Rectangular Defects Research Articles

MOEMS-based accelerometer sensor using photonic crystal for vibration monitoring in an automotive system

Diagnosing the vibration in automobiles is a priority since it provides comfort to the passenger inside vehicle. This paper presents MOEMS accelerometer sensor by using photonic crystal. A spring mass system with photonic crystal technology is visualised and scrutinised. An optical sensing system with photonic crystal technology was studied and simulated with rods in air and holes in slab configuration. The applied force deflection of rectangular defect slab for vertical and horizontal movement is verified. Gaussian pulse propagated through the defect region in a photonic crystal slab resulted in wavelength shift for each defection of slab. Transmission spectrum was obtained for each deflection direction of slab and configurations. Q factor analysed for each displacement of slab found to be 3,210 for HIS vertical movement. It is found that distinct change in wavelength obtained for holes in slab configuration during vertical and horizontal movement of a slab compared to the results of rods in air configuration. High quality factor and sensitivity improvement obtained in this work showed feasibility of future fabrication for HIS and RIA configuration-based MOEMS sensor for vibration monitoring system.

Assessment of corroded API 5L X52 pipe elbow using a modified failure assessment diagram

Pipe elbows (bends) are considered critical pressurized components in the piping systems and pipelines due to their stress intensification and the effect of bend curvature. They are prone and hence more exposed to different corrosion failure modes than straight pipes. Late detection of such elbow damages can lead to different dangerous and emergency situations which cause environmental disasters, pollution, substantial consumer losses and a serious threat to human life. A comprehensive safety and reliability assessment of pipe elbows, including usage of prediction models, can provide significant increases in the service life of pipelines. It is well known that the limit pressure is an important parameter to assess the piping integrity. In this paper, the integrity assessment of damaged pipeline elbows made of API 5L X52 steel was done within the framework of numerical modeling using the finite element method (FEM) and finite element analysis (FEA). The evaluation of numerically FEM modeled limit pressure in the corroded elbow containing a rectangular parallelepiped-shaped corrosion defect with rounded corners at the intrados section was done and compared to different codes for calculating limit pressure. Moreover, the area with the corrosion defects with different relative defect depth to wall thickness ratios was FEM modeled at the intrados section of the pipe elbow where the highest hoop stress exists. The results showed that the codes for straight pipes could not be applied for the pipe elbows due to the significantly higher error in the obtained limit pressure value compared with numerically FEM obtained results. However, the results for modified codes, adapted for the pipe elbow case using the Goodall formula for calculation of the hoop stress in pipe elbows with defects are pretty consistent with the numerical FEA results. The notch failure assessment diagram (NFAD) was also used for the straight pipe and pipe bends with different corrosion defect depth ratios, while the obtained critical defect depth ratios further highlighted the criticality of pipe elbows as an essential pipeline component.

Theoretical studies of dual optical and acoustic unidirectional filtering based on two-dimensional phoxonic crystals with rectangle defects

ABSTRACT Dual optical and acoustic unidirectional transmission in two-dimensional phoxonic crystal rectangular defect connected by two mutually perpendicular waveguides is theoretically achieved. The unidirectional filtering for both optical and acoustic waves is designed by altering the phoxonic crystal waveguides and cavity to obtain the modes’ match and mismatch via the finite element method. This kind of devices has the abilities of mode convertor, wavelength filtering and unidirectional propagation for both the optical and acoustic wave, and maybe potentially applied in simultaneously manipulating light and sound.

Shape Effect of Surface Defects on Nanohardness by Quasicontinuum Method.

Nanoindentation on a platinum thin film with surface defects in a rectangular shape and triangular shape was simulated using the quasicontinuum method to study the shape effect of surface defects on nanohardness. The results show that the nanohardness of thin film with triangular defects is basically larger than those with rectangular defects, which is closely related to the height of the surface defects at the boundary near to the indenter. Moreover, the triangular defect might have an enhancement effect on nanohardness by a certain size of the defects and the boundary orientation of the defect, where such an enhancement effect increases as the defect grows. Furthermore, the nanohardness decreases when the defect is folded from wide to narrow in the same atom cavity, and particularly expresses a more obvious drop when the height of the defects increases. In addition, larger sizes of the rectangular defect induce more reduction in nanohardness, while the nanohardness of the triangular surface defect is sensitive to the periodic arrangement of atoms changed by the boundary orientation of the defect, which is well explained and demonstrated by the calculation formula theory of necessary load for dislocation emission.

