocity rectangular block moving in the domain of interest (DoI). The average descent direction is learned from the training set. Numerical experiments are conducted to verify the method’s feasibility. Normal thorax model experiment proves that SDM traveltime tomography can efficiently reconstruct thorax acoustic velocity distribution. Numerical experiments based on synthetic thorax model of pleural effusion and pneumothorax show that SDM traveltime tomography has good generalization ability and can detect the change of acoustic velocity in human thorax. This method might be helpful for the diagnosis and evaluation of respiratory diseases. Full article

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19 pages, 9689 KiB

Open AccessArticle

An Efficient Semi-Analytical Scheme for Determining the Reflection of Lamb Waves in a Semi-Infinite Elastic Waveguide

by Robert C. Davey, Raphaël C. Assier and I. David Abrahams

Appl. Sci. 2022, 12(13), 6468; https://doi.org/10.3390/app12136468 - 25 Jun 2022

Cited by 1 | Viewed by 1124

Abstract

The classical problem of reflection of Lamb waves from a free edge perpendicular to the centre line of an elastodynamic plate is studied. It is known that Lamb wave expansions for the displacement and stress fields poorly represent the irregular behaviour near corners, [...] Read more.

The classical problem of reflection of Lamb waves from a free edge perpendicular to the centre line of an elastodynamic plate is studied. It is known that Lamb wave expansions for the displacement and stress fields poorly represent the irregular behaviour near corners, leading to the slow convergence of a series of such waves. The form of the irregularity for an elastodynamic corner is derived asymptotically, and a new solution method, which incorporates this corner behaviour analytically, is then implemented. Results are presented showing that this new approach represents the near-field and far-field behaviour very accurately, requiring very modest numbers of Lamb wave and corner modes. Further, it is revealed that the method can recover the trapped-mode phenomenon encountered in this configuration at the Lamé frequency and a specific Poisson’s ratio that we find to be approximately

0.224798

. Full article

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17 pages, 2723 KiB

Open AccessArticle

Implementing Data-Driven Approach for Modelling Ultrasonic Wave Propagation Using Spatio-Temporal Deep Learning (SDL)

by Thulsiram Gantala and Krishnan Balasubramaniam

Appl. Sci. 2022, 12(12), 5881; https://doi.org/10.3390/app12125881 - 09 Jun 2022

Cited by 2 | Viewed by 1556

Abstract

In this paper, we proposed a data-driven spatio-temporal deep learning (SDL) model, to simulate forward and reflected ultrasonic wave propagation in the 2D geometrical domain, by implementing the convolutional long short-term memory (ConvLSTM) algorithm. The SDL model learns underlying wave physics from the [...] Read more.

In this paper, we proposed a data-driven spatio-temporal deep learning (SDL) model, to simulate forward and reflected ultrasonic wave propagation in the 2D geometrical domain, by implementing the convolutional long short-term memory (ConvLSTM) algorithm. The SDL model learns underlying wave physics from the spatio-temporal datasets. Two different SDL models are trained, with the following time-domain finite element (FE) simulation datasets, by applying: (1) multi-point excitation sources inside the domain and (2) single-point excitation sources on the edge of the different geometrical domains. The proposed SDL models simulate ultrasonic wave dynamics, for the forward ultrasonic wave propagation in the different geometrical domains and reflected wave propagation phenomenon, from the geometrical boundaries such as curved, T-shaped, triangular, and rectangular domains, with varying frequencies and cycles. The SDL is a reliable model, which generates simulations faster than the conventional finite element solvers. Full article

(This article belongs to the Special Issue Ultrasonic Modelling for Non-destructive Testing)

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19 pages, 6862 KiB

Open AccessArticle

An Experimental and Theoretical Comparison of 3D Models for Ultrasonic Non-Destructive Testing of Cracks: Part I, Embedded Cracks

by Michel Darmon, Gwenael Toullelan and Vincent Dorval

Appl. Sci. 2022, 12(10), 5078; https://doi.org/10.3390/app12105078 - 18 May 2022

Cited by 3 | Viewed by 1718

Abstract

Ultrasonic Non-Destructive Testing (NDT) methods are broadly used for detection and characterization/imaging of cracks. Simulation is of great interest for designing such NDT methods. To model the ultrasonic 3D response of a crack, ultrasonic high frequency asymptotic (semi-analytical) models (such as the Physical [...] Read more.

