Nondestructive Testing And Evaluation Research Articles

Study of Rayleigh waves interaction with a spherical ball in contact with a plane surface for the development of new NDT method for ball bearings

The monitoring of the integrity of the spherical balls inside a ball bearing can be challenging, as it needs to be disassembled in order to access every element of the structure. In this paper, an ultrasonic method is used to directly interrogate the spherical solids. The interaction wave-solid lets us extract material related information. The complex geometry of the ball bearing is simplified to a repetitive assembly of an elementary unit of a solid sphere setting on a plane surface. Understanding of the interaction between the ultrasonic wave and this elementary block is the key to a more general comprehension of the interaction with the complete ball bearing. To achieve this, the interaction between a Rayleigh Surface Acoustic Waves (SAWs) propagating on a plane and a spherical solid ball setting on that plane is studied, numerically and experimentally.In the experimental configuration, a steel ball is fixed to an aluminum block. Shear wave contact transducers are used to generate SAWs, while a laser vibrometer is employed to precisely measure the ensuing displacements. Subsequently, the collected time series data is carefully visualized and analyzed to discern distinct waves, such as the Rayleigh wave on the block, SAW on the sphere, and the waves generated by the sphere. To complement these experimental findings, a numerical model is created using finite element analysis, faithfully reproducing the experimental conditions. This approach facilitates a comprehensive examination of the displacement field, both on the surface of the sphere and the aluminum block.The extraction of the material related information of the spherical ball is based on the estimation of the resonance frequency of each vibrational mode of the solid sphere. Furthermore, 3D Gabor and dispersion curves from the spatio-temporal signals are used to estimate and analyze these frequencies and to compare the different waves involved in the interaction: the direct Rayleigh waves, the back-generated waves and the waves propagating on the surface of the sphere. The findings demonstrate that the transmitted waves toward the block (back-generated wave) preserve the waveform of the SAW propagating on the sphere, enabling the deduction of the dispersive behavior and extraction of material properties, such as the Rayleigh wave group velocity.The implications of this study are particularly relevant for non-destructive testing and evaluation (NDTE) of ball bearings, as the research provides insights into characterizing their integrity without disassembling them. The ability to extract material information from signals measured at the outer ring of ball bearings holds promise for practical applications in assessing their condition.

A Hybrid Approach of Data-driven and Physics-based Methods for Estimation and Prediction of Fatigue Crack Growth

Lamb-wave-based nondestructive testing and evaluation (NDT/E) methods have drawn much attention due to their potential to inspect plate-like structures in a variety of industrial applications. To estimate and/or predict fatigue crack growth, many research efforts have been made to develop data-driven or physics-based methods. Data-driven methods show high predictive capability without the need for physical domain knowledge; however, fewer data can lead to overfitting in the results. On the other hand, physics-based methods can provide reliable results without the need for measured data; however, small amounts of physical information can worsen their predictive capability. In real applications, both the measurable data and the physical information of systems may be considerably limited; it is thus challenging to estimate and/or predict the crack length using either the data-driven or physics-based method alone. To make use of the advantages and minimize the disadvantages of each method, the work outlined in this paper aims to develop a hybrid approach that combines the data-driven and the physics-based methods for estimation and prediction of fatigue crack growth with and without Lamb wave signals. First, with Lamb wave signals, a data-driven method based on signal processing and the random forest model can be used estimate crack lengths. Second, in the absence of Lamb wave signals, a physics-based method based on an ensemble prognostics approach and Walker’s equation can be used to predict crack lengths with the help of the previously estimated crack lengths. To demonstrate the validity of the proposed approach, a case study is presented using datasets provided in the 2019 PHM Conference Data Challenge by the PHM Society. The case study confirms that the proposed method shows high accuracy; the RMSEs for specimens T7 and T8 are calculated as 0.2021 and 0.551, respectively. A penalty score is calculated as 7.63, this result led to a 2nd place finish in the Data Challenge. To the best of the authors’ knowledge, this is the first attempt to propose a hybrid approach for estimation and prediction of fatigue crack growth.

