Ndt & E International最新文献

Cryo-ultrasonic testing utilizes polycrystalline ice coupling to enable the inspection of metallic components with complex shape. The relatively high velocity of compressional waves in ice (approximately 4000 m s⁻¹) and its ability to support the propagation of shear waves, significantly strengthen the ultrasonic transmission through curved interfaces over conventional water coupling. This paper explores the possibility of further enhancing the ultrasonic properties of ice by dispersing solid particles in water before it is frozen. Complex physicochemical phenomena occur when aqueous dispersions freeze which can lead to a solid material with microstructural characteristics that may be unfavorable to the propagation of ultrasonic waves. Here, these effects are controlled to produce a composite material consisting of alumina nanoparticles in an ice matrix. The composite exhibits compressional and shear wave velocities of approximately 4800 m s⁻¹ and 2700 m s⁻¹ , respectively. Importantly, the mass density of the material is more than twice as large as the density of water. Finally, it is shown that a phenomenon similar to a glass transition occurs during freezing which results in low ultrasonic attenuation when the temperature approaches – 100 °C.

This article presents a multi-modal hybrid-probe approach to nondestructive inspection of RCF cracks and damage in rails. A combination of electromagnetic (EM) and ultrasonic testing (UT) techniques are presented, which allows for complementary physics to be utilized to enhance detection and characterization of surface and sub-surface cracks in a non-contact manner at high speeds. A novel integrated design which combines the motion-induced eddy current (MIEC) effect and ultrasonic Rayleigh surface waves generated and detected using electromagnetic acoustic transducer (EMAT) is presented. The hybrid probe was tested at low speeds to demonstrate an increased damage localization capability. This was carried out using a data registration and fusion approach between the sensing modalities. Finally, the capability of MIEC effect at high-speeds is demonstrated. The results show that the hybrid probe has a high potential for in-motion, high-speed damage detection and characterization in the future.

In the laboratory, the density of pavement cores (cylindrical samples of hot mix asphalt (HMA) material taken from roads) is assessed using an electromagnetic (EM) bench consisting of two ultra-wideband (UWB) Vivaldi antennas and a vector network analyser (VNA). The main objective is to replace the nuclear gauge system currently used in the laboratory as the standard method for this purpose. Firstly, specific antipodal Vivaldi antennas have been adapted from the literature. Their dimensions are 7 × 7 cm with a bandwidth [1.5–15 GHz]. Secondly, a tomographic approach is compared with an analytical solution and a Finite-Difference Time Domain (FDTD) simulation, based on a time-domain estimation of the dielectric under test (DUT) with a single transmitter/receiver configuration. A laboratory validation is presented and the adapted antennas as well as the time domain approach show acceptable results for assessing the dielectric constant on known materials. Finally, to show that the proposed EM bench is a promising non-ionizing solution, the density or equivalent compactness of HMA cylindrical samples is estimated and compared with nuclear gauge results.

Multi-layer metal spherical shell structure is widely used as the core component of pressure-bearing equipment, deep-sea exploration equipment and other critical areas due to its plane stress uniformity and high specific strength. Its long-term service in complex and harsh environments will inevitably produce a variety of defects and damages, which will affect the safety of the equipment in service. Ultrasonic guided wave inspection is a potential non-destructive testing method, but the multilayer metal bonding structure between the metal and non-metal bonding layer impedance difference is large, resulting in defects located in the internal reflection signal is difficult to propagate to the outer layer with a sensor, the multilayer spherical shell structure itself leads to the complexity of the guided wave propagation characteristics, it is difficult to extract the individual modes of the time information for the defects of the detection and localization. Therefore, in this paper, we propose a probabilistic damage existence imaging method for spherical shell structures and combine it with the virtual time reversal technique to detect and localize the defects on the inner and outer surfaces of multilayered metallic spherical shell structures without benchmarks. The results show that the newly proposed method can realize the accurate localization imaging of internal/external defects of multilayer metal spherical shell structures.

Electrical resistance is closely related to the damage of ceramic matrix composites (CMC) such as matrix crack, crack opening distance (COD), and interphase retention rate, giving it the potential to become a new non-destructive testing (NDT) technique. An electro-mechanical experiment method was designed for the tensile test of ceramic matrix mini-composites (CMMC). An optical in-situ tensile test was performed to obtain the pattern of matrix crack propagation. The result confirms that matrix crack saturation may not occur before the material fractures. An electromechanical model considering the COD was established to identify the damage situations. A new method for preparing ceramic matrix micro-composites composed of a single fiber and a single-layer pyrolytic carbon (PyC) interphase was realized. The accurate in-situ resistivity of the PyC was measured based on the micro-composites.

