Notch Defects Research Articles

A submillimeter notch visualization detection method based on local wavenumber imaging algorithm of broadband laser-generated surface-wave

Abstract Laser ultrasound is widely used in metal notch detection because of its non-contact, non-destructive and high accuracy, but there is still the problem of insufficient detection sensitivity. Therefore, this paper proposes a laser ultrasound-based broadband surface wave local wavenumber imaging algorithm to provide an effective method for the detection of surface notches by taking the aluminum alloy metal structure as the research object. Broadband surface waves on a metal plate are excited by a laser, and vibration information is obtained through vibrometer scanning with a Laser Doppler Vibrometer(LDV). It characterizes the surface notches in the wavenumber domain by filtering out the direct waves and retaining only the reflected surface waves of the new modes generated by the notches, successfully detecting and visually characterizing the tiny surface notches at the sub-millimeter level. The surface notch defect detection experiment was carried out using a laser ultrasound detection platform, and the surface notch with a width and depth of 0.1mm detection. The effectiveness of the method was verified by repeated experiments. The results of the study provide an effective surface notch detection method for metallic structures which has a broad application prospect.

Deficiency of DDX3X results in neurogenesis defects and abnormal behaviors via dysfunction of the Notch signaling

The molecular mechanisms underlying the neurodevelopmental disorders (NDDs) caused by DDX3X variants remain poorly understood. In this study, we validated that de novo DDX3X variants are enriched in female developmental delay (DD) patients and mainly affect the evolutionarily conserved amino acids based on a meta-analysis of 46,612 NDD trios. We generated a ddx3x deficient zebrafish allele, which exhibited reduced survival rate, DD, microcephaly, adaptation defects, anxiolytic behaviors, social interaction deficits, and impaired spatial recognitive memory. As revealed by single-nucleus RNA sequencing and biological validations, ddx3x deficiency leads to reduced neural stem cell pool, decreased total neuron number, and imbalanced differentiation of excitatory and inhibitory neurons, which are responsible for the behavioral defects. Indeed, the supplementation of L-glutamate or glutamate receptor agonist ly404039 could partly rescue the adaptation and social deficits. Mechanistically, we reveal that the ddx3x deficiency attenuates the stability of the crebbp mRNA, which in turn causes downregulation of Notch signaling and defects in neurogenesis. Our study sheds light on the molecular pathology underlying the abnormal neurodevelopment and behavior of NDD patients with DDX3X mutations, as well as providing potential therapeutic targets for the precision treatment.

Atomistic details of grain, crack, and notch effect on the mechanical behavior and fracture mechanisms of monolayer silicon carbide

Recently, sp2-hybridized single-layer SiC, analogous to graphene, has received much attention in nanoelectronics and nanoelectromechanical systems because of its remarkable thermal, electrical, and mechanical properties. However, the unique properties and related applications strongly depend on the growth of a single-crystal and large-area two-dimensional SiC. The majority of synthesized SiC monolayers exhibit a natural polycrystalline structure, comprising single-crystalline grains with diverse sizes and orientations. Moreover, the emergence of structural defects, including cracks and notches, poses challenges that are difficult to overcome during both the fabrication and subsequent processing stages. In this paper, we explore the atomistic details of grain, crack, and notch effect on the mechanical behaviors and fracture mechanisms of single-layer SiC using molecular dynamics simulations. Increasing grain size from 2 nm to 35 nm gradually increases the elastic modulus and fracture strength, which fits well with the inverse Pseudo Hall-Petch relationship. However, an anomalous trend of decreasing as well as increasing fracture strain is observed with the increasing grain size. For polycrystalline SiC with a 2 nm grain size, the elastic modulus and fracture strength are roughly 87% and 41% of those observed in single-crystalline SiC. Notably, when comparing the impact of rectangular crack and circular notch defects, the circular notch exhibited a more pronounced effect in diminishing mechanical behavior under both armchair and zigzag orientational loading. The circular notch produces considerable amorphization around the notch, but the rectangular crack does not show any significant dislocation or amorphization around the crack. The critical stress intensity factor, energy release rate, radial distribution function, and potential energy per atom are calculated to explain all the fracture properties. The effect of temperature and strain rate is also investigated for all the defect-induced samples. Overall, our results provide new insight and understanding of the mechanical behavior and fracture mechanisms of polycrystalline, crack- and notch-induced SiC, and set a standard for making and designing new nanodevices and nanostructures made of SiC.