Ultrasonic Non-Destructive Testing (NDT) methods are broadly used for detection and characterization/imaging of cracks. Simulation is of great interest for designing such NDT methods. To model the ultrasonic 3D response of a crack, ultrasonic high frequency asymptotic (semi-analytical) models (such as the Physical Theory of Diffraction—PTD) are known to provide accurate predictions for most classical NDT configurations, and 3D numerical models have also emerged more recently. The aim of this paper is to carry out for the first time an experimental and theoretical comparison of 3D models for ultrasonic NDT of embedded cracks in 3D configurations. Semi-analytical models and a hybrid 3D FEM strategy—combining high-order spectral Finite Elements Method (FEM) for flaw scattering and an asymptotic ray model for beam propagation—have been compared. Both numerical validations and comparisons between simulation and experiments prove the effectiveness of PTD in numerous configurations but validate and demonstrate the improvement provided by the 3D hybrid code, notably for small flaws compared to the wavelength and for shear waves. Full article

(This article belongs to the Special Issue Ultrasonic Modelling for Non-destructive Testing)

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13 pages, 2808 KiB

Open AccessArticle

Smart Patch for Structural Health Monitoring of Composite Repair

by Tianyi Feng and M. H. Ferri Aliabadi

Appl. Sci. 2022, 12(10), 4916; https://doi.org/10.3390/app12104916 - 12 May 2022

Cited by 6 | Viewed by 1941

Abstract

The bondline integrity of a repair patch to the parent composite laminate is considered the most important factor in the repair design. A smart repair patch is proposed here to allow for real-time ultrasonic guided wave monitoring of repaired composites. A diagnostic film [...] Read more.

The bondline integrity of a repair patch to the parent composite laminate is considered the most important factor in the repair design. A smart repair patch is proposed here to allow for real-time ultrasonic guided wave monitoring of repaired composites. A diagnostic film with lead zirconate titanate (PZT) transducers and inkjet-printed wires is embedded into the repair patch using a cut-out method. The electro-mechanical impedance (EMI) method is used to verify the integrity of the embedded PZT transducers. The performance of the smart repair patch is assessed on the external panel with artificial bondline delamination and surface-mounted artificial damage. The damage index correlation coefficient and delay-and-sum (DAS) algorithm are used for damage detection and localization. The results show that the developed repair patch can successfully detect and locate damages. Full article

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19 pages, 16433 KiB

Open AccessArticle

The Spec-Radiation Method for Layered Fluid Media

by Andreas Sebastian Schmelt and Jens Twiefel

Appl. Sci. 2022, 12(3), 1098; https://doi.org/10.3390/app12031098 - 21 Jan 2022

Viewed by 1054

Abstract

The real-time evaluation for non-destructive air-coupled ultrasonic testing of panel materials is a big task for several industries. To make these tests more and more accurate, efficient and reliable calculation methods from ultrasonic holography are essential. In the past, we presented the spec-radiation [...] Read more.

The real-time evaluation for non-destructive air-coupled ultrasonic testing of panel materials is a big task for several industries. To make these tests more and more accurate, efficient and reliable calculation methods from ultrasonic holography are essential. In the past, we presented the spec-radiation method as a fast and accurate method for such tasks. The spec-radiation method calculates the sound field utilizing data from a measurement plane at another parallel or tilted plane, especially the sound field at the surface of a panel. This can be used to detect flaws. There is a limitation of the current method: using the data on the panel surface limits the accuracy of the detected flaws. A big step forward could be expected if the sound field in the material were known. As a first step, we developed the spec-radiation method forward to consider multiple material layers. For now, we made the major assumption that all layers have fluid-like properties. Hence, transversal waves were neglected. This extension of the spec-radiation method was validated utilizing an experiment. We present that flaws in the panel material can be detected with higher accuracy at a similar speed compared to our former approach. Full article

