Inspection Of Plates Research Articles

Defect identification based on wavelet decomposition for MFL non-destructive inspection of steel plates

The article considers an application of wavelet decomposition for defect identification based on the example of magnetic flux leakage (MFL) non-destructive testing (NDT). To solve this problem, a parallel signal decomposition is performed for several chosen types of mother wavelet. This article describes the criteria and algorithm for the choice of mother wavelet. A decision tree is used for defect classification. The algorithm presented has been tested both on imitations of defects and on an oil tank floor plate with natural defects.

Defect Detection and Identification of Point-Focusing Shear-Horizontal EMAT for Plate Inspection

As a kind of nondestructive testing (NDT) method, shear-horizontal (SH)-guided wave detection technology is widely used on an electromagnetic acoustic transducer (EMAT). Although ultrasonic-guided waves perform well in defect location, it is difficult to obtain detailed information about defects, and the low efficiency of EMAT energy conversion still reduces the EMAT’s performance. Therefore, in this work, the defect detection method of different shapes and sizes by point-focusing shear-horizontal (PFSH)-guided wave EMAT with the use of periodic permanent magnet (PPM) is investigated through simulation and experiment. For the purpose of defect classification and quantification, the extraction principles of defect features are obtained through simulation based on the circumferential scatter diagrams, and the neural network (NN) is used to process the features extracted from the experimental data. The results show that by extracting effective defect features from the scatter diagram, high-accuracy classification and high-precision quantification of defects under the influence of the focusing transducer can be achieved.

New Open Clusters Found by Manual Mining of Data Based in Gaia DR2

The physical nature of a series of 20 new open clusters is confirmed employing existing data on putative star members, mainly from second Gaia Data Release (DR2). The clusters were discovered as over-densities of stars by visual inspection of either photographic DSS plates or proper motion plots of random source fields. The reported objects are not present in the most comprehensive or recent catalogs of stellar clusters and associations. For all of them, clumps of co-moving stars are revealed in the proper motion space. The parallaxes of the clumped stars are compatible with the real existence of open clusters over narrow ranges of distances. Surface density calculations, free of most noise from non-member sources, allow in some cases differentiating a cluster core and an extended cluster corona. Color-magnitude diagrams generally show a definite main sequence that allows the confirmation of the physical existence of the clusters and some of their characteristics. Two of the new clusters seem to form a double system with a common origin. Several of the new clusters challenge the claim of near completeness of the known OC population in the distance range from 1.0 to 1.8 kpc of the Sun (Kharchenko et al. 2013).

Low frequency ultrasonic guided waves excitated by Galfenol Rod Ultrasonic Transducer in plate inspection

Lower frequency ultrasonic guided wave (20 kHz–200 kHz) has obvious advantages in large area plate monitoring. It enables longer propagation distances because of low attenuation and simple modes. The present study utilized a Galfenol Rod Ultrasonic Transducer (GRUT) excite low-frequency ultrasonic guided waves in plate inspection. It was verified by finite element simulation and experiment that GRUT can excite S0 mode Lamb wave, A0 mode Lamb wave and SH0 wave. A defects detection method based on A0 mode and S0 mode Lamb wave is proposed that “A0 mode Lamb wave is used for defect determination by its amplitude variation in time domain, and utilized S0 mode Lamb wave to locate the defect”. In this paper, utilize GRUT to detect a via hole with a radius of 2 cm, the experimental results show that the proposed method is convenient and fast with less signal processing, and the experimental error is 10.22 %.

Ultrasonic and thermographic studies for CFRP inspections with real and simulated defects

This paper deals with an overview of improved UT control procedures, related to defect investigation on advanced CFRP composite elements for aeronautical structures; the inspection procedures were evaluated with different frequency probes, employing direct contact, water stream and immersion methods. In this work, ultrasonic and thermographic controls of CFRP components are presented for detection of different types of defects (real and artificial) in order to evaluate sensitivity and detectability techniques. This work presents a preliminary ultrasonic study on CFRP components employing different probes and tools.For these aims, inspections of CFRP plates with artificial defects are optimized and compared to thermographic acquisitions with active pulsed technique, in order to calibrate Ultrasonic Technique tools and verify procedures for suitable results. In a second stage, improved ultrasonic scanning investigations are applied on real parts, containing real production defects in terms of small delamination and diffused porosity of T-shape stringer and resin/matrix excesses between layers, localized in the thin cap and web of structural civil aircraft stringers.

