Nondestructive Evaluation Of Materials Research Articles

A Theoretical Investigation of the Penetration Depth in Motion Induced Eddy Current Testing

Conventional eddy current testing is a well-established technique in the non-destructive evaluation of materials which is limited by the fact that due to the penetration depth only defects close to the surface of the component can be detected. In this paper the concept of motion induced eddy current testing is presented which makes use of the relative motion between a permanent magnet and the test object. The corresponding Lorentz force influences the motion of electrons and disturbances in the current flow due to defects can be measured. The results are penetration depths two orders of magnitude larger than those recorded for conventional eddy current testing. In this way even deep lying defects can be detected yielding a considerable improvement compared to conventional eddy current testing.

Enhanced detection of fine damage in composite materials using integrated X-ray computed tomography, digital volume correlation, and U-Net

Accurate detection of fine damage in composite materials is essential for advancing research and engineering practices in various industries. This study introduces a novel method for detecting fine damage by integrating Digital Volume Correlation (DVC) and U-Net. X-ray computed tomography (XCT) images are analyzed to correlate microstructural features with damage progression. DVC residuals highlight new damage, while U-Net enhances segmentation precision. This approach addresses challenges in differentiating inherent flaws from new cracks, improving detection accuracy. Experimental validation and synthetic data generated by the discrete element method (DEM) demonstrate the method's robustness. The results show that the method is susceptible to newly formed microcracks and can accurately identify fine cracks, with over 60% being nearly invisible in XCT images. Cyclic loading experiments on two mortar samples reveal that cracks are the predominant form of damage, exhibiting different evolution characteristics during the loading process. The method significantly advances the non-destructive damage evaluation of composite materials.

Possibility of determining high quantitative fecal occult blood on stool surface using hyperspectral imaging

BackgroundFecal immunochemical tests are commonly performed for colorectal cancer screening. Instant fecal occult blood measurement in toilet bowel movements would improve convenience. Hyperspectral imaging (HSI) enables the nondestructive evaluation of materials that are difficult to assess visually. This study aimed to determine whether HSI could be used to identify fecal occult blood on stool surfaces.MethodsThe study included 100 patients who underwent colonoscopy, divided into groups A and B (50 patients, each) for creating a discriminant algorithm and validating the accuracy of the algorithm, respectively. In group A, 100 areas were randomly selected from the stool surface, and the fecal occult blood quantitative values were measured and photographed using a hyperspectral camera (cutoff: > 400 ng/mL). A discriminant algorithm image was created to extract spectral feature differences obtained from HSI via machine learning. In group B, 250 random areas were evaluated and compared to fecal occult blood quantitative values, measuring sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV).ResultsGroups A and B comprised 28 and 26 patients with cancer, respectively. Cancer detection sensitivity at the 400 ng/mL cutoff was 67.9% and 42.3% in groups A and B, respectively. The discriminant algorithm image exhibited high accuracy in group A (sensitivity; 77.1%, specificity; 96.9%, accuracy; 90.0%, PPV; 93.1%, NPV; 88.7%). In group B, the sensitivity, specificity, accuracy, PPV, and NPV were 83.3, 92.9, 90.8, 76.3, and 95.3%, respectively.ConclusionHSI can effectively discriminate high quantitative fecal occult blood, highlighting its potential for improved colorectal cancer screening.

Application of photothermal beam deflection spectrometry for non-destructive evaluation of advanced materials: a state-of-the-art review

Abstract The progress made in lasers and data acquisition systems has paved the way for innovative non-destructive evaluation methods based on the photothermal phenomenon. Beam deflection spectrometry (BDS) is a photothermal spectroscopic technique that offers ultra-sensitivity, high signal-to-noise ratios, and reduced sample preparation requirements. These advantages provide precise assessment of advanced material (AM) properties. This review presents a comprehensive in-depth analysis, thus helping researchers to understand the potential and future perspectives of BDS along with the theory, instrumentation, and application supported by the literature data. The objective of this review is also to present the possibilities of BDS in the characterization of AMs, including organic, inorganic, and hybrid organic–inorganic materials in the form of thin films, coatings, composites, and nanomaterials.

