Circular Bend Research Articles

Research on localization control of magneto-controlled capsule endoscopy based on sensor array

Purpose To improve the localization accuracy of the magnetically controlled capsule endoscope (MCCE), a new localization method, based on the magnetic dipole model, is proposed, where the anti-disturbance permanent magnet (APM) is used as the source of stable magnetic field, thus reducing the interference of the geomagnetic field or the electric conductor magnetic field in the system. Design/methodology/approach The coupling magnetic force model between the APM and the capsule endoscope is established to obtain the magnetic force relationship and magnetic induction intensity. Along the three axes, magnetic induction intensity data are collected by a 3 × 3 sensor array composed of nine magnetic field intensity sensors, while the data are uploaded to the main computer by the STM32F103C8T6 control board over a ESP8266 WIFI module connection. Next, the axial magnetic induction intensity data are decoupled to obtain the measurement trajectory, whereas the error function is established based on the calculated trajectory parameters. Finally, the Levenberg–Marquardt (L-M) algorithm is used to solve the position information of the MCCE. Findings Experiments show that the average localization error of an MCCE in a straight and circular bend tube is 4.76 mm, whereas in a U-bend tube, it is 6.82 mm. Originality/value The optimized simulation value in the linear and bending environment is in good agreement with the experimental value, which verifies the accuracy of the MCCE localization system based on magnetic field sensor array, exhibiting good performance in localization and position tracking while providing a theoretical basis for the subsequent research.

Pressure Drop Analysis of Turbine Housing Model with Circular Sliced Pipe for Micro Hydropower Generation

Energy independence is a government program aiming to meet society's energy needs evenly. Steps to increase energy independence in the new and renewable energy sector include hydro-energy generation. One of the important components of a hydro generator is the penstock pipe and turbine housing, which channels water and then pushes and drives (spins) the turbine with the flow of water to produce electrical energy. The turbine housing flow design innovation must provide a function as an optimal fluid conductor by minimizing the resistance that occurs when fluid flows towards the turbine housing and rotates the turbine optimally. The scope of this research includes analysis of the phenomenon of energy loss flowing in circular pipe slices in hydroelectric power plant turbine housings with influencing factors such as friction, turbulence, and flow resistance, as well as measuring the pressure drop in circular pipe slices. The model developed is a circular slice bend with angles of 180 degrees, 270 degrees, 360 degrees, and 450 degrees, taking into account the optimal curvature ratio (R/D) of 3.5. Based on previous research, 90-degree wedge bends with many slices (n_(90-degree)) 4 to 6 or  4 and pressure drop coefficient (C_(pd-th)) obtained 180-degree (0.333 – 0.200), 270-degree (0.445 – 0.277), 360-degree (0.527¬ – 0.339), 450-degree (0.587 – 0.390) with a bend length L, an elevation reduction angle  and a 1.5D upstream-downstream elevation difference to avoid contact between the upstream and downstream bends. The results obtained from this research are the slice modules that can be used and the resistance coefficient values that arise from the slice modules. The more slices selected according to the angle of inclination chosen, the smoother the resulting circular bend shape and the lower the resistance value, but the work will be more difficult. The most optimal slice module is the number of slices that allow its implementation, and the resistance coefficient is small. By knowing the optimal resistance coefficient value, the resulting pressure drop can be predicted to maximize the thrust to rotate the turbine.

Observing Deformation‐Induced Backscattering in Flexible Valley‐Hall Topological Metasurfaces

AbstractTopological metasurfaces based on the quantum valley Hall effect have garnered attention for their ability to enable novel physical phenomena. However, the propagation characteristics of flexible topological metasurfaces under bending and folding remain underexplored, leaving open questions about the behaviors of topological edge states in these configurations. This study investigates edge‐state propagation and frequency response in topological insulator metasurfaces under varying degrees of circular bending and dihedral folding. A flexible topological insulator is designed, fabricated, and tested with a passband between 4.4 and −4.6 GHz, monitoring how its transmission passband changes as the curvature radius decreases from 400 to 100 mm. Simulations and experimental measurements reveal how the transmission frequency response and near‐field distribution evolve as the metasurface undergoes folding from 90° to 30°. Results show that both the topological passband and transmission gradually vary with reduced folding angles, while arc‐shaped bending minimally affects the propagation path, though the passband narrows slightly with increased curvature. To illustrate the impact, metasurface communication performance between planar and folded configurations (90° to 30°) is compared, observing a notable performance drop after folding. This study aims to enhance the understanding of edge‐state properties in topological systems under deformation and promote further advancements in flexible topological devices.