Guided ultrasonic wavefield cross-correlation with a curved array for high-resolution plate inspection

Abstract We present in this work an ultrasonic imaging technique based on wavefield cross-correlation that has potential for high-resolution inspecting of plates and plate-like structures. A curved transmit/receive array setup is used for acquiring wide-aperture waveform data beneficial for applying the presented imaging condition. An additional dispersion analysis using waveform data received by a linear array allows one to reveal the excited guided wave modes and possibly determine the shear wave velocity as an input parameter in the 3D wavefield simulation. Using synthetic but realistic data generated by realistic 3D simulations, we demonstrate the invariance of the time reversal process and the capability of the presented imaging approach for ultrasonic testing based on Lamb waves. In addition to the ability to localise and size multiple defects simultaneously, this imaging approach does not require baseline data and involves only minimal waveform data pre-processing.

Air coupled ultrasonic inspection with Lamb waves in plates showing mode conversion

In this paper we demonstrate a non-destructive, non-contact detection method for small defects in thin polymer plates using an air coupled ultrasonic (ACUS) setup. There exist many applications for such methods, e.g. quality control in the manufacturing process or failure prevention by periodical inspections during the lifetime of a product. We demonstrate a setup for the inspection of plates together with signal analysis algorithms to process the measured data, meeting the challenges to handle the dispersive signals and establishing a robust failure criterion.Pressure waves from the transmitter excite different modes of Lamb waves inside the plate. These Lamb waves propagate in the plate and reradiate pressure waves into the air that are then detected by the receiver. Lamb mode conversion is used for defect detection. A numerical model allows the visualization of the propagating waves in the air as well as the Lamb waves inside the plate.Four key parameters of the setup are identified, two angles and two distances. The transmitter and the receiver angles are used to select which Lamb mode (anti-symmetric A0 or symmetric S0) is mainly excited and detected, respectively. For the acquisition of the Lamb wave signal the distance from the transmitter to the receiver should be as large as possible but is limited by the attenuation of the signal. Measurements for different values of this distance are essential for signal analysis. The distance between transducer and plate surface should be as small as possible even if it may introduce secondary Lamb waves due to reflections of the pressure wave between transmitter and plate surface. Two algorithms, a model based one and a data driven one, are presented to separate Lamb modes that overlap in time. In these separated signals, the Lamb mode conversion from A0 to S0 is shown, allowing a localization of the defect.We conclude that defect detection and localization with Lamb mode conversion is possible with an air coupled ultrasonic setup. Multiple measurements along the propagation direction of the Lamb waves are necessary to allow a thorough signal analysis and visualize the mode conversion.

Unidirectional focusing of horizontally polarized shear elastic waves electromagnetic acoustic transducers for plate inspection

The ultrasonic guided wave testing method is very effective in monitoring the safety of complex structures. The fundamental shear horizontal (SH) wave mode has the advantage that the propagation velocity does not change with the frequency. However, accurately recognizing the ultrasonic signal is difficult due to the SH guided wave’s bidirectional propagation characteristics generated by the Lorentz force mechanism. Therefore, it is necessary to achieve unidirectional focusing of Lorentz force-generated SH guided waves. A newly designed SH guided wave electromagnetic acoustic transducer (EMAT) is proposed with an interlaced periodic permanent magnet (PPM) and AC coils of different phases. A 3D model based on the electromagnetic mode and the solid mechanics mode using COMSOL software is calculated and compared with the bidirectional focusing EMATs. The results show that there are many influencing factors in the structural design of the transducers, and the focal radius and the angle of the individual PPMs are discussed in this work. The results indicate that the new unidirectional EMAT shows superiority in many cases, and the decrease of the focal radius with a suitable aperture angle will increase the focusing intensity of the signal.

Signal Strength Enhancement of Magnetostrictive Patch Transducers for Guided Wave Inspection by Magnetic Circuit Optimization

Magnetostrictive patch transducers (MPT) with planar coils are ideal candidates for shear mode generation and detection in pipe and plate inspection with the advantages of flexibility, lightness and good directivity. However, the low energy conversion efficiency limits the application of the MPT in long distance inspection. In this article, a method for the enhancement of the MPT was proposed by dynamic magnetic field optimization using a soft magnetic patch (SMP). The SMP can reduce the magnetic resistance of the magnetic circuit, which increases the dynamic magnetic field intensity in the magnetostrictive patch during wave generation and restricts the induced dynamic magnetic field within the area around the coils for sensing during wave detection. Numerical simulations carried out at different frequencies verified the improvement of the dynamic magnetic fields by the SMP and influence of different affecting factors. The experimental validations of the signal enhancement in wave generation and detection were performed in an aluminum plate. The amplitude magnification could reach 12.7 dB when the MPTs were covered by the SMPs. Based on the numerical and experimental results, the SMP with a large relative permeability and thickness and close fitting between the SMP and coils were recommended when other application conditions were met.

