Nondestructive Testing Applications Research Articles

The improved scintillation performances and X-ray imaging of Lu2O3:Pr3+ nanoparticles induced by Sm3+ doping

Lu2(1-x)Pr2xO3 nanoscintillators (x = 0.0005, 0.001, 0.0015, 0.003, 0.005) with excellent red emission and a response time of 185.7 μs were synthesized by a coprecipitation method. It is found that both photoluminescence and radioluminescence intensities show an initial rising and then decreasing trend with increasing Pr3+ concentration and the strongest intensity can be obtained at x = 0.001. By determining the average distance between Pr and O, the radiative transition processes from 3P0 and 1D2 to 3H4 and nonradiative transition process from 3P0 to 1D2 can be confirmed. Meanwhile, the afterglow level of Lu2O3:Pr3+ nanoscintillators with an average size of 112.3 nm was found to be 2190 ppm. Based on the spectral data and density functional theory calculations, the afterglow can be related to PrLu· traps due to the presence of Pr4+ in Lu2O3:Pr. When Sm3+ ions were doped into Lu2O3:Pr3+, it is found that it leads to the decreased creation of Pr4+, the reduced afterglow level and the improved radioluminescence. By means of Lu2O3:Pr3+, Sm3+ nanoparticles being dispersed into polymethyl methacrylate (PMMA) polymer, PMMA-Lu2O3:Pr3+, Sm3+ composite films with fast response time and radiation resistance were prepared by a rotating coating method. The static X-ray imaging with a spatial resolution of 5.5 lp/mm using the composite film as an imaging screen was realized at extremely low safe dose of 4.6 μGy. Meanwhile, for the broken electric wire used as an object, the clear X-ray image can be observed. Our results suggest that Lu2O3:Pr3+, Sm3+ nanoscintillators have potential applications in medical imaging and nondestructive testing.

Nanoscale surface profile measurement using state space approach in digital holographic microscopy

Surface profile measurement at the nanoscale level has important applications in non-destructive testing and evaluation. The paper proposes a robust method for surface profilometry using digital holographic microscopy setup. The proposed method relies on extracting the phase map encoded in the hologram signal, which directly corresponds to the surface profile, using state space approach. The main advantage of the proposed method is high robustness against noise, which is demonstrated using numerical simulations. For designing the experimental system, a combination of Raspberry-Pi computer and camera module is used for hologram acquisition and processing, which is a step towards low cost imaging. For surface profile measurement, the experimental system has both temporal and spatial sensitivity parameters within 5 nanometers, which indicates robust design. In addition, experimental results show that the proposed method shows superior performance compared to the existing methods for measuring 100 nanometers surface profile features corresponding to different micro-structure regions of a standard calibration test target. Overall, the proposed method allows for single shot, non-contact and full-field measurement of nanoscale surface profile with additional benefits of noise robustness and low cost imaging design.

Application of Non-Destructive Testing Technology in Quality Testing and Control of Water Conservancy Projects

In view of social development, the demand for water conservancy engineering applications continues to increase. The number and scale of water conservancy projects in China have been in a state of continuous expansion in recent years. As a result, how to achieve efficient testing and effective control of the quality of water conservancy projects has always been a topic of discussion in the field of water conservancy engineering in our country. This paper summarizes the application of non-destructive testing technology in the quality testing and control of water conservancy projects. On the basis of explaining the connotation and application advantages of non-destructive testing technology, the non-destructive testing application strategies for concrete strength, steel corrosion and shallow cracks in water conservancy projects were studied.

Chromium doped broad-band near-infrared emission Mg4Ta2O9: Cr3+ phosphor excited by blue light for NIR-LEDs

Near-infrared light has a wide range of applications in imaging, non-destructive testing, and anti-counterfeiting. Fluorescence conversion method is one of the important methods for making near-infrared (NIR) LED light sources. In this work, we synthesized a novel Cr3+-doped Mg4Ta2O9 system, which can emit NIR light with a peak around 850 nm under the excitation of blue light at 460 nm. It has a broad emission spectrum with full width at half maximum (FWHM) of 178 nm, covering the first NIR region and extending to the second NIR region. The structure, luminescence properties, and applications of this NIR luminescent material have been studied in detail. Cr3+ occupies two six-coordinated Mg2+ sites in this system. The emission spectrum shows an anomalous phenomenon of red-shift with the increase of doping concentration, which is the result of the competition between the crystal field strength and the Jahn-Teller effect. The luminescent material can still maintain 82% of the luminous intensity at 150 °C. By combining with blue InGaN chips, NIR light-emitting optical devices were fabricated, and their potential applications in biological tissue penetration and non-destructive testing were demonstrated.