Efficient second harmonic generation from nonlinear one-dimensional meta-grating metasurface under vertically incident pump laser excitation

The emergence of new materials will drive the development of a generation of devices. The purpose of this study is to realize the nonlinear optical frequency conversion in the novel material structure - metasurface structures. We study the second harmonic generation (SHG) from the all-dielectric resonant meta-grating metasurfaces with high quality (Q) factors. The quasi-bound states in the continuum (Q-BIC) modes can be easily induced using the linearly polarized plane wave with normal incidence. Two types of asymmetric one-dimensional meta-grating metasurfaces with square air notch defect and different widths based on AlGaAs are numerically investigated. When the symmetry of the AlGaAs meta-grating structures is broken, the BIC modes are transformed into the Q-BIC modes, which support strong local field confinement in the AlGaAs meta-grating array, thereby promoting the SHG conversion. When the pump laser intensity is about 5 MW/cm2, the two type structures provide the SHG conversion efficiencies about 0.059 and 0.166. The investigation results will promote the application of nonlinear metasurfaces in integrated nonlinear optical systems.

The genetic aspects of hidradenitis suppurativa

Genetic aspects have a substantial role in hidradenitis suppurativa (HS) pathogenesis. A positive family history of HS occurs in about one-third of HS cases and is significantly higher in patients with early onset of the disease. Recent twin studies have shown a high heritability in HS, fortifying the importance of genetic factors in disease pathogenesis. Based on existing knowledge on the genomics of HS, the disease can be categorized as familial HS, sporadic, syndromic HS, and “HS plus” associated with other syndromes. In familial HS, autosomal dominant transmission is proposed, and monogenic inheritance is rare. This monogenic trait is related to mutations of γ-secretase component genes and Notch signaling or defects in inflammasome function. With newly discovered gene mutations, such as those related to innate and adaptive immunity, skin microbiome, inflammasome, epidermal homeostasis, and keratinization pathway, we can define HS as a polygenic, multifactorial, autoinflammatory disease. To fully elucidate the genetic aspects of HS, we need extensive, long-term global collaborations.

Acoustic emission data classification of 18 percent Ni maraging steel 250 specimens during tensile deformation

ABSTRACT Acoustic emission (AE) evaluation is an important Nondestructive Testing technique. The technique is a whole field passive technique that detects defects that are growing during the application of force on the structure. At a certain threshold, AE starts emanating from the structure while the structure is stressed by tensile deformation. 18% Ni Maraging steel 250 grade material is widely used in the aerospace industry and exhibits fracture behaviour. In the current study, tensile specimens are used and acoustic emission (AE) parameters are recorded. Four types of specimens Type A, Type B, Type C and Type D specimens are designated as heat -affected zone, parent metal, defect-free weldment and weld with notch defect, respectively. These specimens are tensile deformed in order to obtain AE parameters at 60% of failure load (FL), 60–75% of FL, 75–90% of FL and 90% to FL. AE parameters – amplitude, ring down counts, duration, rise time, energy, RA value, DA value, hit rate, count rate and energy rate – are tabulated for various FLs. These parameters have vital importance in critical assessment of the structural integrity of 18% Ni Maraging steel 250 structures.

Characteristics and Applications of Current-Driven Magnetic Skyrmion Strings

We investigate the current-driven characteristics and applications of magnetic skyrmion strings by micromagnetic simulations. Under the spin-polarized driving current, the skyrmion string presents different moving trajectories in different layers due to the skyrmion Hall effect. Moreover, a series of skyrmion bobbers can be generated with a notch defect placed in the surface and the skyrmion bobbers will follow the skyrmion string. By varying the current density, the bobbers’ characteristics such as number and velocity can be manipulated, which inspires us to propose a skyrmion string-based diode. In addition, an AND logic gate and an OR logic gate in the identical scheme based on the skyrmion string are proposed. AND logic and OR logic behaviors can be realized by varying the driving current densities. Our findings will contribute to further research of magnetic skyrmion strings for data storage, processing, and energy-efficient computing.