Effect of size and anisotropy on fracture process zone of coal: An experiment and numerical simulation

The size and properties of the fracture process zone (FPZ) have a significant impact on the fracture toughness of materials. Researching and understanding the characteristics of FPZ contribute to optimizing material performance and enhancing the reliability of engineering structures. In this study, the newly proposed modified semi circular bending (SCB) test method was used to carry out the pure mode I fracture test of coal samples with four sizes and four bedding angles, the development process of FPZ was obtained by using digital image correlation method, and the cohesive zone model considering the bedding plane was established. The influence of size and anisotropy on the development and size of FPZ was studied, and the influence mechanism of FPZ on the size effect and anisotropy of fracture toughness was revealed. The results show that the FPZ length of coal has obvious size effect and anisotropy. The FPZ length increases with the increasing specimen size, and increases first and then decreases with the increasing bedding angle. The FPZ relative length decreases with increasing specimen size, indicating that as the specimen size increases, the influence of specimen boundaries on PFZ gradually decreases, and the size effect of fracture toughness also gradually weakens. The competition between microcrack development driven by principal stress and microcrack development driven by bedding plane results in anisotropy in the development process of FPZ. The anisotropy of FPZ development process results in the anisotropy of FPZ length, fracture toughness and crack propagation path. The research findings can provide valuable guidance for the design of hydraulic fracturing in coal seams.

A low loss silicon waveguide bend based on width and curvature variations

A simple, low loss and compact 90° SOI waveguide bend constructed by using an inner circular curve and an outer Euler-circular curve was proposed, optimal designed and fabricated. By adopting this simple structure, the width and curvature of the waveguide bend can be varied simultaneously, which can effectively suppress both the mode mismatch loss and the radiation loss. Three-dimensional finite difference time domain simulation results indicate a very low excess loss of about 0.0056 dB can be achieved for equivalent bending radius of 2 μm. By using the cut-back method, a low loss of about 0.0175 dB at 1550 nm was measured, which is less than one quarter of the traditional circular bend. In addition, the wavelength dependence for the proposed SOI waveguide bend was investigated and 0.0088 dB–0.0247 dB was measured in the wavelength range of 1480∼1580 nm.

A CFD Study of Particulate Deposition on Dimple-Type Flue Walls of Coal-Fired Power Plants

The study of particle deposition in bends is always a continuous challenge in various engineering and industrial applications. New types of channels with special microstructures on the surfaces can be effective in modifying the flow field structure as well as particle deposition in channels. In this study, a 90° circular bend with a convex dimple structure was used, and the flow field and the deposition of particles in the channel were analyzed; the Stokes numbers (St) used were 0.016, 0.355 and 1.397. The reliability of the model was ensured by mesh-independence validation as well as speed validation. In a 90° bend channel with convex dimples, the temperature distribution, particle deposition distribution, flow structure and secondary flow were examined. The effects of the number of convex dimples and St in the bend on the flow field structure and particle deposition characteristics were analyzed. The results show that the main factors affecting the deposition characteristics of particles in bends are St, gravitational deposition, thermophoretic force, turbulent vortex clusters and secondary flow distribution. The effect of St is more pronounced, with the deposition rate increasing as the St increases, and the deposition location of the particles is mainly clustered on the outside of the bend structure of the elbow.

Field performance validation of the Louisiana balanced asphalt mix design framework

The balanced mix design (BMD) approach was implemented by agencies to complement the volumetric mix design method. The BMD approach addresses typical pavement distresses using mechanical tests. This study aimed to validate the Hamburg Wheel Track (HWT) rut depth and Semi Circular Bend (SCB) critical strain-energy release rate (Jc) thresholds specified in the Louisiana BMD framework. Seven field projects, including 13 pavement sections with 8–18 service years, were evaluated. Field distress data showed that the maximum HWT rut depth and minimum SCB Jc thresholds are effective parameters for assessing rutting and cracking performance, respectively.