Defect size estimation in rolling element bearings with angled leading and trailing edges

Rolling element bearings eventually become worn and develop surface defects, such as spalls, dents, and pits. Previous researchers have used bearings with defects that have sharp rectangular edges to develop methods for the estimation of the size of a defect. However, these idealized rectangular defects do not occur in the real world, they are in fact sloped. Tests on bearings with sloped edges on the entry and exit of the defect exhibited similar vibration characteristics as bearing with sharp 90° edges. A new defect size estimation method was developed to improve the accuracy in estimating the size of a defect that has sloping leading and trailing edges. A large dataset was obtained and has been made publicly available.

Non-destructive characterisation and evaluation of manufacturing defects in SiCf/SiC composites using the relative energy attenuation behaviour of X-rays

Silicon carbide fibre/silicon carbide (SiCf/SiC) composites are important for manufacturing the hot-section components of aero engines and supersonic vehicles. Hence, quality control, as well as qualitative and quantitative non-destructive testing and evaluation (NDT&E) are critical. A grey (G) value method for the characterisation and NDT&E of manufacturing defects in SiCf/SiC composites based on the attenuation behaviour of low-energy X-rays was proposed, and a digital X-ray imaging detection system was developed. Specimens with artificial and manufacturing defects were evaluated, thereby revealing that imperfections were induced when the SiCf/SiC composites were formed at the high-temperatures; microcracks (100-μm-wide) and rectangular defects (0.1-mm-deep) were detected with a sensitivity exceeding 100 μm. Our results demonstrated that ‘voids’, ‘microcracks’, ‘porosity’, ‘polymer impregnation inhomogeneity’, ‘fibre-lack’, and ‘gap-delamination’ were the typical manufacturing defects caused during formation of SiCf/SiC composites at high temperatures; the minimum deviation between the detected and designed length of a 10-mm-long microcrack in the 3.0-mm-thick SiCf/SiC composite specimen was ~3%; the manufacturing defects were effectively characterised and evaluated using the distribution behaviours of G values and digital radiographic imaging features.

Integrated LTE and Millimeter-Wave 5G MIMO Antenna System for 4G/5G Wireless Terminals.

This work demonstrates an integrated multiple-input multiple-output (MIMO) antenna solution for Long Term Evolution (LTE) and Millimeter-Wave (mm-wave) 5G wireless communication services. The proposed structure is comprised of a two-element LTE MIMO antenna, and a four-element 5G MIMO configuration with rectangular and circular defects in the ground plane. For experimental validation, the proposed structure is fabricated on a Rogers RO4350B substrate with 0.76 mm thickness. The overall substrate dimensions are 75 mm × 110 mm. The proposed structure is capable of operating at 5.29–6.12 GHz (LTE 46 and 47 bands) and 26–29.5 GHz (5G mm-wave) frequency bands. Additionally, the measured peak gain of 5.13 and 9.53 dB is attained respectively for the microwave and mm-wave antennas. Furthermore, the analysis of the MIMO performance metrics demonstrates good characteristics, and excellent field correlation performance across the operating bands. Furthermore, the analysis of the Specific Absorption Rate (SAR) and Power Density (PD) at the lower frequency band (5.9 GHz) and PD only at mm-Wave frequency band (28 GHz) verifies that the proposed antenna system satisfies the international human safety standards. Therefore, the proposed integrated MIMO antenna configuration ascertains to be a potential contender for the forthcoming communication applications.

Experimental and simulation study of the effect of cut-out defect in carbon fibres twill weave composite

The automated fibre placement (AFP) is an effective manufacturing process that produces a large complex structure with high quality at low secondary waste. Although, the AFP is highly accurate and reproducible and very common in the aerospace application, break and cut-out defect in the plies are inevitable. In this study, we have investigated 4 different types of geometrical cut-out defect that have an equal area (38.4 mm2) that cut from identical locations in the specimen plies. The effect of triangular, rectangular, square and circular cut-out defect has been investigated and compared to a virgin material that has no flaw or cut-out defect in the plies. It has been observed and hence reported that the circle induced flaw has caused 73% reduction in the impact strength due its 360° distortion of carrying stress. The failure mode of the circular cut-out defect specimens was proven to be matrix crack due to miscarriage of the stresses in the fibre, while a pull-out fibres failure mode has been observed in the virgin specimen. The experimental work has been validated using FEA analysis that identically simulate the boundary condition of both bending and impact test.