QUANTIFYING PHOTOSTIMULABLE PHOSPHOR (PSP) PLATE ARTIFACTS TO STANDARDIZE RADIOLOGIC QUALITY ASSURANCE

Background With every use, photostimulable phosphor (PSP) plates accumulate physical artifacts (i.e., scratches, dents) that negatively affect image quality. Dental clinicians are responsible for monitoring these artifacts and discard plates they have deemed undiagnostic. Currently, at our institution, this is accomplished by direct visual inspection of plates for signs of wear. This arbitrary process has no objective validation leading to variability in radiologic image quality and may impair diagnostic value. Objective This study aimed to develop a metric to objectively quantify the severity of physical artifacts on PSP plates. This metric will be compared against the current standard of direct visual inspection to determine the validity of this approach for PSP quality assurance. Materials and Methods Sixty random PSP plates (CS 7600; Carestream Dental, Rochester, NY) were chosen for analysis: 36 were determined to be undiagnostic by using the current quality control standard, 20 were in active circulation, and 4 brand-new plates were used as controls. The selected plates were exposed to obtain the equivalent of a posterior bitewing image (Belmont PHOT-X II s Model 505 at 70 kV, 6 mA, 0.22 seconds), scanned, and raw DICOM images exported. A custom computer algorithm (MATLAB; Mathworks, Natick, MA) was developed to measure the inhomogeneity of the image to calculate the artifact metric. By using these, the selected plates were sorted and compared against the current quality assurance standard. Preliminary Results Preliminary results showed poor correlation between plates that were selected to be discarded by direct visual inspection and artifact metrics. Many plates that were chosen to be discarded with the current standard had a lower artifact metric compared with plates that were still in circulation. Future Directions Future studies aim to validate this metric by comparing the artifact score with qualitative grading of PSP plate artifacts and to determine a threshold for when radiologic diagnosis is impeded. With every use, photostimulable phosphor (PSP) plates accumulate physical artifacts (i.e., scratches, dents) that negatively affect image quality. Dental clinicians are responsible for monitoring these artifacts and discard plates they have deemed undiagnostic. Currently, at our institution, this is accomplished by direct visual inspection of plates for signs of wear. This arbitrary process has no objective validation leading to variability in radiologic image quality and may impair diagnostic value. This study aimed to develop a metric to objectively quantify the severity of physical artifacts on PSP plates. This metric will be compared against the current standard of direct visual inspection to determine the validity of this approach for PSP quality assurance. Sixty random PSP plates (CS 7600; Carestream Dental, Rochester, NY) were chosen for analysis: 36 were determined to be undiagnostic by using the current quality control standard, 20 were in active circulation, and 4 brand-new plates were used as controls. The selected plates were exposed to obtain the equivalent of a posterior bitewing image (Belmont PHOT-X II s Model 505 at 70 kV, 6 mA, 0.22 seconds), scanned, and raw DICOM images exported. A custom computer algorithm (MATLAB; Mathworks, Natick, MA) was developed to measure the inhomogeneity of the image to calculate the artifact metric. By using these, the selected plates were sorted and compared against the current quality assurance standard. Preliminary results showed poor correlation between plates that were selected to be discarded by direct visual inspection and artifact metrics. Many plates that were chosen to be discarded with the current standard had a lower artifact metric compared with plates that were still in circulation. Future studies aim to validate this metric by comparing the artifact score with qualitative grading of PSP plate artifacts and to determine a threshold for when radiologic diagnosis is impeded.

Technique for detecting flaws in metallic surfaces using an optical system with phase-type blazed gratings

ABSTRACTIn this paper, we evaluate a novel flaw-detection technique for metallic surfaces based on the use of phase-type blazed gratings. Transparent blazed gratings were prepared by the soft nanoimprint method involving the transfer of a template (a reflective grating structure used for spectroscopy) onto silicone rubber. The blazed gratings were then integrated into an imaging system to observe the reflective metal sample. Due to the low-pass-filtering properties of the gratings, the captured image was notably blurred. This characteristic aids in flaw detection on metallic surfaces because the captured image is adequate to distinguish flaws in the targeted area on the basis of the texture of the rough surface, including any other structures that were unintended. The use of double-sided gratings with crossing grating vectors was found to be efficient for homogenous low-pass filtering. Such flaw-detection techniques are expected to be useful for conducting quality inspections of rolled steel plates since the surface contains both a rough surface and undesirable flaws.