Numerical analysis of natural convection in a porous circular bend

The study of natural convection in porous circular bends is pivotal due to its applications in various cooling system designs. This paper focuses on a circular bend with a heated inner wall and a colder outer wall, employing the finite difference method to solve the governing equations. The research encompasses Rayleigh numbers ranging from 20 to 750 and an aspect ratio (defined as R=R2−R1R1) from 1.0 to 2.0. The findings highlight that variations in Rayleigh numbers and the circle’s radius significantly enhance heat transfer rates via convection, underscoring their critical roles in influencing flow and heat transfer within this configuration. It is also observed that theNuAvg on the heated wall increase with the increase in R. It is observed that for R = 0.75, NuAvg is 8.8 and for R = 1.5, NuAvg is increase to 9.7.

A high-power ultrasonic transducer operated in MHz range by circular plate bending mode using a single parabolic reflector

This research developed a HF, high-power ultrasonic transducer. Operating at 1.54 MHz, the transducer generated plane waves through the excitation of the thickness mode of a piezoelectric ring. These waves are subsequently focused by a parabolic reflector, exciting the bending mode of a circular plate and yielding substantial mechanical output at the center. Under a driving voltage of 48 Vpp, the transducer achieved a saturation velocity of 11.7 mpp/s. The mechanical quality factor ( Qm ) of the resonant mode is calculated using the half-power bandwidth method, resulting in a value of approximately 1250. The proposed transducer exhibits outstanding performance and holds promising applications in the fields of biology, medicine, and sonochemistry.

Investigation of dynamic three–point bending fracture properties of SCB sandstone

The stress intensity factor (SIF) is not only an important parameter in the field of fracture mechanics but also a key indicator reflecting the strength of the stress field at the crack tip. Therefore, this paper uses the Split–Hopkinson–Pressure–Bar (SHPB) device to conduct dynamic fracture experiments on semi–circular bend (SCB) sandstones of different fracture modes and then uses an experimental–numerical method to simulate the dynamic loading process to explore the changes law in SIF. Finally, combined with the high–speed digital image correlation (HS–DIC) technology, the fracture characteristics of SCB sandstones are studied. The results show that the rising rate of dissipated energy acting on the specimen fracture and damage increases rapidly when it is close to dynamic fracture, which makes the dynamic SIF also get a substantial increase, and the influence of dissipated energy on dynamic SIF is seen to be very strong. Moreover, prior to the occurrence of dynamic initiation fracture, the damage to the specimen is primarily triggered by microscopic tensile effects at the tip of the preset crack, which results in the value of KI always being greater than KII before the dynamic fracture occurs. Meanwhile, the distribution curve of dynamic SIF exhibits better symmetry or a trend towards symmetry compared to the distribution curve of static SIF. This suggests that the tip of the preset crack distributes with more uniform tensile and shear stresses during dynamic loading. Using the HS–DIC technique, when the specimen occurs dynamic pure mode I initiation fracture, there was a good symmetrical trend in both the vertical strain around the fracture crack and the horizontal displacement field at the specimen. However, when specimens occur dynamic mixed mode I/II initiation fracture, the horizontal displacement fields showed asymmetry, and the specimens all suffered varying degrees of shear damage.

On the mixed mode fracture of DLP manufactured SCB specimens

The scope of this study is to investigate the mixed mode fracture of components manufactured from photo-polymerized resin using the Digital Light Processing (DLP) additive manufacturing technology.The mixed mode tests were performed on Semi Circular Bend (SCB) specimens loaded under symmetric Mode I, asymmetric mixed mode and mode II loading, respectively. The specimens manufactured via DLP have a crack introduced during the manufacturing process. Tests were performed at room temperature using a universal testing machine with three point bending grips at a constant loading speed. Four tests were carried on for each supports position.The experimental results expressed as KII/KIC versus KI/KIC are plotted by adopting four fracture criteria, namely the Maximum Tensile Stress (MTS), the Strain Energy Density (SED), the Maximum Energy Release Rate (Gmax), and the Equivalent Stress Intensity Factor (ESIF). Most of the experimental results fall in the range of fracture envelope curves.