Stress state at the root of variable-wall-thickness pipeline welded joint

In this study, root notch defects in the application of variable wall thickness designs of pipeline welded joints were analyzed. Considering variable-wall-thickness pipelines, various finite element models of butt-welded joints were established by changing the joint geometric parameters such as variable-wall-thickness ratio, butt misalignment, or variable wall thickness transition angle. This was followed by applying different internal working pressures of the pipeline to calculate the stress triaxiality and maximum principal stress near the root notch of the welded joints. The influence of the weld section shape and internal working pressure on the calculation results is summarized, and the corresponding fracture risk of the root notch is evaluated. Based on the aforementioned analysis, it was found that the root notch in the variable-wall-thickness joint reduced the safety of the welded joint. A greater irregularity of the joint geometric morphology results in a higher the stress triaxiality and maximum principal stress near the root notch, further severely increasing the brittle fracture risk of the joint.

Finite element analysis of fracture behavior in ceramics: Competition between artificial notch and internal defects under three-point bending

Evaluation of the nonlinear relationship between the surface defect size and fracture strength of ceramics is important for engineering applications. In this study, we aim to predict the apparent nonlinear relationship between the defect size and fracture strength of single-edge notched beams (SENBs) using the finite element method. Specifically, we applied the methodology for predicting fracture strength from microstructure distribution data (relative density, pore size, aspect ratio, and grain size) to a finite element analysis (FEA) model in which the shape and size of the initial defects are defined at notch locations. By reproducing the apparent nonlinearity caused by the competition between the surface and internal defects within the framework of linear elastic fracture mechanics, the effectiveness of the FEA methodology for the evaluation of strength scatter and allowable crack size in ceramics was demonstrated.

High incidence of cleft palate and vomer deformities in patients with Eustachian tube dysfunction

Although the cleft palate is regarded as a contraindication for Eustachian tube ballooning, the presence of submucosal cleft palate may be overlooked while diagnosing Eustachian tube dysfunction. Therefore, we aimed to determine the incidence of the presence of a hard palate bony notch and vomer defect, which indicate the presence of submucosal cleft palate in patients with Eustachian tube dysfunction. In the Eustachian tube dysfunction group (n = 28), 4 patients (14.3%) exhibited a hard palate bony notch and a concurrent vomer defect. Three of them exhibited the presence of occult submucosal cleft palate, which had not been diagnosed previously. None of the control group (n = 39) showed any of these findings. The hard palate length of patients in the Eustachian tube dysfunction group was significantly lesser than that of those in the control group (34.2 ± 5.6 mm vs. 37.2 ± 2.1 mm, P = 0.016). Patients with Eustachian tube dysfunction have a high incidence of submucosal cleft palate and its occult variant, which are challenging to diagnose without any preexisting suspicion. Clinicians should evaluate the hard palate and vomer to exclude the presence of occult submucosal cleft palate while diagnosing Eustachian tube dysfunction.

Phased array ultrasonic S-scan testing of near-detection-surface defects based on a background subtraction algorithm

In phased array ultrasonic sector scanning testing, echoes from defects near the detection surface are often overlapped with interface echoes and cannot be characterized. Based on linear acoustic theory, a mathematical model combining the background subtraction and the sum of squares differences algorithm is established to extract the characteristics of near-detection-surface defect echoes. The upper surface of the artificial notch defect is used as a near-detection-surface defect for detection. Specially, linear interpolation algorithm is used to suppress the effect of residual interface echo on the defect echo feature extraction and the effect of different interpolation factors is analyzed. The defect location and size were calculated based on the extracted defect characteristics. The simulation and experimental results indicate that the model can effectively extract the near-detection-surface defect echoes characteristics. Furthermore, when the interpolated signal reaches at least 500 MHz, residual interface echoes can be effectively suppressed. More importantly, according to the extracted defect echo characteristics, the localization and quantitative accuracies of near-surface defects can reach 0.2 mm and 0.3 mm, respectively. These findings provide an effective strategy for phased array ultrasonic sector scanning testing of near-detection-surface defects.

Image-Based Single-Molecule Analysis of Notch-Dependent Transcription in Its Natural Context.