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19 pages, 5617 KiB

Open AccessArticle

Numerical Investigation of Excitation of Various Lamb Waves Modes in Thin Plastic Films

by Rymantas Jonas Kazys, Justina Sestoke and Egidijus Zukauskas

Appl. Sci. 2022, 12(2), 849; https://doi.org/10.3390/app12020849 - 14 Jan 2022

Cited by 1 | Viewed by 1401

Abstract

Ultrasonic-guided waves are widely used for the non-destructive testing and material characterization of plates and thin films. In the case of thin plastic polyvinyl chloride (PVC), films up to 3.2 MHz with only two Lamb wave modes, antisymmetrical A₀ and symmetrical S [...] Read more.

Ultrasonic-guided waves are widely used for the non-destructive testing and material characterization of plates and thin films. In the case of thin plastic polyvinyl chloride (PVC), films up to 3.2 MHz with only two Lamb wave modes, antisymmetrical A₀ and symmetrical S₀, may propagate. At frequencies lower that 240 kHz, the velocity of the A₀ mode becomes slower than the ultrasonic velocity in air which makes excitation and reception of such mode complicated. For excitation of both modes, we propose instead a single air-coupled ultrasonic transducer to use linear air-coupled arrays, which can be electronically readjusted to optimally excite and receive the A₀ and S₀ guided wave modes. The objective of this article was the numerical investigation of feasibility to excite different types of ultrasonic-guided waves, such as S₀ and A₀ modes in thin plastic films with the same electronically readjusted linear phased array. Three-dimensional and two-dimensional simulations of A₀ and S₀ Lamb wave modes using a single ultrasonic transducer and a linear phased array were performed. The obtained results clearly demonstrate feasibility to excite efficiently different guided wave modes in thin plastic films with readjusted phased array. Full article

(This article belongs to the Special Issue Ultrasonic Modelling for Non-destructive Testing)

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14 pages, 6202 KiB

Open AccessArticle

Edge and Notch Detection in a Plate Using Time Reversal Process of Leaky Lamb Waves

by Jean-Christophe Vallée, Marie-Aude Ploix, François Baqué, Matthieu Cavaro and Jean-François Chaix

Appl. Sci. 2022, 12(1), 228; https://doi.org/10.3390/app12010228 - 27 Dec 2021

Cited by 2 | Viewed by 2272

Abstract

Leaky Lamb waves are proven effective to carry out nondestructive testing especially on parallel and immersed plates. To detect and localize defects in such a set, this work associates for the first time the topological energy method and leaky Lamb waves. This methodology [...] Read more.

Leaky Lamb waves are proven effective to carry out nondestructive testing especially on parallel and immersed plates. To detect and localize defects in such a set, this work associates for the first time the topological energy method and leaky Lamb waves. This methodology is applied in a single immersed plate to validate its application. Firstly, Lamb mode A1 is generated in the plate, and the reflected waves on the defect are measured. A first case is examined where the edge is considered as a defect to be localized. Then, measurements are taken on a plate where a notch is machined. The measurements are time reversed and reinjected in a finite-element simulation. The results are then correlated with the direct problem of the topological energy method that is also simulated. In both cases, the defects are precisely localized on the energy images. This work is the preliminary step to an application of the topological energy method to a set of two parallel and immersed plates where the research defect is located in the second plate. Full article

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18 pages, 1958 KiB

Open AccessFeature PaperArticle

Towards Explainable Augmented Intelligence (AI) for Crack Characterization

by Larissa Fradkin, Sevda Uskuplu Altinbasak and Michel Darmon

Appl. Sci. 2021, 11(22), 10867; https://doi.org/10.3390/app112210867 - 17 Nov 2021

Cited by 5 | Viewed by 1778 | Correction

Abstract

Crack characterization is one of the central tasks of NDT&E (the Non-destructive Testing and Evaluation) of industrial components and structures. These days data necessary for carrying out this task are often collected using ultrasonic phased arrays. Many ultrasonic phased array inspections are automated [...] Read more.