DETERMINATION OF CHARACTERISTICS OF FATIGUE CRACKS GROWTH IN THE AXLES OF RAILWAY CARRIAGES

Providing damage resistance is the most important requirement presented to railway axles. This paper provides a detailed review of the characteristics of resistance to fatigue crack growth in axles made of EA4T steel (25CrMo4). This steel is typical for axles of high-speed rolling stock. Resistance to fatigue crack growth is defined by the nature of the Paris-Erdogan curve da/dN=CKm, the parameters of which are the coefficient C and the exponent m. Determination of these parameters is based on the results of fatigue tests with the samples or with full-scale axles having cracks. The analysis of numerous scientific papers has shown that for the specified steel there is a significant scatter in the values of these parameters. This scatter is caused by a number of factors, the main of which are: the difference in test objects (from small samples of the SE(B) type to full-scale rolling axles 190 mm in diameter); the difference in loading methods (tension-compression, flat bending, circular bending); the variation of mechanical properties of EA4T steel. In the paper the models of surface fatigue crack geometry are analyzed and semi-elliptical shape of crack front line is selected as the most acceptable. The significant scatter in the values of the parameters m and C prevents to establish reliably the residual life of axles with cracks, which is an important characteristic for practical forecasting of axle survivability. The technique for parameters m and C optimization in view of semi-elliptical shape of the crack front line has been developed. The relationship linking the parameters m and C has been established. The method for determining the residual life of the axle by the criterion of non-destruction is proposed. The dependence between the residual life and the value of the parameters of the Paris-Erdogan equation in the development of fatigue failure is established. The procedure for axles monitoring timeframes setting to prevent their fatigue failure is discussed. Keywords: parameters of Paris-Erdogan equation, fatigue crack, residual life of axle.

Pavement design using bituminous surface course with recycled aggregates

The utilization of Recycled Aggregates (RA) in the construction of pavement structure is one of the inventive and eco-friendly construction techniques. This scale down the construction cost without negotiates the strength and the durability of the pavement structures. However, RA is rigid in nature because it is obtained from aged bituminous mixtures to enhance a rejuvenator is usually added in order to lower the stiffness. Rejuvenator surges the utility of the bituminous mixtures and makes them be smoothly paved and compacted. The objective of this study is to design a flexible pavement structure using Stone Matrix Asphalt (SMA) as a surface course in order with RA. In SMA mixture major component is occupied by coarse aggregates, mineral filler, bitumen and a minor component of fine aggregates helps to fill the voids present in coarse aggregate which gives stone-on-stone contact. The bitumen binder and mineral filler form mastic, providing durability to the mixture. In this study, the performance of SMA mixtures with different RA proportions and a rejuvenator will be compared with conventional SMA mixture with zero percentage RA. Marshall Mix design is outlined to find the Marshall and volumetric properties of SMA mixtures and to regulate the Optimum Binder Content (OBC). The mixtures will be compared based on the drain down, stripping, Indirect Tensile strength (ITS) and Semi circular bend (SCB) test results. The analysis and design of flexible pavement structure using the prepared SMA mixtures with different RA contents as surface courses also will be carried out as a component of the study.SMA mixture of 40% replacing RA with 3% of palm sludge oil as rejuvenator exhibits optimum bitumen content where vertical stress, strain and displacement obtain reduction with compared to IRC 37 conventional SMA mixture.

Numerical Investigations of Turbulent Flow Through A 90-Degree Pipe Bend And Honeycomb Straightener

Abstract Pipe bends are commonly used in piping systems in offshore and subsea installations. The present study explores the design considerations for the honeycomb straightener inserted downstream of a 90-degree pipe bend. The objective of the study is to evaluate the effectiveness of the honeycomb in suppressing the flow swirling for different distances from the bend outlet (Lb) and different values of the honeycomb thickness (t). The turbulent flow through the 90-degree circular pipe bend with the honeycomb straightener is investigated by carrying out numerical simulations using the Reynolds-Averaged Navier-Stokes (RANS) turbulence modeling approach. The Explicit Algebraic Reynolds Stress Model (EARSM) is adopted to resolve the Reynolds stresses. The honeycomb thickness to pipe diameter ratio (t/D) is varied between 0.1 and 1. The normalized distance from the bend outlet to the honeycomb straightener (Lb/D) is varied between 1 and 5. The disturbance in the velocity field is generated by the pipe bend with the curvature radius to pipe diameter ratio (Rc/D) of 2 and Reynolds number (Re) of 2×105. It is found that both the increase in Lb/D and t/D improves the performance of the device in removing the swirl behind the bend outlet. The best performance is observed for the honeycomb straightener with the distance Lb/D=5 and thickness t/D=0.5.