웨이블릿 합성 영상 및 엔트로피 기반 판별함수를 이용한 철강 후판 검사의 최적 조명메커니즘

웨이블릿 합성 영상 및 엔트로피 기반 판별함수를 이용한 철강 후판 검사의 최적 조명메커니즘

Signal noise based transfer function approach for reliability estimation of ultrasonic inspection

In recent years several methods for reducing the burden of experimentation for obtaining Probability of Detection (PoD) curves have been proposed, especially involving the use of numerical simulation. In particular, there is much interest in being able to estimate the PoD capabilities of a given NDE method, target embodiment and material, provided this is known for some canonical material for the same combination of method/embodiment. Ultrasonic experiments on materials with low signal to noise ratio (SNR) are often difficult and time consuming since the higher signal noise causes serious complications. Set in this context, this paper proposes an approach for transferring PoD curves among materials with different SNR values. The classical transfer function PoD approach is based on the hypothesis that the ratio of signals in related quadrants is equal, which requires large datasets for multiple quadrants. The approach proposed here directly deals with SNR instead of the ratio of signals, and thus requires only the experimental data of the parent application. The new approach is illustrated through example cases involving the prediction of PoD curves for ultrasonic inspection of an aluminium plate using the empirical PoD data for the same in austenitic stainless steel and mild steel. The approach is also demonstrated in each of the possible combinations among these three materials.

Ultrasonic Guided Wave-Based Circumferential Scanning of Plates Using a Synthetic Aperture Focusing Technique

Tanks are essential facilities for oil and chemical storage and transportation. As indispensable parts, the tank floors have stringent nondestructive testing requirements owing to their severe operating conditions. In this article, a synthetic aperture focusing technology method is proposed for the circumferential scanning of the tank floor from the edge outside the tank using ultrasonic guided waves. The zeroth shear horizontal (SH0) mode is selected as an ideal candidate for plate inspection, and the magnetostrictive sandwich transducer (MST) is designed and manufactured for the generation and receiving of the SH0 mode. Based on the exploding reflector model (ERM), the relationships between guided wave fields at different radii of polar coordinates are derived in the frequency domain. The defect spot is focused when the sound field is calculated at the radius of the defect. Numerical and experimental validations are performed for the defect inspection in an iron plate. The angular bandwidth of the defect spot is used as an index for the angular resolution. The results of the proposed method show significant improvement compared to those obtained by the B-scan method, and it is found to be superior to the conventional method—named delay and sum (DAS)—in both angular resolution and calculation efficiency.

The intravesical phallus in patients with cloacal exstrophy: An embryologic conundrum

Phalluses present inside the extrophied bladder of cloacal exstrophy (CE) newborns have been sporadically reported in the literature; this clinical entity has largely unknown origins and may represent an extremely rare anomaly of CE. Along with nearly doubling the number of reported intravesical phalluses in the literature, this study aims to outline the common anatomic features and discuss the implications for theories of CE embryogenesis. The authors retrospectively identified patients with CE and a potential intravesical phallus between 1997 and 2017at two high-volume centers. Information was obtained about karyotype, age at closure, neurologic and renal anomalies, diastasis, phallus anatomy, and phallus biopsy pathology. Six genotypic males met the inclusion criteria. Five of six had a diastasis greater than 6cm. Four of six had paired corporal bodies in the intravesical phallus, one had a single corporal body, and one had a corporal-like structure. Five of six patients had a phallus located midline in the caudal aspect of the bladder; one was located midline in the bladder dome. Phallic biopsies were obtained in three of six patients. Two showed glanular and corporal tissue while the other showed vascular proliferation morphologically similar to that of erectile tissue. Previous reports suggested that a superior vesicle fissure configuration, fusion of the corporal bodies, and fused bladder plates were common findings with an intravesical phallus. With the addition of new cases, the only consistent variable between patients is a phallus located anywhere along the bladder plate that can comprise a corporal-like structure, a single corporal body, or fused corporal bodies. These findings have implications for several embryologic theories. Although this is a retrospective review with a limited number of patients, the condition is exceedingly infrequent making it only observable retrospectively over decades at high volume centers. The study outlined common anatomic features of the intravesical phallus in cloacal exstrophy and discussed the subsequent embryologic implications. In cloacal exstrophy newborns with presumed aphallia, meticulous inspection of the bladder plate and biopsy of any potential phallic structures can prevent resection of phallic tissue.