Crack characterization is one of the central tasks of NDT&E (the Non-destructive Testing and Evaluation) of industrial components and structures. These days data necessary for carrying out this task are often collected using ultrasonic phased arrays. Many ultrasonic phased array inspections are automated but interpretation of the data they produce is not. This paper offers an approach to designing an explainable AI (Augmented Intelligence) to meet this challenge. It describes a C code called AutoNDE, which comprises a signal-processing module based on a modified total focusing method that creates a sequence of two-dimensional images of an evaluated specimen; an image-processing module, which filters and enhances these images; and an explainable AI module—a decision tree, which selects images of possible cracks, groups those of them that appear to represent the same crack and produces for each group a possible inspection report for perusal by a human inspector. AutoNDE has been trained on 16 datasets collected in a laboratory by imaging steel specimens with large smooth planar notches, both embedded and surface-breaking. It has been tested on two other similar datasets. The paper presents results of this training and testing and describes in detail an approach to dealing with the main source of error in ultrasonic data—undulations in the specimens’ surfaces. Full article

(This article belongs to the Special Issue Ultrasonic Modelling for Non-destructive Testing)

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16 pages, 6734 KiB

Open AccessArticle

Numerical Simulation of Enhanced Photoacoustic Generation and Wavefront Shaping by a Distributed Laser Array

by Ruijie Hou, Bin Xu, Zhiying Xia, Yang Zhang, Weiping Liu, Christ Glorieux, John H. Marsh, Lianping Hou, Xuefeng Liu and Jichuan Xiong

Appl. Sci. 2021, 11(20), 9497; https://doi.org/10.3390/app11209497 - 13 Oct 2021

Cited by 1 | Viewed by 1819

Abstract

In photoacoustic imaging, the use of arrayed laser sources brings several advantages. Acoustic waves can be generated with flexible control of wavefronts, bringing functionality such as ultrasonic beam steering and focusing. The use of arrays reduces the optical intensity while increasing the strength [...] Read more.

In photoacoustic imaging, the use of arrayed laser sources brings several advantages. Acoustic waves can be generated with flexible control of wavefronts, bringing functionality such as ultrasonic beam steering and focusing. The use of arrays reduces the optical intensity while increasing the strength of the ultrasonic wave, bringing the advantages of improved signal-to-noise ratio (SNR) while avoiding laser-induced damage. In this paper, we report a numerical model for studying the generation and shaping of acoustic wavefronts with laser arrays. The propagation of mechanical waves, photoacoustically generated by thermal expansion, is simulated and discussed in detail. In addition, a partially delayed distributed array is studied both theoretically and quantitatively. The developed model for wavefront control through time-delayed laser pulses is shown to be highly suited for the optimization of laser array generation schemes. Full article

(This article belongs to the Special Issue Ultrasonic Modelling for Non-destructive Testing)

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22 pages, 6387 KiB

Open AccessFeature PaperArticle

3D Modelling of the Scattering of the Fundamental Anti-Symmetric Lamb Mode (A₀) Propagating within a Point-Impacted Transverse-Isotropic Composite Plate

by Dilbag Singh, Mourad Bentahar, Charfeddine Mechri and Rachid El Guerjouma

Appl. Sci. 2021, 11(16), 7276; https://doi.org/10.3390/app11167276 - 07 Aug 2021

Cited by 2 | Viewed by 1829

Abstract

The present paper deals with an effort to model impact damage in 3D-FE simulation. In this work, we studied the scattering behavior of an incident A₀ guided wave mode propagating towards an impacted damaged zone created within a quasi-isotropic composite plate. Besides, [...] Read more.