A novel wave tomography method for defect reconstruction with various arrays

In order to reconstruct the possible defects on the plate surface with arrays, a new wave tomography method based on the method of moments is established in this paper. According to the relationship between the probe number and grid amount, two algorithms, that is, the neural network and principal component analysis (PCA), are proposed and used to solve the ill-conditioned inversion equations. The neural network makes imaging feasible even if input data are not enough, and the PCA can greatly improve the computational efficiency via reducing the matrix dimension. Both numerical simulations and experimental measurements are conducted with the algorithm’s correctness and high precision validated. After investigating the influence of probe number on imaging quality, it is demonstrated that the algorithm can exactly predict the defect location when the input scattering data is not enough or fewer probes are arranged. More probes are needed for reconstructing the specific shape and thickness, especially when multiple defects are included. The qualitative results and quantitative data are conducive to providing some reference for engineering applications in nondestructive testing and structural health monitoring.

Development of Digital Shearography for Dual Sensitivity Simultaneous Measurement Using Carrier Frequency Spatial Phase Shift Technology

<div class="section abstract"><div class="htmlview paragraph">Digital shearography has many advantages, such as full-field, non-contact, high sensitivity, and good robustness. It was widely used to measure the deformation and strain of materials, also to the application of nondestructive testing (NDT). However, most digital sherography applications can only work in one field of view per measurement, and some small defects may not be detected as a result. Multiple measurements of different fields of view are needed to solve this issue, which will increase the measurement time and cost. The difficulty in performing multiple measurements may also increase for cases where the loading is not repeatable. Therefore, a system capable of measuring dual fields of view at the same time is necessary. The carrier frequency spatial phase shift method may be a good candidate to reach this goal because it can simultaneously record phase information of multiple images, e.g. two speckle interferograms with different fields of view. It then obtains the phase information of each interferogram by separating them from the spectrum using the Fourier Transform (FT) method. The challenge of using this method is that the phase information can partially overlap on the spectrogram, resulting in a bad phase map. This paper presents a new idea for separating the phase information on the spectrogram. The new idea adjusts the shearing directions, leading to complete separation of the spectrums of the two images, e.g. one in the horizontal direction and the other in the vertical direction. The phase information of each interferogram can then be excavated by windowing the corresponding spectrum and taking the inverse Fourier Transform. In digital shearography, the phase information is directly related to gradient of surface deformation; thus, gradient of surface deformation with different fields of view, also called dual sensitivity, can be obtained. The principle of this method will be described and demonstrated by experiment results.</div></div>

Printable Perovskite Diodes for Broad-Spectrum Multienergy X-Ray Detection.

Multienergy X-ray detection is critical to effectively differentiate materials in a variety of diagnostic radiology and nondestructive testing applications. Silicon and selenium X-ray detectors are the most common for multienergy detection; however, these present poor energy discrimination across the broad X-ray spectrum and exhibit limited spatial resolution due to the high thicknesses required for radiation attenuation. Here, an X-ray detector based on solution-processed thin-film metal halide perovskite that overcomes these challenges is introduced. By harnessing an optimized n-i-p diode configuration, operation is achieved across a broad range of soft and hard X-ray energies stemming from 0.1 to 10's of keV. Through detailed experimental and simulation work, it is shown that optimized Cs0.1 FA0.9 PbI3 perovskites effectively attenuate soft and hard X-rays, while also possessing excellent electrical properties to result in X-ray detectors with high sensitivity factors that exceed 5 × 103 and 6 × 104 µC Gy-1 cm-2 within soft and hard X-ray regimes, respectively. Harnessing the solution-processable nature of the perovskites, roll-to-roll printable X-ray detectors on flexible substrates are also demonstrated.

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

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.

Near-Field Imaging of Dielectric Components Using an Array of Microwave Sensors

Microwave imaging is a high-resolution, noninvasive, and noncontact method for detecting hidden defects, cracks, and objects with applications for testing nonmetallic components such as printed circuit boards, biomedical diagnosis, aerospace components inspection, etc. In this paper, an array of microwave sensors designed based on complementary split ring resonators (CSRR) are used to evaluate the hidden features in dielectric media with applications in nondestructive testing and biomedical diagnosis. In this array, each element resonates at a different frequency in the range of 1 GHz to 10 GHz. Even though the operating frequencies are not that high, the acquisition of evanescent waves in extreme proximity to the imaged object and processing them using near-field holographic imaging allows for obtaining high-resolution images. The performance of the proposed method is demonstrated through simulation and experimental results.