Parameter measurement of cable lead sealing using an eddy current system

Lead sealing is one of the key accessories for high-voltage cables and its quality directly affects the security and stability of such cables. In order to reduce the accident rate in power processing caused by lead sealing issues, it is necessary to carry out non-destructive testing and evaluation. Due to the bending surface of lead sealings, it is difficult to detect their conductivity and thickness accurately using existing eddy current (EC) testing methods. In this paper, measurements of conductivity and thickness for curved specimens are analysed and an accurate method is subsequently proposed. Firstly, the measurement methods of conductivity and thickness are established based on the transformer model. It is found that the conductivity and thickness can be detected using phase signature at high and low frequencies, respectively. Secondly, the influence of curvature on the phase signature is analysed and the conductivity and thickness measurements of lead sealing are corrected using curvature correction coefficients. Finally, an EC system is built and experiments are carried out to evaluate the novel methods. The results show that the methods achieve a good level of accuracy in detecting the conductivity and thickness of curved lead sealings.

Field Inspection of High-Density Polyethylene (HDPE) Storage Tanks Using Infrared Thermography and Ultrasonic Methods

High-density polyethylene (HDPE) is widely used for above-ground storage tanks (ASTs). However, there are currently no guidelines for the non-destructive testing (NDT) and evaluation (NDE) of HDPE ASTs. Moreover, the feasibility, limitations, and challenges of using NDT techniques for the field inspection of HDPE ASTs have not been well established. This study used both infrared thermography (IRT) and ultrasonic testing (UT) for the field inspection of HDPE ASTs. Highlighting the implementation challenges in the field, this study determined that: (1) ambient environmental parameters can affect IRT accuracy; (2) there is an ideal time during the day to perform IRT; (3) the heating source and infrared camera orientation can affect IRT accuracy; and (4) with proper measures taken, IRT is a promising method for flaw detection in HDPE ASTs. Additionally, UT can be used following IRT for detailed investigation to quantify the size and depth of defects. The manuscript concludes with a discussion of the limitations and best practices for the implementing of IRT and UT for HDPE AST inspections in the field.

Heat‐sealing integrity assessment through nondestructive evaluation techniques

Sealing is a critical step in different packaging industries. In heat sealing as one of the major types of sealing processes, two layers of materials (typically thermoplastics) are joined together through the application of heat and pressure load for a certain sealing time. Due to the capabilities of the heat‐sealing process to seal different kinds and sizes of packages, it has a wide range of applications in many different industries such as the packaging of food and medical products. The quality and integrity of sealings produced by these techniques are crucial for the quality and safety of the contained materials. In this paper, different types and processes of sealing are discussed. Due to the variations in shape, size, and complexity of the sealing region, quality testing and inspection of these products is a challenging task. Nondestructive testing and evaluation (NDTE) techniques can be promising tools to overcome these challenges. Furthermore, a detailed study of various types of potential defects and their generation mechanism in heat sealing is presented. Then, various types of NDTE techniques that can be potentially used for the inspection of heat‐sealing regions and their working principles, as well as their strength and weakness in sealing inspection, are debated. Finally, several cases of sealing inspection and relevant NDTE techniques that are developed as standard procedures are presented. The discussions in this study provide useful information for the selection and implementation of appropriate quality inspection and inline quality monitoring of sealing parts and processes.

Review of Shearography for Dual-Directional Measurement

Shearography is a coherent optical technique that allows the identification of the first derivative of deformation in the shearing direction. Due to direct measuring strain information, shearography is suited for non-destructive testing and evaluation (NDT/NDE). However, if there is a small defect parallel to the shearing direction, the first derivative of deformation in the direction has no noticeable change, and the defect is not visible. Therefore, the development of a shearography system with dual-directional simultaneous measurement of the first derivatives of deformation both in x- and y-directions is highly demanded in the field of NDT/NDE. It is suited to inspect complicated defects, such as long and narrow slots, microcracks, etc. This paper presents a review of shearography for different dual-directional systems developed in the last two decades. After a brief overview of shearography, the paper will display two dual-directional shearographic techniques—temporal phase-shift (TPS) and spatial phase-shift (SPS) methods. TPS dual-shearing systems are suited for static measurements, while the SPS dual-shearing systems are useful for dynamic measurements. The basic theories, optical layouts, and comparisons are presented. The advantages and disadvantages of practical applications are discussed.

NDE Outlook: Informatization of NDT and NDE

Informatization is defined as the process by which information technologies, such as the World Wide Web and other communication technologies, have transformed economic and social relations to such an extent that cultural and economic barriers are minimized. What does this mean for nondestructive testing and evaluation (NDT/E)? In short: informatization in NDT and NDE has happened and will continue to happen, independent of whether individuals or companies like it or not. However, we can shape it—together.