The present paper deals with an effort to model impact damage in 3D-FE simulation. In this work, we studied the scattering behavior of an incident A₀ guided wave mode propagating towards an impacted damaged zone created within a quasi-isotropic composite plate. Besides, barely visible impact damage of the desired energy was created and imaged using ultrasonic bulk waves in order to measure the size of the damage. The 3D-FE frequency domain model is then used to simulate the scattering of an incident guided wave at a frequency below an A₁ cut-off with a wavelength comparable to the size of the damaged zone. The damage inside the plate is modeled as a conical-shaped geometry with decayed elastic stiffness properties. The model was first validated by comparing the directivity of the scattered fields for the A₀ Lamb mode predicted numerically with the experimental measurements. The modeling of the impact zone with conical-shape geometry showed that the scattering directivity of the displacement field depends significantly on the size (depth and width) of the conical damage created during the point-impact of the composite with potential applications allowing the determination of the geometric characteristics of the impacted areas. Full article

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16 pages, 4680 KiB

Open AccessArticle

Noise Reduction in the Swept Sine Identification Procedure of Nonlinear Systems

by Pietro Burrascano and Matteo Ciuffetti

Appl. Sci. 2021, 11(16), 7273; https://doi.org/10.3390/app11167273 - 07 Aug 2021

Cited by 4 | Viewed by 1291

Abstract

The Hammerstein model identification technique based on swept sine excitation signals proved in numerous applications to be particularly effective for the definition of a model for nonlinear systems. In this paper we address the problem of the robustness of this model parameter estimation [...] Read more.

The Hammerstein model identification technique based on swept sine excitation signals proved in numerous applications to be particularly effective for the definition of a model for nonlinear systems. In this paper we address the problem of the robustness of this model parameter estimation procedure in the presence of noise in the measurement step. The relationship between the different functions that enter the identification procedure is analyzed to assess how the presence of additive noise affects model parameters estimation. This analysis allows us to propose an original technique to mitigate the effects of additive noise in order to improve the accuracy of model parameters estimation. The different aspects addressed in the paper and the technique for mitigating the effects of noise on the accuracy of parameter estimation are verified on both synthetic and experimental data acquired with an ultrasonic system. The results of both simulations and experiments on laboratory data confirm the correctness of the assumptions made and the effectiveness of the proposed mitigation methodology. Full article

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15 pages, 3562 KiB

Open AccessArticle

Simulation of Fluid Dynamics Monitoring Using Ultrasonic Measurements

by Masaru Nagaso, Joseph Moysan, Christian Lhuillier and Jean-Philippe Jeannot

Appl. Sci. 2021, 11(15), 7065; https://doi.org/10.3390/app11157065 - 30 Jul 2021

Cited by 1 | Viewed by 1725

Abstract

The simulation of the propagation of ultrasonic waves in a moving fluid will improve the efficiency of the ultrasonic flow monitoring and that of the in-service monitoring for various reactors in several industries. The most recent simulations are mostly limited to 3D representations [...] Read more.

The simulation of the propagation of ultrasonic waves in a moving fluid will improve the efficiency of the ultrasonic flow monitoring and that of the in-service monitoring for various reactors in several industries. The most recent simulations are mostly limited to 3D representations of the insonified volume but without really considering the temporal aspect of the flow. The advent of high-performance computing (HPC) now makes it possible to propose the first 4D simulations, with the representation of the inspected medium evolving over time. This work is based on a highly accurate double simulation. A first computational fluid dynamics (CFD) simulation, performed in previous work, described the fluid medium resulting from the mixing of hot jets in a cold opaque fluid. There have been many sensor developments over the years in this domain, as ultrasounds are the only method able to give information in an opaque medium. The correct design of these sensors, as well as the precise and confident analysis of their measurements, will progress with the development of the modeling of wave propagation in such a medium. An important parameter to consider is the flow temperature description, as a temperature gradient in the medium deflects the wave path and may sometimes cause its division. We develop a 4D wave propagation simulation in a very realistic, temporally fluctuating medium. A high-performance simulation is proposed in this work to include an ultrasonic source within the medium and to calculate the wave propagation between a transmitter and a receiver. The analysis of the wave variations shows that this through-transmission setup can track the jet mixing time variations. The steps needed to achieve these results are described using the spectral-element-based numerical tool SPECFEM3D. It is shown that the low-frequency fluctuation of the liquid metal flow can be observed using ultrasonic measurements. Full article