Filtering magnetic relaxation mechanisms of YIG(001) thin films using ferromagnetic resonance

In this work we used the ferromagnetic resonance (FMR) technique to measure the contributions for the magnetic relaxation in Y3Fe5O12 textured films deposited onto (001) Gd3Ga5O12 by magnetron sputtering. Through the numerical fitting of the angular dependence of the in-plane FMR linewidth measurements we identified the contribution of the Gilbert, two-magnon and mosaicity relaxation mechanisms. Regarding to the line broadening due to two-magnon mechanism, we interpreted it as a result of rectangular defects distributed over the film plane. The overall defects were decomposed into three crystallography direction chosen according to the in-plane FMR resonance field experimental results. We observed the two-magnon scattering rate being relevant for YIG thickness below 150 nm. Although it is also present for thicker samples, the Gilbert mechanism dominates with mosaicity being very important to corroborate the shape of the angular dependence, but with small amplitude. We point out the relevance of our finding regarding two-magnon scattering effect in YIG thin films, directly impacting in an overestimation of the spin pumping contribution to the FMR line broadening in YIG/ heavy-metal systems.

Experimental Study on the Dynamic Behavior of Running Crack Affected by Defect Shape and Filling Material

Using the caustics method and the experimental system of digital laser dynamic caustics, the model experiment of drop hammer impact loading was carried out, and the effect of the defect shape (circular and rectangular) and the filling material (air, epoxy, and silicone rubber) on the propagation behavior of the running crack was investigated. The experimental results show that, under the impact loading, the running crack initiates at the end of precrack and propagates toward the defect. After the running crack connects to the defect, it accumulates energy within a certain period before initiating again at the upper edge of the defect. Subsequently, only one running crack is formed at the upper edge of the circular defect, but two running cracks are formed at the upper edge of the rectangular defect. The defect shape and the filling material have a significant effect not only on the energy accumulation time of the running crack at the defect but also on the stress intensity factor when initiating at the defect. The effect degree of the defect shape on the running crack propagation behavior is in the following order: circular defect > rectangular defect, whereas the effect degree of the filling material on the running crack propagation behavior follows this order: air > silicone rubber > epoxy.

Experimental study on enhancement of defect detection and defect size estimation in deep groove ball bearing

Rolling elements bearings are widely used in rotating equipment and machines to support load and to reduce friction. The presence of micron sized defects on the mating surfaces of the bearing components can lead to failure through passage of time. The large size defects on bearing elements can be detected/identified by time domain and frequency domain analysis of its vibration signals. However, it becomes difficult to detect local bearing defects at their initial stage either due to their smaller size or presence of noise. In the present experimental study, detection of local defects like crack and pits on bearing races have been carried out. Vibrations generated by healthy bearing and bearing having circular or rectangular defect on either race of bearing have been analyzed using MATLAB software. Signal to noise ratio of vibration signal has been enhanced through self- adaptive noise cancellation. Moreover, width of rectangular defects and diameter of circular defects have been estimated through ‘db5’ wavelet. The estimated defect sizes have been compared and validated through measured actual crack width or pit diameter. Accuracy of results proves that wavelet analysis of time domain signal can be used with confidence to estimate the width of fatigue crack and pit of the bearing races.

Análisis de la variación del flujo magnético alrededor de defectos rectangulares y triangulares en placas ferromagnéticas

El presente artículo, enmarcado en el contexto del proyecto Desarrollo de un sistema experto para el modelado y monitoreo de grietas superficiales (tipo triangular y rectangular) en tuberías ferromagnéticas usando el método de memoria magnética, presenta el análisis de la variación del flujo magnético alrededor de defectos rectangulares y triangulares en placas ferromagnéticas. Este análisis utiliza una metodología con un estudio exploratorio de modelos numéricos a partir de modelos analíticos existentes. Los modelos numéricos obtenidos servirán como base al compararlos con resultados experimentales para cuantificar la magnitud de los defectos. Los resultados determinaron, a través del análisis de datos, que es posible detectar y clasificar, con un alto grado de certidumbre y alto nivel de confiabilidad, el tamaño y la forma de los defectos superficiales tipo rectangular y triangular mediante los componentes tangencial y normal de esos defectos.