A review of Electrical Resistivity Tomography (ERT) applications in non-destructive evaluation of construction materials

A review of Electrical Resistivity Tomography (ERT) applications in non-destructive evaluation of construction materials

Past, Present, and Future of New Applications in Utilization of Eddy Currents

Eddy currents are an electromagnetic phenomenon that represent an inexhaustible source of inspiration for technological innovations in the 21st century. Throughout history, these currents have been a subject of research and technological development in multiple fields. This article delves into the fascinating world of eddy currents, revealing their physical foundations and highlighting their impact on a wide range of applications, ranging from non-destructive evaluation of materials to levitation phenomena, as well as their influence on fields as diverse as medicine, the automotive industry, and aerospace. The nature of eddy currents has stimulated the imaginations of scientists and engineers, driving the creation of revolutionary technologies that are transforming our society. As we progress through this article, we will cover the main aspects of eddy currents, their practical applications, and challenges for future works.

Extreme fine-tuning and explainable AI model for non-destructive prediction of concrete compressive strength, the case of ConcreteXAI dataset

This groundbreaking study introduces a novel approach employing Extreme Fine-Tuning (XFT) combined with Explainable Artificial Intelligence (XAI) for the accurate, non destructive prediction of concrete compressive strength. By analyzing a state-of-the-art dataset containing 18,480 data points, this study developed a deep neural network that, through extensive hyperparameter optimization, achieves unprecedented prediction accuracy of approximately 98.7%. The novelty of this research lies in the sophisticated integration of XFT and XAI techniques, which not only significantly enhances prediction accuracy but also provides insightful explanations of the model’s decision-making process, shedding light on the factors influencing concrete strength. This dual focus on accuracy and explainability represents a significant advancement in the application of Artificial Intelligence (AI) in material science and civil engineering, offering a powerful tool for researchers and practitioners.This study culminates in a model that outperforms existing methodologies in predicting concrete compressive strength, with an accuracy superior to 98.5% in both instances, testing and validation. By integrating XAI into this approach, we have also opened new avenues for understanding the complex relationships between concrete composition and its mechanical properties. This study marks a substantial step forward in the non-destructive evaluation of construction materials. It sets a new benchmark for transparency and interpretability in AI models within the engineering domain.

Robust transport and topological valley refraction of fundamental symmetric lamb waves in perforated phononic crystal plates

Lamb waves can be divided into antisymmetric Lamb waves (type A) and symmetric Lamb waves (type S), which are widely used in health monitoring of engineering structures and nondestructive evaluation of materials. However, due to the fact that each mode of Lamb wave has the setting group velocity in a certain bandwidth range, it is easy to cause the aliasing of multi-mode Lamb waves, partly limiting the application scenarios of Lamb wave. In this paper, a hexagonal lattice meta-structure is designed and the zero-order symmetric (S0) Lamb wave in a finite thickness plate is successfully separated. By breaking the spatial C 3v symmetry, a valley topological phononic crystal (PnC) plate for the pure S0 mode is constructed, and its robust topological transports are demonstrated. Firstly, the valley topological phase transition of S0 mode is realized by changing the angle of scatterer in PnC plate and the valley edge state of S0 mode is obtained. Furthermore, by introducing structural mismatch, it is verified that the edge state of S0 mode is robust to various bends and defect. Finally, by changing the material property of the terminal, the valley refraction with different directionality is realized. The results offer a route to individually study the symmetric modes of Lamb waves, and have potential application prospects in rapid and accurate ultrasonic nondestructive testing based on Lamb waves.

Rapid one-shot dual-shearing digital shearography using a spatial light modulator.

Digital shearography is a non-contact, whole-field, and high-accuracy laser-based optical interferometric method. It is widely used in the field of non-destructive testing and material evaluation. Dual-shearing DS, as the state-of-the-art method, can detect defects or measure the derivative of deformation in two sensitive directions. Most existing dual-shearing DS is realized with a bulky Michelson or Mach-Zehnder interferometer; recently, the usage of a spatial light modulator (SLM) in DS offers a new approach to designing a simple and light shearographic system. However, prior proposed SLM-based DS requires multiple shots for the phase map acquisition, with the classic temporal phase-shift (TPS) technique severely limiting its applications. This paper proposes a novel, to our best knowledge, one-shot dual-shearing DS by creating a dual-stripe pattern in the SLM. Two separate phase maps, with different sensitive directions, were acquired simultaneously via the spatial phase-shift technique. The measurement can be easily done within a single shot in its compact and light body. Moreover, the shearing amount of the two sensitive directions can be set independently and precisely. These advantages promote that the proposed system can be applied in various applications, especially for dynamic and complicated composite material testing. A detailed theory and experimental validation are described.