Massive Ultrasonic Data Compression Using Wavelet Packet Transformation Optimized by Convolutional Autoencoders.

Ultrasonic signal acquisition platforms generate considerable amounts of data to be stored and processed, especially when multichannel scanning or beamforming is employed. Reducing the mass storage and allowing high-speed data transmissions necessitate the compression of ultrasonic data into a representation with fewer bits. High compression accuracy is crucial in many applications, such as ultrasonic medical imaging and nondestructive testing (NDT). In this study, we present learning models for massive ultrasonic data compression on the order of megabytes. A common and highly efficient compression method for ultrasonic data is signal decomposition and subband elimination using wavelet packet transformation (WPT). We designed an algorithm for finding the wavelet kernel that provides maximum energy compaction and the optimal subband decomposition tree structure for a given ultrasonic signal. Furthermore, the WPT convolutional autoencoder (WPTCAE) compression algorithm is proposed based on the WPT compression tree structure and the use of machine learning for estimating the optimal kernel. To further improve the compression accuracy, an autoencoder (AE) is incorporated into the WPTCAE model to build a hybrid model. The performance of the WPTCAE compression model is examined and benchmarked against other compression algorithms using ultrasonic radio frequency (RF) datasets acquired in NDT and medical imaging applications. The experimental results clearly show that the WPTCAE compression model provides improved compression ratios while maintaining high signal fidelity. The proposed learning models can achieve a compression accuracy of 98% by using only 6% of the original data.

Correlation between compressive strength of concrete and ultrasonic pulse velocity: A case of study and a new correlation method

Concrete strength assessment is an important topic in evaluating existing structures. Formerly, only destructive tests were employed, limiting the number of tests due to their complexity and cost. Nowadays, the application of non-destructive tests has been booming to determine material strength, offering a more accessible and cheaper strategy than its counterpart. Non-destructive strategies are based on two steps: (1) the identification of the correlation between the concrete strength and another parameter that is easy to measure in situ, and (2) the use of this easy-to-measure parameter to infer the concrete strength in any desired element of the structure. The most common parameter adopted for this purpose is the Ultrasonic Pulse Velocity (UPV). However, the correlation between concrete strength and UPV must be determined via destructive experiments. From the research perspective, attention has focused on determining the correlation coefficient and the range of credibility for estimating the inferred concrete strength. Despite it, this strategy has remained elusive in the fundamental understanding and accounting of the joint dispersion of the concrete strength and the UPV. The present work addresses this knowledge gap by proposing a new correlation method based on probability interpretations to infer the compressive concrete strength from in-situ UPV measurements and including the dispersion evidenced in UPV measurements in both steps mentioned. The results demonstrated that it is possible to determine the confidence interval for the concrete compressive strength given a certain percentile of the UPV measured in situ. Finally, the application of the proposed method is illustrated through a case study, which is representative of different building pathologies. This novel proposal is a foundation to deal with the uncertainties involved in non-destructive tests, inspiring future advances in this field.

Time-of-Flight measurement on a rail by laser-ultrasound

Stress states of thermal origin on the Continuously Welded Rail (CWR) are a source of possible inconvenience due to winter breakage or dangerous summer buckling. To date, alongside procedures based on the measurement of rail displacements or rail cutting, several methods for measuring the stress state in the rail have been proposed, based on X-ray diffraction, Barkhausen noise, and the acoustoelastic effect; all these approaches have some critical issues for extensive use in the field. The acoustoelastic method is based on the dependence of the ultrasonic wave speed on the stress state of the material and involves the measurement of the Time of Flight (ToF). Because of the modest acoustoelastic effect, the speed variations caused by the stress states are very limited, which is reflected in the need for ToF measurements with an accuracy of the order of a few nanoseconds.In the past, the research group successfully used the acoustoelastic method to monitor a 3 km portion of a rail between Florence and Pontassieve, with fixed measurement stations, where the ultrasonic probes were permanently positioned on the neutral axis of the rail. Today, the need is to have a mobile measuring system, which can measure in several points or even continuously as the system moves along the rail. This appears to be possible through the use of, for example, non-contact systems such as those based on laser and air-coupled probes or lasers alone. In the first case, however, the acoustic wave partly propagates in the air before reaching the piezoelectric probe, and this path is subjected to variations in temperature and thus ToF. In the second case, the ultrasonic waves are generated and detected by optical methods with lasers. For the generation of acoustic waves, the use of pulsed lasers has become a widespread, reliable practice, which allows researchers to obtain signals of high amplitude and wide bandwidth. For the reception of the acoustic signal, the precision required in the measurement involves careful analysis and experimentation to identify the most appropriate laser technique, depending on the quality of the surface on which the measurement is performed, the sensitivity of the method, and the possibility of taking measurements while moving.In the present work, a technique for laser detection of ultrasonic waves, Optical Beam Deflection (OBD), is analysed. The technique is based on the deflection of an optical beam: the beam irradiates the surface of the rail and is reflected at angles that depend on the orientation of the surface at the point of measurement, which is perturbed by the passage of the acoustic wave. The technique, developed in the 1990s, has limited applications in non-destructive testing, where interferometer-based techniques are more widespread; still, they require more sophisticated and expensive equipment. Different experimental arrangements and initial experimental results are analysed and presented, to optimise their sensitivity and verify their suitability for the purpose.