Full non-contact laser-based Lamb waves phased array inspection of aluminum plate

Lamb waves defect detection technique is suitable to detect long-range defects and multi-defects in plates because of its attractive properties such as multi-modes, low attenuation, and multi-defect sensitivity. As the laser beams have the tiny size and noncontact property, in this paper a full non-contact laser-based Lamb waves phased array inspection technique was proposed for defect detection in an aluminum plate. A Q-switched Nd: YAG pulse laser generating Lamb waves and a continuous laser inspection system was used to inspect the out-of-plane displacements. The laser-generated Lamb waves have the broadband property and low temporal resolution that are not suitable for defects detection directly. So the continuous wavelet transform was used to extract narrowband signals from laser-generated Lamb wave and a linear mapping algorithm was adopted to compensate for the dispersion of the extracted narrowband signals. Two experiments were carried out to verify the applicability and effectiveness of the developed full non-contact laser-based Lamb waves phased array inspection technique. Two compact phased array imaging algorithms, the total focusing method and the sign coherence factor algorithm, were adopted to image the defects with processed signals. The experimental results accurately located the positions of the defects.

철강후판 검사를 위한 웨이블릿 기반 판별함수 모델링 및 최적 조명계 선정

철강후판 검사를 위한 웨이블릿 기반 판별함수 모델링 및 최적 조명계 선정

Development of omnidirectional A0 mode EMAT employing a concentric permanent magnet pairs with opposite polarity for plate inspection

This work presents an omnidirectional electromagnetic acoustic transducer (EMAT) for generating and receiving A0 mode of Lamb waves in plate structures. The proposed EMAT is composed of a spiral meander coil (SMC) and a new concentric permanent magnet pairs with opposite polarity (CPMP-OP) for enhancing the generation and detection of A0 mode. A finite element model was established to simulate the directions of the static magnetic field produced by the permanent magnets and the incentive process of guided waves. To verify the performance of the EMAT, several experiments were performed. Firstly, we experimentally verified that the developed EMAT could generate and receive a pure single A0 mode omnidirectionally. Then, the relationship between the frequency response characteristic of the developed EMAT and the interval l (the distance between the two adjacent annular wires of the SMC) were explored. Furthermore, the circumferential consistency of the transducer was well demonstrated. Finally, the sensing performance of the developed omnidirectional A0 mode EMAT employing a CPMP-OP was compared with that of EMAT with different structures of coils and permanent magnets. The experimental results indicated that the developed omnidirectional A0 mode EMAT employing a CPMP-OP could enhance the signals of the A0 mode.

Integrated optical Mach-Zehnder interferometer-based defect detection using a laser-generated ultrasonic guided wave.

The laser-based transmitter used in this Letter is composed of an integrated optical Mach-Zehnder interferometer, which was first used in fault diagnosis. With the help of the effective signal processing method and laser-based integrated optical Mach-Zehnder (IOMZ) system, the location of the defect in an aluminum plate can be successfully determined. Moreover, a comparison study is conducted to investigate the effectiveness of both the conventional laser spot source and the IOMZ interferometer-based laser source. The results indicate that the IOMZ interferometer-based method can be very useful to the nondestructive testing research field. The potential for industrial applications is also significant, especially for the health monitoring and integrity inspection of metal plates.

Optimized inspection design for the thermographic characterization of sub-pixel sized through cracks

Non-destructive evaluation of structural components is critical for reducing costs from unnecessary replacements and maintenance. We study the utility of a non-contact modality for the inspection of thin metal plates for the presence of through cracks. Sensitivity to early stages of deterioration allows for simpler and less expensive repair than if a flaw propagates and becomes more damaging. Hence, we focus on the characterization of very small cracks with a thermal imaging technique. Through cracks interact with the flow of heat within a component, so that the characterization of cracks from a thermal image amounts to solving an inverse problem to discover unknown parameters that describe the crack.We consider cracks with length of less than a millimeter, falling under the pixel resolution of the recording thermal camera. Although these flaws are not directly visible from imaging data, the well-understood theory of heat conduction can be used in inference of crack properties. Herein we present a method to design an inspection modality that yields optimal data for such inference. Numerical experiments are performed to compare our optimized inspection setup to previous thermographic inspection scenarios found in the literature. Our design is found to produce the same quality of inference as these previous experiments which require much more expensive equipment (e.g. more powerful lasers and more sensitive IR cameras).