Detection and evaluation of thermal aging brittleness of heat-resistant steel using magneto-acoustic compound techniques

ABSTRACT The service life and structural safety of components are affected by the thermal ageing of materials; therefore, a non-destructive evaluation of materials is extremely essential and crucial. In this work, heat-resistant steel Cr12MoV was selected as a specimen, and the embrittlement period of heat-resistant steel Cr12MoV was obtained by accelerated thermal ageing experiments. The effects of service temperature and service time on the mechanical properties of heat-resistant steel were analysed. The non-destructive testing of heat-resistant steel was carried out by using magneto-acoustic compound detection techniques based on electromagnetic acoustic transducers. In the process, magneto-acoustic compound detection signals were decoupled. The electromagnetic characteristic parameters and ultrasonic characteristic parameters of the detection signals were extracted to evaluate the mechanical properties and thermal ageing of heat-resistant steel. The quantitative evaluation ability of thermal ageing brittleness of heat-resistant steel was improved by using the magneto-acoustic compound detection techniques compared with single eddy current detection method or single ultrasonic detection method.

Visualization of Micro Damage in SOFC Using Terahertz Waves

SOFC effective area for power generation is reduced when delamination occurs. Hence, non-destructive evaluation methods for detecting delamination of SOFC are required. We focused on Terahertz-Time Domain Spectroscopy (THz-TDS) as a SOFCs’ non-destructive evaluation method. THz-TDS has been used as an effective and safe method for non-destructive evaluation of non-metal materials. However, THz-TDS generates a huge amount of measurement data for one batch test. In this study, we propose a THz-TDS based method to visualize the internal damage of SOFC by using machine learning. Each waveform was discretely vectorized, and a Self -Organizing Map (SOM) was utilized to examine for its similarity. Therefore, we found that the waveforms have been changed because of the wave interference induced by the generation of air layer associated with the occurrence of delamination.

Enhanced damage imaging in three-dimensional composite structures via electrical impedance tomography with mixed and level set regularization

Electrical impedance tomography (EIT) is a promising tool for nondestructive evaluation (NDE) of materials that exhibit stimulus-responsive electrical conductivity. To date, materials practitioners of EIT have used standard regularization methods such as smoothness-promoting operators to solve the ill-posed EIT inverse problem. However, more sophisticated and better performing regularization methods exist. It is essential that these other regularization methods be explored in order for EIT to see more widespread adoption in NDE. To that end, we present two novel regularization techniques – a mixed smoothness/focal method and a level set method – for application to damage imaging via EIT. These new techniques are experimentally validated on two three-dimensional composite components, a carbon black-modified glass fiber/epoxy tube and a carbon fiber/epoxy laminate airfoil subject to multiple damaging impacts. It is shown that both of the new regularization techniques markedly outperform traditional smoothness-only methods. These results are an important step towards adoption of more sophisticated EIT formulations in NDE and transition of EIT from the proof-of-concept phase and into practice for engineered materials.

A magneto-mechanical model for the magnetic non-destructive evaluation of ferromagnetic materials

In this paper, a new magneto-mechanical constitutive model is established based on the macro-thermodynamic relationship, the micro-magnetic domain theory and Jiles–Atherton–Sablic (J–A–S) theory. The fitting expression of magnetostriction newly describes the nonlinear stress dependence, which is extended to six-order magnetization terms. In particular, the new expressions of nonlinear functions related to the maximum point of magnetostriction (MPM) are introduced into the magnetostriction expression. In addition, the improved expressions of the plastic stress equivalent field and the three parameters (i.e., the inter-domain coupling parameter, the field relaxation factor and the loss coefficient) considering the nonlinear stress dependence are introduced into the magnetization expressions. Compared to the various experimental results and the theoretical results by the existing models, it is clearly perceived that the new model has an excellent prediction ability of the magnetostrictive and magnetic behaviors in ferromagnetic materials under the elasto-plastic stress and magnetic field. Furthermore, the prediction accuracy of the magnetic parameters related to the magnetic non-destructive evaluation (MNDE) is greatly improved. The integrative analysis of the magnetostrictive and magnetic behaviors in various ferromagnetic materials demonstrates that the presented model can be widely used in the quantitative study of the MNDE as well as in the research of the magneto-mechanical behavior and the application of ferromagnetic materials.