Subsurface damage detection and structural health monitoring using digital image correlation and topology optimization

Detecting subsurface defects in structural members is a challenging yet important part of condition assessment of structures. Existing methods in this regard are either based on nondestructive evaluation and testing (NDE/T), or structural health monitoring (SHM) concepts. NDE/T methods require expensive equipment usually based on wave propagation or radiation imaging. Damage detection based on SHM usually relies on global vibration response which has proven successful in informing the existence and sometimes coarse-grained location information about damage, but is fairly limited in reconstructing the 3D shape of internal damage. This paper proposes to leverage full-field response data obtained by digital image correlation (DIC) in a topology optimization framework to reconstruct the internal damage in members. In other words, this paper shows how perturbations in observable full-field surface measurements can be used as a proxy to detect unobservable internal abnormalities.An initial finite element model of the structure is first created to discretize the member into elements whose constitutive properties are treated as unknowns in the optimization problem. The goal of the optimization is to minimize the discrepancies between the observed full-field response measured experimentally using DIC, and that computed numerically using the model. To that end, an objective function is first computed as the sum of residuals by mapping both responses onto a common grid, which is then pushed to a minimum via the method of moving asymptotes (MMA) as the optimization algorithm.The framework was evaluated on a series of simulated and real-world experiments using steel coupon specimens with artificially manufactured defects. Results show that the proposed method is capable of detecting and reconstructing the location, extent, and shape of the damage with average F1-scores of 82.8% and 69.6% on simulated and real experiments, respectively. Furthermore, a detailed sensitivity analysis demonstrated the effect of various factors on the performance of the proposed approach, including different optimization starting points, defect severity, sensing density, and discretization density. Results from this study have demonstrated that the proposed method is able to successfully extract detailed internal damage information that is otherwise expensive and difficult to achieve with state-of-the-art methods and can therefore be used as a promising subsurface damage detection method.

Nondestructive Evaluation 4.0: Ultrasonic Intelligent Nondestructive Testing and Evaluation for Composites

ABSTRACT With the continuous promotion of Industry 4.0, the mass production of composites will be entering Industry 4.0 in the near future. With respect to quality control, nondestructive testing and evaluation (NDT&E) will become nondestructive testing and evaluation (NDE) 4.0 to seamlessly connect with Industry 4.0. Therefore, it is essential to develop innovative NDT&E methods and techniques for NDE 4.0. Although there are many facets of NDE 4.0, intelligent nondestructive testing and evaluation (iNDT&E) can be considered as a technical core of NDE 4.0. Therefore, we propose the development of iNDT&E techniques for composites. In this study, the development processes for NDE 1.0–4.0 are analyzed. The basic connotations of iNDT&E are discussed, and the basic framework and technical elements of iNDT&E are examined. As combined with ultrasonic iNDT&E for composites, the basic progress in iNDT&E techniques is reviewed from the perspectives of ultrasonic equipment, technology and methods, processes, and result evaluations and standards. Future development directions are presented for the iNDT&E techniques in NDE 4.0 for composites.

NDT/NDE by means of a probabilistic differential compressive sensing method

A novel microwave imaging (MI) method is proposed to deal with the nondestructive testing and evaluation (NDT/NDE) of dielectric structures. The proposed technique exploits a probabilistic differential contrast source inversion (D-CSI) formulation of the inverse scattering (IS) problem, which is then effectively solved by means of a customized multi-task Bayesian compressive sensing (MT-BCS) solver. Numerical results are shown to assess the effectiveness and robustness of the proposed NDT/NDE method, as well as to compare it. with a single-task (ST-BCS) implementation within the same framework.

Automated Defect Detection and Characterization on Pulse Thermography Images Using Computer Vision Techniques

Defect detection and characterization plays a vital role in predicting the life span of materials. Defect detection using appropriate inspection technologies at various phases has gained huge importance in metal production lines. It can be accomplished through wise application of non-destructive testing and evaluation (NDE). It is important to characterize defects at an early stage in order to be able to overcome them or take corrective measures. Pulse thermography is a modern NDE method that can be used for defect detection in metal objects. Only a limited amount of work has been done on automated detection and characterization of defects due to thermal diffusion. This paper proposes a system for automatic defect detection and characterization in metal objects using pulse thermography images as well as various image processing algorithms and mathematical tools. An experiment was carried out using a sequence of 250 pulse thermography images of an AISI 316 L stainless steel sheet with synthetic defects. The proposed system was able to detect and characterize defects sized 10 mm, 8 mm, 6 mm, 4 mm and 2 mm with an average accuracy of 96%, 95%, 84%, 77%, 54% respectively. The proposed technique helps in the effective and efficient characterization of defects in metal objects.