The application of the UHF RFID technique in non-destructive testing (NDT) and structural health monitoring (SHM) has gained increasing attention due to its wireless, battery-less, and cost-effective attributes. It offers a promising approach for SHM and the Internet of Things (IoTs). This paper reports commercial off-the-shelf (COTS) flexible UHF RFID tag-based sensors for corrosion characterization on coated mild steel. Two types of COTS flexible UHF RFID tags with different bends are fabricated as sensors. The received signal strength indicator (RSSI) measurement is implemented to characterize the corrosion. Three parts (T-match area, dipole arms, and dipole loadings) of the two tags are tested for sensing purposes, and comparison and discussion of sensitivity, read range, and results are provided. This study successfully validates the feasibility of the proposed tag-bent method for corrosion characterization undercoating. It can be concluded that the dipole arm part of the applied COTS tags is the most sensitive area.

Switch rails are weak but essential components in a high-speed rail track system, which have an urgent non-destructive testing requirement due to aging and associated fatigue damage accumulation. They are settled under sophisticated operation environments, which causes them to have unpredictable damages, such as abrasion, exfoliation, and cracks. Our goal is to propose a reliable system to detect structural damages of switch rails. Using ultrasonic guided waves to examine the health status of switch rails makes it possible to continuously evaluate the health status of switch rails when they are in use. Conventional damage detection methods with ultrasonic guided waves such as baseline signal subtraction, independent component analysis-based methods cannot always make reliable detection results. These methods are either lack of powerful abilities to capture the characteristics of damaged signals or time-consuming to be operated in real damage detection tasks. In this paper, a convolutional neural network-based system is proposed to solve both of the above challenges simultaneously. The proposed model employs multiple convolutional layers to extract deep features of ultrasonic guided wave signals. These features are then fed into a classifier to predict whether they are damaged signals or not. To evaluate the proposed model performance, we collected ultrasonic guided wave signals from two different switch rails. The proposed model achieved more than 91% testing accuracy and outperformed other relevant methods. It also demonstrated the proposed model had strong generalization abilities to make it capable in practical switch rail structural damage detection tasks.

Electrical impedance tomography (EIT) is a method of spatially mapping the conductivity distribution of a domain and has been studied as a potential embedded sensing or nondestructive evaluation (NDE) tool. An often touted advantage of EIT is that it can be used in-situ; that is, because the method only requires the application of unobtrusive electrodes, it can conceivably be used while the component or structure is in operation. This material-as-the-sensor philosophy strongly aligns with key components of the NDE 4.0 vision such as the realization of intelligent cyber–physical systems (CPS) and digital twins. To date, however, the claim of in-situ sensing via EIT has not been significantly substantiated. This is problematic because operational loads induce strains that often change the conductivity of the material. Establishing that EIT can detect damage-induced conductivity changes through the presence of unrelated strain-induced conductivity changes is therefore important. To that end, we herein study the application of EIT for detecting indentation damage in a carbon fiber/epoxy composite as the composite is loaded in a four-point bend. It was found that the bending load changes the contact impedance of the electrodes, which resulted in poor EIT images when solving the EIT inverse problem with the ${\ell }_2$-norm on the error term. Using the ${\ell }_1$-norm on the error term, solved via the primal–dual interior point method (PDIPM), significantly improved image quality. Image quality was even further improved through the use of a mixed prior for regularization, and EIT images were compared to thermography with good agreement. These results show that EIT can indeed detect damage through the presence of an applied load, but care must be taken to account for factors such as outlier data arising from electrode degradation and changing contact impedance. Use of the ${\ell }_1$-norm on the error term is therefore highly recommended for in-situ imaging via EIT.

In the context of nondestructive testing and evaluation, dispersion entropy (DisE) stands out as a promising dynamic nonlinear health monitoring measure for rotating machineries. However, in high-noise scenarios, transient impulses linked to rotating machinery faults often get submerged under the noise component present in the collected vibration signal. As a result, DisE not only fails to detect the presence of a fault at the earliest stage of inception but also performs poorly in tracking the progression of the incepted fault. Aiming at overcoming the limitations of DisE in dynamic health monitoring of rotating machineries, in this paper, impulses corresponding to a fault is extracted by suppressing the unnecessary noise component by weighting the squared envelope of the collected vibration signal. Due to the application of weighted squared envelope in calculating the DisE, the proposed measure is termed as weighted squared envelope dispersion entropy (WSEDisE). Effectiveness of WSEDisE in dynamic health monitoring of rotating machineries is verified by two different experimental run to failure data collected from rolling element bearings and spur gears. Experimental results show that WSEDisE not only overcomes the weaknesses of original DisE but also demonstrates better performance than conventional entropy-based methods such as permutation entropy (PE) and advanced DisE based method namely multiscale DisE (MDisE).

The often-assumed measurement reciprocity between scanning laser detection and scanning laser excitation is disproved by a simple experiment. Nevertheless, a deeper study based on the reciprocity relation reveals correct reciprocal measurement set-ups for both the probe-excitation/laser-detection and the laser-excitation/probe-detection case. Similarly, the all-laser measurement, that is thermoelastic laser excitation with laser vibrometer detection, is not in general reciprocal with respect to the exchange of excitation and detection positions. Again, a substitute for the laser doppler vibrometer out-of-plane displacement measurement was found which ensures measurement reciprocity together with laser excitation. The apparent confusion in literature about strict validity/non-validity of measurement reciprocity is mitigated by classifying the measurement situations systematically.