Notch signaling is crucial to animal development and homeostasis. Notch triggers the transcription of its target genes, which produce diverse outcomes depending on context. The high resolution and spatially precise assessment of Notch-dependent transcription is essential for understanding how Notch operates normally in its native context in vivo and how Notch defects lead to pathogenesis. Here we present biological and computational methods to assess Notch-dependent transcriptional activation in stem cells within their niche, focusing on germline stem cells in the nematode Caenorhabditis elegans. Specifically, we describe visualization of single RNAs in fixed gonads using single-molecule RNA fluorescence in situ hybridization (smFISH), live imaging of transcriptional bursting in the intact organism using the MS2 system, and custom-made MATLAB codes, implementing new image processing algorithms to capture the spatiotemporal patterns of Notch-dependent transcriptional activation. These methods allow a powerful analysis of in vivo transcriptional activation and its dynamics in a whole tissue. Our methods can be adapted to essentially any tissue or cell type for any transcript.

Diffusive and Fluidlike Motion of Homochiral Domain Walls in Easy-Plane Magnetic Strips

Propagation of easy-plane magnetic precession can enable more efficient spin transport than conventional spin waves. Such easy-plane spin transport is typically understood in terms of a hydrodynamic model, partially analogous to superfluids. Here, using micromagnetic simulations, we examine easy-plane spin transport in magnetic strips as the motion of a train of domain walls rather than as a hydrodynamic flow. We observe that the motion transitions from diffusive to fluidlike as the density of domain walls is increased. This transition is most evident in notched nanostrips, where the domain walls are pinned by the notch defect in the diffusive regime but propagate essentially unimpeded in the fluidlike regime. Our findings suggest that spin transport via easy-plane precession, robust against defects, is achievable in strips based on realistic metallic ferromagnets and hence amenable to practical device applications.

Exploring high-frequency eddy-current testing for sub-aperture defect characterisation using parametric-manifold mapping

Accurate characterisation of small defects remains a challenge in non-destructive testing (NDT). In this paper, a principle-component parametric-manifold mapping approach is applied to single-frequency eddy-current defect characterisation problems for surface breaking defects in a planar half-space. A broad 1–8 MHz frequency-range FE-circuit model & calibration approach is developed & validated to simulate eddy-current scans of surface-breaking notch defects. This model is used to generate parametric defect databases for surface breaking defects in an aluminium planar half-space and defect characterisation of experimental measurements performed. Parametric-manifold mapping was conducted in N-dimensional principle component space, reducing the dimensionality of the characterisation problem. In a study characterising slot depth, the model & characterisation approach is shown to accurately invert the depth with comparable accuracy to an equivalent peak amplitude-phase inversion method. The approach is used to characterise the depth of a sloped slot demonstrating good accuracy up to ≈ 2.0 mm in depth over a broad range of frequencies, indicating applications in geometric feature inversion. Finally the technique is applied to finite rectangular notch defects of surface extents smaller than the diameter of the inspection coil (sub-aperture) over a range of sub-resonant frequencies. The results highlight the limitations in characterising these defects and indicate how the inherent modelling uncertainty around resonance can severely limit characterisation at these frequencies.

Semi-Precise Analytical Method for Investigating the Liftoff Variation on the Hall Sensor in Metal Defect Sensing.

Hall-effect sensors are used to detect metal surface defects both experimentally and numerically. The gap between the specimen and the sensor, called the liftoff, is assumed to remain constant, while a slight misplacement of a sample may lead to incorrect measurements by the Hall-effect sensor. This paper proposes a numerical simulation method to mitigate the liftoff issue. Owing to the complexity of conducting precise finite-element analysis, rather than obtaining the induced current in the Hall sensor, only the magnetic flux leakage is obtained. Thus, to achieve a better approximation, a numerical method capable of obtaining the induced current density in the circumferential direction in terms of the inspection direction is also proposed. Signals of the conventional and proposed approximate numerical methods affected by the sensor liftoff variation were obtained and compared. For small liftoffs, both conventional and proposed numerical methods could identify notch defects, while as the liftoff increased, no defect could be identified using the conventional numerical method. Furthermore, experiments were performed using a variety of liftoff configurations. Based on the results, considering the threshold of the conventional numerical method, defects were detected for greater liftoffs, but misdetection did not occur.