Terahertz Spectroscopic Characterization and Thickness Evaluation of Internal Delamination Defects in GFRP Composites

The use of terahertz time-domain spectroscopy (THz-TDS) for the nondestructive testing and evaluation (NDT&E) of materials and structural systems has attracted significant attention over the past two decades due to its superior spatial resolution and capabilities of detecting and characterizing defects and structural damage in non-conducting materials. In this study, the THz-TDS system is used to detect, localize and evaluate hidden multi-delamination defects (i.e., a three-level multi-delamination system) in multilayered GFRP composite laminates. To obtain accurate results, a wavelet shrinkage de-noising algorithm is used to remove the noise from the measured time-of-flight (TOF) signals. The thickness and location of each delamination defect in the z-direction (i.e., through-the-thickness direction) are calculated from the de-noised TOF signals considering the interaction between the pulsed THz waves and the different interfaces in the GFRP composite laminates. A comparison between the actual and the measured thickness values of the delamination defects before and after the wavelet shrinkage denoising process indicates that the latter provides better results with less than 3.712% relative error, while the relative error of the non-de-noised signals reaches 16.388%. Also, the power and absorbance levels of the THz waves at every interface with different refractive indices in the GFRP composite laminates are evaluated based on analytical and experimental approaches. The present study provides an adequate theoretical analysis that could help NDT&E specialists to estimate the maximum thickness of GFRP composite materials and/or structures with different interfaces that can be evaluated by the THz-TDS. Also, the accuracy of the obtained results highlights the capabilities of the THz-TDS for the NDT&E of multilayered GFRP composite laminates.

A magnetoelectric-ultrasonic multimodal system for synchronous NDE of surface and internal defects in metal

In the field of non-destructive evaluation (NDE) of solid metal materials, it has been a challenge to detect surface and internal defects simultaneously by using a single physical mechanism technique. Conventionally, different testing techniques, in which each one is particularly sensitive to a certain type of defect, are employed to gain full defect information. However, a separated testing method is always a time-consuming and laborious work. Here, we report a magnetoelectric-ultrasonic hybrid transducer and multimodal system for quantitative NDE of metal, which integrates a magnetoelectric composite wrapped with a coil for generating alternating current field and simultaneously measuring magnetic abnormal of surface defects (referred to as ME-ACFM) and a dual-piezoceramic ultrasonic transducer (DP-UT) for generating acoustic pulses and detecting the echo signal of internal defects, respectively. A bipulse signal with different pulse widths is used for excitation of the hybrid transducer, in which one is corresponded to the resonant frequencies of 5 MHz for DP-UT, and another to 122 kHz for ME-ACFM. The huge difference between two resonant frequencies is helpful for restraining signal interference each other. Experimental investigations show that when scanning the tested specimens (standard steel No.45 and aluminum plates), the surface and internal defects information can be obtained simultaneously almost without a dead zone. The surface defect resolutions of 0.1 mm width and 0.1 mm depth, and the inside defect resolution of 2 mm blind hole are obtained; the experimental errors for surface defect (crack) depth up to 5 mm are around 5 %; while experimental errors for ultrasonic depth measurement (with a blind zone of 1.25 mm) is less than 0.63 mm. The proposed hybrid transducer and multimodal system open up a new way for designing multi-physical mechanism based NDEs.

Analysis of shear wave in a FGPE/FGPM structure with imperfect magneto-electro elastic bounding interface

An analytical approach has been taken into consideration to investigate shear wave propagation in a multiferroic composite FGPE/FGPM consisting of a functionally graded piezoelectric layer on a functionally graded piezomagnetic half-space. It is assumed that the interface in the composite is damaged mechanically, magnetically, or electrically. A well-known Wentzel–Kramers–BrillouinWKB asymptotic approach has been applied for the solution of the composite structure. Phase velocity has been calculated numerically for magneto-electrically open and short cases. Graphs have been plotted with respect to phase velocity and wavenumber for unraveling the effect of different parameters such as mechanical imperfection parameter, gradient parameters, and magneto-electro mechanical coupling parameters. These parametric studies yield mainly three conclusions: (a) The presence of mechanical imperfection parameter remarkably enhances the phase velocity, depending upon the values of wavenumber. (b) Phase velocity rises and falls for layer and half-space with the rising value of gradient parameters, while keeping the rest parametric values fixed, respectively. (c) The magnetomechanical coupling parameter increases the phase velocity for both magneto-electrically open and short cases, but the electromechanical coupling parameter decreases the phase velocity for both open and short cases. The present results have relevant applications in the non-destructive testing and evaluation of composite materials like FGPE/FGPM.