Surface circular-arc defects interacted by laser-generated Rayleigh wave

In this work, the finite element method (FEM) is used to investigate the propagation of laser-generated Rayleigh wave along the material surface at the quarter-arc transition surface under the thermoelastic regime, and to establish the relationship between the circular-arc radius and the time domain characteristics of reflected and transmitted Rayleigh waves. The simulation shows that the amplitude of the reflected Rayleigh wave decreases whereas the amplitude of the transmitted Rayleigh wave increases as the radius increases, which is significantly different from the well-studied interaction of Rayleigh waves with the perpendicular transition surface. By introducing the circular-arc defects which are easily formed in some engineering components during the material surface quenching, we find that the depth gauging of the surface circular-arc defects is more accurate in comparison to the surface rectangular defects based on the arrival time of the transmitted Rayleigh wave. This is further verified by the corresponding experimental results. These foundings are of practical values for detecting the depth of the arc defect quantitatively by the laser ultrasonic technique.

Circumferential SH Wave Piezoelectric Transducer System for Monitoring Corrosion-Like Defect in Large-Diameter Pipes.

The fundamental circumferential shear horizontal (CSH0) wave is of practical importance in monitoring corrosion defects in large-diameter pipes due to its virtually non-dispersive characteristics. However, so far, there have been limited CSH0 wave transducers which can be used to constitute a structural health monitoring (SHM) system for pipes. Moreover, the CSH0 wave’s capability of sizing the corrosion-like defect has not yet been confirmed by experiments. In this work, firstly, the mechanism of exciting CSH waves was analyzed. A method based on our previously developed bidirectional SH wave piezoelectric transducers was then proposed to excite the pure CSH0 mode and first order circumferential shear horizontal (CSH1) mode. Both finite element simulations and experiments show that the bidirectional transducer is capable of exciting pure CSH0 mode traveling in both circumferential directions of a 1-mm thick steel pipe from 100 to 300 kHz. Moreover, this transducer can also serve a sensor to detect CSH0 mode only by filtering circumferential Lamb waves over a wide frequency range from 100 to 450 kHz. After that, a method of sizing a rectangular notch defect by using CSH0 wave was proposed. Experiments on an 11-mm thick steel pipe show that the depth and circumferential extent of a notch can be accurately determined by using the proposed method. Finally, experiments were performed to investigate the reflection and transmission characteristics of CSH0 and CSH1 waves from notches with different depths. It was found that transmission coefficients of CSH0 mode decrease with the increasing of notch depth, which indicates that it is possible to monitor the depth change of corrosion defects by using CSH0 wave.

Finite element modeling of girth welded pipe with multiple defects

Due to the expansion of the pipeline network in the transportation of petroleum and its derivatives, it has been essentialto develop studies to evaluate and guarantee the safety condition, as well as the reliability of such facilities. Weldedpipelines have been widely used, and they are susceptible to corrosion. Since the heating at the welded point may leads tostructural and compositional modifications in the material, which may generate corrosion. The present paper presents anonlinear computational model burst pressure assessment in API X70 girth welded pipes with multiple defects, created bycorrosion, which may represent a great risk for gases and fuel leakage during transportation. In this study, the computationalmodel has been developed by the finite element method considering the isotropic hardening model and contact conditionsbetween different materials involved in the analysis, with corrosion simulated as a rectangular defect. The corroded pipe andthe efficiency of the computational model have been analyzed by varying the width of the heat-affected zone (HAZ), and thedepth of single and multiple defects. The results obtained by using the finite element analysis have been compared with thesemi-empirical methods and literature results. The computational model developed by the present work has presentedsatisfactory results.

Freshly Isolated Versus Culture Expanded Bone Marrow Stem Cells in Healing of Bony Defects in DOGS