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19 pages, 4476 KiB

Open AccessArticle

Quantitative Inspection of Complex-Shaped Parts Based on Ice-Coupled Ultrasonic Full Waveform Inversion Technology

by Wenjin Xu, Maodan Yuan, Weiming Xuan, Xuanrong Ji and Yan Chen

Appl. Sci. 2021, 11(10), 4433; https://doi.org/10.3390/app11104433 - 13 May 2021

Cited by 5 | Viewed by 1805

Abstract

Ultrasonic methods have been extensively developed in nondestructive testing for various materials and components. However, accurately extracting quantitative information about defects still remains challenging, especially for complex structures. Although the immersion technique is commonly used for complex-shaped parts, the large mismatch of acoustic [...] Read more.

Ultrasonic methods have been extensively developed in nondestructive testing for various materials and components. However, accurately extracting quantitative information about defects still remains challenging, especially for complex structures. Although the immersion technique is commonly used for complex-shaped parts, the large mismatch of acoustic impedance between water and metal prevents effective ultrasonic transmission and leads to a low signal-to-noise ratio(SNR). In this paper, a quantitative imaging method is proposed for complex-shaped parts based on an ice-coupled full waveform inversion (FWI) method. Numerical experiments were carried out to quantitatively inspect the various defects in a turbine blade. Firstly, the k-space pseudospectral method was applied to simulate ice-coupled ultrasonic testing for the turbine blade. The recorded full wavefields were then applied for a frequency-domain FWI based on the Limited-memory Broyden–Fletcher–Goldfarb–Shanno (L-BFGS) method. With a carefully selected iterative number and frequency, a successive-frequency FWI can well detect half wavelength defects. Extended studies on an open notch with different orientations and multiple adjacent defects proved its capability to detect different types of defects. Finally, an uncertainty analysis was conducted with inaccurate initial velocity models with a relative error of ±2%, demonstrating its robustness even with a certain inaccuracy. This study demonstrates that the proposed method has a high potential to inspect complex-shaped structures with an excellent resolution. Full article

(This article belongs to the Special Issue Ultrasonic Modelling for Non-destructive Testing)

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15 pages, 4504 KiB

Open AccessFeature PaperArticle

Multichannel Real-Time Electronics Platform for the Estimation of the Error in Impact Localization with Different Piezoelectric Sensor Densities

by Lorenzo Capineri, Andrea Bulletti and Eugenio Marino Merlo

Appl. Sci. 2021, 11(9), 4027; https://doi.org/10.3390/app11094027 - 28 Apr 2021

Viewed by 1606

Abstract

The work presents a structural health monitoring (SHM) electronic system with real-time acquisition and processing for the determination of impact location in laminate. The novelty of this work is the quantitative evaluation of impact location errors using the Lamb wave guided mode S [...] Read more.

The work presents a structural health monitoring (SHM) electronic system with real-time acquisition and processing for the determination of impact location in laminate. The novelty of this work is the quantitative evaluation of impact location errors using the Lamb wave guided mode S₀, captured and processed in real-time by up to eight piezoelectric sensors. The differential time of arrival is used to minimize an error function for the position estimation. The impact energy is correlated to the amplitudes of the antisymmetric (A₀) mode and the electronic design is described to avoid saturation for signal acquisition. The same electronic system is designed to acquire symmetric (S₀) low level signals by adequate gain, bandwidth, and signal-to-noise ratio. Such signals propagate into a 1.4 mm thick aluminum laminate at the group velocity of 5150 m/s with frequency components above 270 kHz, and can be discriminated from the A₀ mode to calculate accurately the differential arrival time. The results show that the localization error stabilizes at a value comparable with the wavelength of the S₀ mode by increasing the number of sensors up to six, and then remains constant at up to eight sensors. This suggests that a compromise can be found between sensor density and localization error. Full article

(This article belongs to the Special Issue Ultrasonic Modelling for Non-destructive Testing)

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