Quantitative evaluation of defects based on the characteristics of the induced eddy current field

A quantitative evaluation method for determining the shape, length and depth of surface defects is proposed for the purpose of non-destructive testing (NDT) and evaluation of metal materials. The COMSOL Multiphysics finite element software is used to calculate and analyse the eddy current magnetic field and the influence of the geometric parameters of defects on the spatial three-dimensional magnetic field distributions are studied. The results show that the shape of the surface defect can be judged from the measurement result of the x-Bx curve. The quantitative analysis of the crack length is realised according to the corresponding position of the peak (trough) of surface magnetic field Bz . The depth of the crack can be inversely calculated by the quantitative relationship between the trough depth of Bx (or the peak value of Bz) and the crack depth. Therefore, this method provides convenient and contactless detection technology in which the characteristic quantities corresponding to the defect parameters are independent from each other to improve the accuracy of defect evaluation.

Ultrasonic scattering in two-phase polycrystalline materials

Typically, many of the polycrystalline materials found in nature and those created using different manufacturing processes consist of multiple phases. Careful nondestructive characterization of these materials is of fundamental importance for quality assurance because microstructure is strongly correlated with mechanical performance. Ultrasonic scattering measurements have shown high sensitivity to material microstructure such that this approach is of interest for multi-phase materials. A fundamental understanding of scattering from idealized two-phase materials would provide essential information regarding the predictive nature of scattering measurements to quantify such microstructures. For this purpose, samples were created using spark plasma sintering (SPS) from mixtures with three different ratios (with respect to mass) of Cu and Fe powders. These elements do not alloy such that the resulting samples will not have any intermediate phases. Moreover, one pure Cu sample and one pure Fe sample were also sintered using SPS. The samples were imaged using electron backscatter diffraction (EBSD) to quantify the material organization. Ultrasonic backscatter and attenuation measurements were performed on the samples and the results were used for comparison with scattering models. Prospects for nondestructive evaluation of such materials are also discussed. [Work supported by Air Force Research Laboratory (AFRL) under prime contract FA8650-15-D-5231.]

Binarization Mechanism Evaluation for Water Ingress Detectability in Honeycomb Sandwich Structure Using Lock-In Thermography.

The growing use of composite honeycomb structures in several industries including aircraft has demonstrated the need to develop effective and efficient non-destructive evaluation methods. In recent years, active thermography has attracted great interest as a reliable technology for non-destructive testing and evaluation of composite materials due to its advantages of non-contact, non-destructive, full-area coverage, high speed, qualitative, and quantitative testing. However, non-uniform heating, low spatial resolution, and ambient environmental noise make the detection and characterization of defects challenging. Therefore, in this study, lock-in thermography (LIT) was used to detect water ingress into an aircraft composite honeycomb sandwich structure, and the phase signals were binarized through the Otsu algorithm. A square composite honeycomb with dimensions of 210 mm × 210 mm along with 16 different defective areas of various sizes in groups filled with water by 25%, 50%, 75%, and 100% of the cell volume was considered. The sample was excited at multiple modulation frequencies (i.e., 1 Hz to 0.01 Hz). The results were compared in terms of phase contrast and CNR according to the modulation frequency. In addition, the detectability was analyzed by comparing the number of pixels of water ingress in the binarized image and the theoretical calculation.

A Physics-Informed Neural Network for Quantifying the Microstructural Properties of Polycrystalline Nickel Using Ultrasound Data: A promising approach for solving inverse problems

We employ physics-informed neural networks (PINNs) to quantify the microstructure of a polycrystalline Nickel by computing the spatial variation of compliance coefficients (compressibility, stiffness and rigidity) of the material. The PINN is supervised with realistic ultrasonic surface acoustic wavefield data acquired at an ultrasonic frequency of 5 MHz for the polycrystalline material. The ultrasonic wavefield data is represented as a deformation on the top surface of the material with the deformation measured using the method of laser vibrometry. The ultrasonic data is further complemented with wavefield data generated using a finite element based solver. The neural network is physically-informed by the in-plane and out-of-plane elastic wave equations and its convergence is accelerated using adaptive activation functions. The overarching goal of this work is to infer the spatial variation of compliance coefficients of materials using PINNs, which for ultrasound involves the spatially varying speed of the elastic waves. More broadly, the resulting PINN based surrogate model shows a promising approach for solving ill-posed inverse problems, often encountered in the non-destructive evaluation of materials.