Purpose this study was conducted between 2011 and 2017 at the faculty of Veterinary Medicine Cairo University and aimed to histologically and radiologically compare the efficiency of freshly isolated bone marrow mesenchymal stem cells (F-BMMSC) versus culture expanded bone marrow mesenchymal stem cells (E-BMMSC) when added to the mixture of autologous platelet rich fibrin (PRF), collagen with nano-hydroxyapatite in healing of critical bony mandibular defects in mandibular site in dogs. Material and methods 12 healthy adult Mongrel dogs were used in this study and bilateral rectangular full thickness mandibular inferior border critical bone defects (15X10 mm) just before the angle area were resected. Group A (The left side) contained: E-BMMSCs The expanded BMSC seeded on collagen sponge with Nano-Hydroxyapatite and PRF membrane. Group B (The right side) contained: F-BMMSCs The Gradient immediately separated BMSC seeded on collagen sponge with Nano-Hydroxyapatite and PRF membrane. Radiographic follow up was done immediate, 4, 8, 12 weeks Scarification was done 4, 8, 12 weeks postoperative. local bone mineral densities (BMD) were measured on a DXA system. Histological evaluation was done using H&E. Results the results showed that group B right defects had better healing results than group A right defects all over the follow-up period, but the differences were not statically significant. Conclusion the study findings indicate that The F-BMMSCs that seeded in nano-hydroxyapatite collagen type I n-HA-COL scaffolds combined with platelet rich fibrin PRF successfully repaired mandibular critical size defects, the same as the E-BMMSCs seeded in the same scaffold. .

Energetics of domain wall in magnetic nanowire

Micromagnetic modeling is used to study the energetics of magnetic switching of single-layer permalloy nanowire. The energy landscape of the system is studied using Nudged Elastic Band method. It has been shown that presence of rectangular shape defects on long side and inside nanowire leads to the appearance of local maxima and minima on the energy profile. Thus artificially created imperfections can be used for effective DW pinning.

Optical bistable switch based on the nonlinear Kerr effect of chalcogenide glass in a rectangular defect of a photonic crystal

An optical bistable switch based on a photonic crystal resonator using the nonlinear effect of a chalcogenide glass in a rectangular defect cavity is proposed and investigated numerically. The influences of the designed cavity and refractive index of the Kerr nonlinear medium on the transmission of the resonator are analyzed precisely through finite-difference time-domain simulation. The simulation results show that our compact structure possesses excellent switching characteristics by tuning the incident electric intensity. The properties of the optical bistability are investigated at the resonance wavelength with three different detuning parameters. In addition, the results show that this switch has a wide operating wavelength regime and fast operation speed of 90 Gb/s. Considering numerous characteristics, such a high-speed switch can find application for all-optical devices.

Imaging of Lamination Defect in Metallic Plate Based on Local Wavenumber Domain Analysis

In metallic plate structures, a lamination defect is a type of internal defect that is commonly generated in the manufacturing process, which is mostly parallel to the surface of the plate. This study presents a technique of imaging a lamination defect in a metallic plate by using Lamb waves based on the local wavenumber domain analysis method. Owing to the processing technique, an aluminum beam structure is utilized to represent the metallic plate for the detection of the lamination defect. A three-dimensional finite-element model of an aluminum beam with a rectangular lamination defect is constructed with MatLab and ABAQUS commercial software. The propagation characteristics of Lamb waves are discussed by analyzing the simulated wavefield. A complicated wave-propagation phenomenon of multiple reflection and transmission is observed between the interaction of Lamb waves and the lamination. By performing local wavenumber domain analysis on the wavefield, the wavenumber distribution is obtained, from which the location and profile of the lamination defect are identified. An experimental study is carried out to verify the numerical result. A fully non-contact detection system consisting of an electromagnetic acoustic transducer and laser ultrasonic inspection system is established to inspect the artificial machined beam structure. The experimental result is in good agreement with the numerical result.

Investigation of Rayleigh wave interaction with surface defects

The current article is concerned with the interaction of Rayleigh waves with surface defects of arbitrary shape in a homogeneous, isotropic, linearly elastic half-space. Using a linear superposition principle, the interaction generates a scattered field which is equivalent to the field radiated from a distribution of horizontal and vertical tractions on the surface of the defect. These tractions are equal in magnitude but opposite in sign to the corresponding tractions obtained from the incident wave. The scattered field is then computed as the superposition of the displacements radiated from the tractions at every point of the defect surface using the reciprocity theorem approach. The far-field vertical displacements are compared with calculations obtained by the boundary element method (BEM) for circular, rectangular, triangular and arbitrary-shaped defects. Comparisons between the theoretical and BEM results, which are graphically displayed, are in excellent agreement. It is also discussed the limitations of the proposed approximate theory.
 Keywords:
 half-space; Rayleigh wave; surface defect; reciprocity theorem; boundary element method (BEM).