Prospects on ultrasound measurement techniques with optical fibers

Ultrasound sensors have been widely used in medical imaging, as well as structural health monitoring (SHM) and non-destructive testing (NDT) in civil and mechanical structures. Covering entire structures and imaging large areas requires multiplexing of many ultrasound sensors with single readout instrument, which can be difficult for traditional piezoelectric transducers. Optical fiber-based sensors offer numerous advantages such as being lightweight, small, the ability to be embedded, immunity to electro-magnetic interference, and the ability to be multiplexed and distributed ultrasound sensors. Fiber ultrasound sensors are regarded as an ideal sensing solution for SHM and NDT, and even most recently for medical imaging due to its broadband ultrasound response and distributed capability. Micro and nanofibers are made smaller than telecom fibers using a wider selection of sensing materials with higher bending capability, which makes them ideal for high frequency (hundreds of MHz) ultrasound detection of micrometer cracks and imaging biological tissues. New optical materials and fabrication techniques are shaping the future with exceptionally small ultrasound sensors and actuators, extending the range of applications in SHM, NDT and medical imaging with higher accuracy and better precision over larger areas.

Research on the Development and Application of Acoustic Testing Technology

Taking the commonly used acoustic detection technology as the research object, the working principle of different types of acoustic detection technology and the application of adverse geological forecasting and nondestructive testing in the geotechnical field are described, and the advantages and disadvantages of different types of acoustic detection technology are pointed out through the discussion of the development of acoustic detection technology.

Design and Development of a High-Sensitivity, Portable, and Low-Cost Fluxgate Magnetometer

Fluxgate magnetometers are widely used, as they exhibit high sensitivity, while operating at room temperature. However, their cost, as well as the need for additional external units (e.g., power supply, data acquisition units, and so on), may act as negative factors. In this article, a new fluxgate magnetometer is presented based on a pulsed excitation signal, offering low power consumption and high sensitivity, while being low-cost and small. It can operate in open-loop or closed-loop mode, depending on the application and the strength of the externally imposed magnetic fields. The sensor’s racetrack topology, consisting of two excitation coils and one sensing coil, eliminates the effect of the sensor’s excitation field, in order to detect only the externally imposed magnetic field. Moreover, an additional coil is used to compensate the external magnetic field during the closed-loop operating mode. The device is completed with the required electronics and a microcontroller to generate the sensor’s excitation signal, receive its output, and compensate the magnetic background through proportional–integral–derivative (PID) control. Measurements can be transmitted in a wired or wireless manner to the desired device (e.g., personal computer, smartphone, and so on). The printed circuit board (PCB) of the sensor was designed and manufactured, including the electronics, as well as a rechargeable lithium battery to demonstrate the portability of the sensor. The final device was mounted in a 3-D printed enclosure, enabling its use under a variety of conditions. Initial measurements show that the sensor can act as a magnetic anomaly detector, exhibiting high sensitivity. As a result, it can be used for geomagnetic, biomedical, non-destructive testing, and other applications.

Application of Non-destructive Testing (NDT) Techniques on Reinforced Concrete Structure: A Review

Abstract: To properly maintain our public infrastructure, engineers and designers must learn different methods of inspection. An exhaustive review has been carried out for different aspects of non- destructive testing (NDT) adopted for RCC structures. NDT evaluates the remaining operation life of different components of structure. It provides an accurate diagnosis which allows prediction of extended life operation beyond the designed life. Different aspects are considered which includes condition assessment, durability, corrosion, condition ranking and service life of structures. In this review, several non-destructive inspection methods are evaluated, with the aim of identifying those, which are practical for detecting defects at early in the production sequence as possible. The methods used for carrying out non destructive analysis used by different investigators are also discussed. Merits and demerits of each method are also stated. RCC structures considered are reinforced buildings, bridges, ESRs, recently developed NDT techniques which are useful for prediction of performance of structure are also included.