A nonlinear Kernel-based adaptive learning-by-examples method for robust NDT/NDE of conductive tubes

ABSTRACTIn this work, the real-time non-destructive testing and evaluation (NDT/NDE) of faulty conductive tubes from eddy current (EC) measurements is addressed and solved in a computationally efficient way by means of an innovative learning-by-examples (LBE) methodology. More specifically, the estimation of the descriptors of a defect embedded within the cylindrical structure under test (SUT) is yielded by combining a non-linear feature extraction technique with an adaptive sampling strategy able to uniformly explore the arising feature space. Predictions are then performed during the on-line testing phase by means of a support vector regression (SVR). Representative results from a numerical/experimental validation are reported to assess the effectiveness of the proposed approach also in comparison with competitive state-of-the-art approaches.

A blind test of nondestructive underground void detection by ground penetrating radar (GPR)

Blind test/experiment is widely adopted in various scientific disciplines like medicine drug testing/clinical trials/psychology, but not popular in nondestructive testing and evaluation (NDTE) nor near-surface geophysics (NSG). This paper introduces a blind test of nondestructive underground void detection in highway/pavement using ground penetrating radar (GPR). Purpose of which is to help the Highways Department (HyD) of the Hong Kong Government to evaluate the feasibility of large-scale and nationwide application, and examine the ability of appropriate service providers to carry out such works. In the past failure case of such NDTE/NSG based on lowest bid price, it is not easy to know which part(s) in SWIMS (S – service provider, i.e. people; W – work procedure; I – instrumentation; M – materials in the complex underground; S – specifications by client) fails, and how it/they fail(s). This work attempts to carry out the blind test by burying fit balls (as voids) under a site with reinforced concrete road and paving block by PolyU team A. The blind test about the void centroid, spread and cover depth was then carried out by PolyU team B without prior information given. Then with this baseline, a marking scheme, acceptance criteria and passing mark were set to test six local commercial service providers, determine their scores and evaluate the performance. A pass is a prerequisite of the award of a service contract of similar nature. In this first attempt of the blind test, results were not satisfactory and it is concluded that ‘S–service provider’ and ‘W–work procedure’ amongst SWIMS contributed to most part of the unsatisfactory performance.+

Guided Wave Propagation and Damage Detection in Composite Pipes Using Piezoelectric Sensors

Composite materials have many attractive properties, e.g. light-weight combined with high mechanical strength, and are recognized as an enabling technology for deep-water high pressure high temperature (HPHT) and corrosive environment applications. However, composite still has a barrier to entry in relation to steel due to limited field experience and lack of systematic failure prediction and assurance of in-service performance. Advances in such areas would enable the use of composites in a wider range of applications. Evaluation of in-service prototypes offers a partial solution but is costly. Thus a method that allows constant health monitoring of the composite in real-time and in-situ would be extremely useful. Ultrasonic guided wave-based structural health monitoring (SHM) technology is one of the most prominent options in non-destructive evaluation and testing (NDE/NDT) techniques. To investigate the feasibility of guided wave-based SHM for composite pipes, propagation characteristics of guided waves in an epoxy hybrid carbon/glass fibres pipe are systematically studied using finite element (FE) simulation and experiments. Both axisymmetric modes of propagation, the longitudinal L(0,n) and torsional T(0,n) modes are considered in the simulation process, however only the longitudinal modes can be captured by the piezoelectric sensors. Additionally, the tuning curves experimentally plotted are used to obtain the frequency with the maximum amplitude of each guided mode. Finally, guided waves in the composite pipe are tested with artificial defects (gel coupled coins) to understand the behaviour of guided waves after interaction with the defects. The different condition of artificial defects, e.g., the defect size and defect location are studied to find out the proper condition and limitation of using guided waves to monitor and inspect composite pipes.

Propagation of guided waves in pressure vessel

Pressure vessels usually operate under extremes of high/low temperatures and high pressures. Defect, such as crack and corrosion, can result in leakage or rupture failures, even catastrophic incidents. Guided wave-based structural health monitoring (SHM) technology is one of the most prominent options in non-destructive evaluation and testing (NDE/NDT) techniques. Propagation of guided waves in a typical pressure vessel is systematically investigated in this study for the application of guided wave-based SHM. Shape of the pressure vessel is a cylinder with two end caps. Because of geometric similarity, theory of guided wave propagation in the cylinderical structure is analyzed to study dispersive features of guided waves in the pressure vessel. Dispersion curves of three different types of guided wave modes, viz. the longitudinal, torsional and flexural modes, are calculated using theoretical method. Based on the analyses and experimental wave signals, central frequency and wave parameters of incident wave are optimized. Effect of contained liquid on propagation of guided waves, especially the L(0, 2) mode, in the pressure vessel is further investigated to minimize energy leakage of the wave to the contained liquid. The analytical method, finite element analysis (FEA) and experiments are applied to study propagation characteristics of guided waves in the pressure vessel, so as to demonstrate the feasibility of guided wave-based non-destructive evaluation and testing (NDE/NDT) for such kind of complex structures.