Scattering of Higher Order Mode Clusters (HOMC) from surface breaking notches in plates with application to higher temperature gradients

The potential of higher frequency ultrasonic guided wave mode cluster (HOMC) waves to be used for remote inspection of notch defects in plate-like structures is investigated, at room and elevated temperatures. Quantitative studies of HOMC interaction with notch defects ranging from 5% to 50% of plate thickness are performed using 2D finite element simulations, and are validated by controlled experiments performed, firstly at room temperature. Analysis using reciprocity-based relations is used to uncover for the first time, how the constituent modes of HOMC play a vital role in their scattering processes. Further experiments are used to show that the results are stable up to 300 ̊C, thereby demonstrating the feasibility of short range higher-resolution remote inspection of notch defects using non-dispersive higher frequency mode clusters in industrial conditions.

In situ study on the bending strain field of a Zr-based bulk metallic glass with notch

Full understanding of the ductility enhancement mechanism of bulk metallic glasses (BMGs) requires investigations of the strain field evolution under constrained load, which is still unclear in experiments to date. The present work in situ studied the strain field evolution of Zr50.7Cu28Ni9Al12.3 alloy with notch defects under three-point bending through the digital image correlation technique. It was revealed that the deformation was dominated by the normal strain along the specimen length direction and the shear strain which were highly localized into band-like pattern. The results experimentally prove the localized strain in shear bands. A linearly proportional relationship between the magnitude of strain maxima and notch diameter was unveiled as well, which gave rise to bending behaviors linearly dependent on notch size. Moreover, the strain evolution with testing time suggested that the deformation might be accomplished by a two-stage process which induced the multiple deformation regions on fracture surface. Our results provide experimental data and useful information about the bending deformation of BMGs, thus would shed more insights on developing theoretical model of BMGs mechanical behaviors.

A0 Mode Excitation and Defect Detection in Aluminum Beam Structure

As a method to realize the defect detection in beam structure, this paper constructs an EMAT-laser detection system to detect the notch defect in an aluminum beam. EMAT is designed as a transmitter to generate single Lamb wave mode. A high precision laser detector is used as a receiver to obtain the received signals. The defect is localized and quantified with the help of space-frequency-wavenumber analysis. The evaluated depth of the defect is 2.006 mm, while the actual size is 2 mm. It shows good agreement between the evaluated result and actual size, the error is only 0.3%. This method also can be used in the evaluation of defect in other materials.

Quantitative ultrasonic testing for near-surface defects of large ring forgings using feature extraction and GA-SVM

Water immersion ultrasonic testing technology is widely used in non-destructive testing of large ring forgings, but near-surface defects are difficult to identify in near-surface blind zone, because the defect echo always overlaps with interface echo. In this article, a method combining signal feature extraction with genetic algorithm optimization support vector machine (GA-SVM) was proposed to realize quantitatively testing of near-surface defects. Firstly, the near-surface artificial defects were machined on the test specimens from the large ring forgings, and a total of 160 signal samples were obtained by water immersion ultrasonic experiments. Then the time-domain features of ultrasonic signals were extracted, the spectrum features were obtained by fast Fourier transform. And the ultrasonic signals were processed by intrinsic time-scale decomposition, and the statistical features of the rotating components with different frequencies were extracted. Finally, three kinds of neural network classifiers were used to identify the size and depth of defects by the features database. The experimental results showed that the identification error of the GA-SVM classifier with the different number of sample databases was always minimal. The ultrasonic testing experiment of near-surface notch defects further verified the correctness and feasibility of the GA-SVM classifier.

Static notch sensitivity in orthotropic materials and composites

A theoretical study on defect and notch sensitivity in orthotropic materials is carried out, with the aim to make explicit the bridging between notch effect and defect sensitivity. Analogies and differences with the isotropic case are highlighted, and the relevant parameters necessary to quantify the transition from a fracture-mechanics-controlled to a notch-mechanics-controlled behaviour are discussed in details. The validity of the proposed approach is proven taking advantage of a bulk of experimental data taken from the literature and related to thermoplastic and thermosetting composite laminates with different stacking sequences and notch geometries.