Multi-Layer Material Characterization at Ka-Band Using Bayesian Inversion Method

This paper presents the implementation of the Bayesian inversion method for the characterization and estimation of different dielectric material properties. The scattering parameters of single and multi-layer materials are measured using a free-space experimental setup using a standard gain horn antenna and a Vector Network Analyzer (VNA) at Ka-band (26–40 GHz). The relative permittivity, material thickness, and material positioning error are defined as model parameters and estimated using the observed (measured) data. The FR4 Epoxy, Rogers RT/Duriod 5880, and Rogers AD600 with different relative permittivities and thicknesses are used in the measurement setup. The results displayed good agreement between model parameters and estimated properties of the presented materials, while the corresponding eigenvectors provided a level of confidence in model parameter values. The results were compared with different reported techniques to showcase the possible use of the presented method in microwave imaging, non-destructive testing, and similar applications.

A Simultaneous Pipe-Attribute and PIG-Pose Estimation (SPPE) Using 3-D Point Cloud in Compressible Gas Pipelines.

An accurate estimation of pipe attributes, pose of pipeline inspection gauge (PIG), and downstream pipeline topology is essential for successful in-line inspection (ILI) of underground compressible gas pipelines. Taking a 3D point cloud of light detection and ranging (LiDAR) or time-of-flight (ToF) camera as the input, in this paper, we present the simultaneous pipe-attribute and PIG-pose estimation (SPPE) approach that estimates the optimal pipe-attribute and PIG-pose parameters to transform a 3D point cloud onto the inner pipe wall surface: major- and minor-axis lengths, roll, pitch, and yaw angles, and 2D deviation from the center of the pipe. Since the 3D point cloud has all spatial information of the inner pipe wall measurements, this estimation problem can be modeled by an optimal transformation matrix estimation problem from a PIG sensor frame to the global pipe frame. The basic idea of our SPPE approach is to decompose this transformation into two sub-transformations: The first transformation is formulated as a non-linear optimization problem whose solution is iteratively updated by the Levenberg-Marquardt algorithm (LMA). The second transformation utilizes the gravity vector to calculate the ovality angle between the geometric and navigation pipe frames. The extensive simulation results from our PIG simulator based on the robot operating system (ROS) platform demonstrate that the proposed SPPE can estimate the pipe attributes and PIG pose with excellent accuracy and is also applicable to real-time and post-processing non-destructive testing (NDT) applications thanks to its high computational efficiency.

A High‐Q Terahertz Metamaterials Absorber for Refractive Index Sensing

Herein, a high‐Q terahertz metamaterials perfect absorber is proposed. The absorption, physical mechanism, and refractive index sensing are investigated by using the finite element method. The results indicate that for B‐mode and D‐mode, the Q values are as high as 1160.41 and 1276.31, which are at least one order of magnitude higher than previously reported. The sensitivity S and the figure of merit (FOM) are 1078.00 GHz RIU−1, 170.03 and 518.00 GHz RIU−1, 75.29, respectively. It can be seen that the B‐mode is more suitable for sensing application than the D‐mode. The effective sensitivity Seff is presented to characterize the effect of the analyte thickness h on the sensing sensitivity. The study finds that the Seff of the B‐mode is greater than one when h is in the range of 9–10 μm, namely, the sensor has the highest sensitivity. In view of the aforementioned advantages, the proposed sensor has potential applications in nondestructive testing and biosensors.

Design and analysis of a hybrid magnetic shielding system: application for the magnetic non-destructive testing of circuits

A magnetic shielding system combining three-axis active magnetic shielding and a high-Tc superconducting ring (TASR) was developed. The active shield mainly responds to DC field while the ring operates for shielding AC fields below 1 kHz. In this study, the system’s shielding effects were evaluated experimentally, and the results suggest that this system can effectively shield the interference of static and low-frequency magnetic fields to ensure the operation of high-precision magnetic sensors. The shielding factor reached 99.9% for geomagnetic field (DC, 38 500 nT), which exceeded 98% for about 10 000 nT AC magnetic field at 30–1000 Hz. Then, magnetic non-destructive testing of the circuit was performed in this TASR shielding system. The images clearly showed the magnetic field distribution in different kinds of circuits that could be inverted to current density information, indicating that the shielding system can detect circuit defects and has great application potential in integrated circuit diagnosis.