Use of Direct Active Thermal Imaging Technique for Sub Surface Delamination Detection in Aviation Composites

Various non-destructive testing and evaluation (NDTE) techniques are in use by the aviation industry. Thermal imaging as an NDTE tool for composite material is becoming an effective methodology. In this research, a direct energy method approach to active thermal imaging is applied with test specimen placed between the heating source and the camera to take only one diagnostics snap per unit area of region of interest (ROI). Purpose of this study is to assess the utility of direct method as a reliable NDTE technique during aerospace inspections as a quick ‘Go / No Go’ tool for the detection of sub-surface delamination in multilayered composite sheets. The research presents a quantitative comparison of temperature profiles as well as qualitative analysis of 2D active infrared thermo graphic testing of glass fiber epoxy to detect sub-surface delamination. The experimental results are in close agreement with the actual locations of delamination in test samples. The technique may serve as a reliable tool to quickly categorize the component under inspection. However, the size of delamination could not be ascertained with acceptable accuracy in this study, possibly due to the spread of epoxy to the delaminated regions during preparation of defective samples.

European Wood NDT & NDE Research and Practical Applications

The pioneering studies on non-destructive testing (NDT) and evaluation (NDE) of wood have been introduced in early 20 th century in Europe as it is in North America. Several improvements were recorded since then in NDT&NDE technologies with parallel to the development in wood industry. A wide range of NDT technologies are currently being used successfully for evaluating wood and wood based materials in many areas from the inspection of artifacts to on-line production control in plants all over the world. Today, research and technology transfer efforts are underway throughout the world to further the development and use of nondestructive methods to address the many challenges that arise with using forest resources. This study aims to review the NDT/NDE research efforts and their practical applications being conducted in Europe that is significant contributors to the international research and development activities.

Fuzzy similarity measures for detection and classification of defects in CFRP

The systematic use of nondestructive testing assumes a remarkable importance where on-line manufacturing quality control is associated with the maintenance of complex equipment. For this reason, nondestructive testing and evaluation (NDT/NDE), together with accuracy and precision of measurements of the specimen, results as a strategic activity in many fields of industrial and civil interest. It is well known that nondestructive research methodologies are able to provide information on the state of a manufacturing process without compromising its integrity and functionality. Moreover, exploitation of algorithms with a low computational complexity for detecting the integrity of a specimen plays a crucial role in real-time work. In such a context, the production of carbon fiber resin epoxy (CFRP) is a complex process that is not free from defects and faults that could compromise the integrity of the manufactured specimen. Ultrasonic tests provide an effective contribution in identifying the presence of a defect. In this work, a fuzzy similarity approach is proposed with the goal of localizing and classifying defects in CFRP in terms of a sort of distance among signals (measure of ultrasonic echoes). A field-programmable gate array (FPGA)-based board will be also presented which implements the described algorithms on a hardware device. The good performance of the detection and classification achieved assures the comparability of the results with the results obtained using heuristic techniques with a higher computational load.

Special Issue on Nondestructive Evaluation and Testing for Bridge Inspection and Evaluation

Special Issue on Nondestructive Evaluation and Testing for Bridge Inspection and Evaluation

A GMR–ECT based embedded solution for applications on PCB inspections

Abstract Real-time non-destructive testing and evaluation (NDT/E) of conducting materials using eddy current techniques (ECTs) has gained significance in the last few years. This paper proposes a real-time application of ECT–NDT system exploiting giant magneto-resistive (GMR) sensors for inspection of printed circuit boards (PCBs). Probe design aims to crack inspection over flat surface, especially suitable for micro-defect detection on high density bare PCB. We propose a system based on a GMR sensor able to detect the magnetic field resulting from the interaction between a planar coil exciter and PCBs. The EC signals, detected by the GMR sensor, have been acquired by a high speed analog-to-digital (A/D) converter, for a subsequent application of signal processing based on digital techniques. The achieved results have highlighted the efficient design of the system. The advantages of the proposed models and some possible improvements of the system are also discussed.