Introduction of calcium lignosulfonate to delay aging in bituminous mixtures

This study examines the merits of using calcium lignosulfonate (CLS) to mitigate negative effect of aging on bituminous mixtures. To do so, we studied how fracture energy and fracture toughness of the bituminous mixtures containing CLS change when exposed to long-term aging. Aging is implicated in premature cracking including but not limited to top-down cracks and low-temperature cracks which negatively impact road roughness, and subsequently ride quality and driver safety. Considering that latter cracks are induced by tensile and shear forces, we used semi circular bending (SCB) test to quantify fracture energy and fracture toughness of mixtures containing 5–20% CLS under both mode I and II. Each mixture was exposed to short and long term aging and tested at temperature of +15 °C and −15 °C. The study results showed that introduction of CLS increased the fracture energy and fracture toughness of the mixtures under both modes I and II. The study outcomes provides insights for advancing socioeconomics of pavements by mitigating surface cracks which in turn enhances the driver safety, ride quality and maintenance cost of pavements.

Numerical Synthesis of the Dual Frequency 28/35 GHz Power Monitor in the 160° Circular Miter Bend

A numerical method of the synthesis of the array pattern for the linear holes coupler embedded on the miter bend is proposed in this article. This method allows pattern control with the arbitrary incident angle when the waveguide operates at dual frequency. Combined with the analysis method, an algorithm has been developed for synthesizing the antenna pattern. As an example, a power monitor has been designed for a 28/35 GHz waveguide with an incident angle of 55°. An arrangement of the holes array has been obtained to get the desired array pattern at a given angle, and the directivity of the power monitor is larger than 40 dB at 28/35 GHz.

Low-loss, ultracompact n-adjustable waveguide bends for photonic integrated circuits.

Countless waveguides have been designed based on four basic bends: circular bend, sine/cosine bend, Euler bend (developed in 1744) and Bezier bend (developed in 1962). This paper proposes an n-adjustable (NA) bend, which has superior properties compared to other basic bends. Simulations and experiments indicate that the NA bends can show lower losses than other basic bends by adjusting n values. The circular bend and Euler bend are special cases of the proposed NA bend as n equals 0 and 1, respectively. The proposed bend are promising candidates for low-loss compact photonic integrated circuits.

Finite element analysis of deformation behaviour of circular sheet during laser forming process

Laser forming of sheet metal involves inducing a bending process through the application of thermal stress using a defocused laser source. In laser forming the formation of bowl-shaped shapes requires the input of various laser process parameters. In this study, we investigate the thermo-mechanical deformation behaviour of a circular plate subjected to laser irradiation scanning. To analyse this phenomenon, we employ the Finite Element Method (FEM) with the aid of the software ABAQUS 6.10. The moving laser heat source is modelled as Gaussian heat flux, and DFLUX subroutine is written in FORTRAN. The work piece material AH36 is considered. The Finite Element Method (FEM) proposed model is verified against experimental results. Additionally, a parametric study has been conducted to assess the impact of laser process parameters on the temperature distribution of AH 36 material. The temperature distribution is noted to rise with an increase in laser power. However, as the scanning speed and laser beam diameter of the circular laser heat source increase, both temperature and bend angle exhibit a continuous decrease. Further, it is found the plastic strain is measured along the laser irradiation path, therefore the averaged material properties are not altered of the dome shaped obtained by laser forming. Based on the parametric studies, the optimum laser process parameters are also determined to get the dome shaped of the circular sheet.

Regarding at the Circular Plates Rigidity with Radial Ribs, Neglecting the Welding Seams Influence. Ribs with Constant Thickness and Lineal Variable Heighness on Length, Placed Just on a Face

Abstract On base of obtained results in working [1], in a certain case one should take account the lineal chamfering of ribs upon the neutral fiber position and of the circular and plane plate bending rigiditybwith radial ribs. The illustration of the theoretical resultss is achieved on a given case.

Evaluation of the significance of different mix design variables on asphalt mixtures’ cracking performance measured by laboratory performance tests

Cracking is one of the primary distresses for asphalt pavements. This study is motivated to investigate the significance of the various mix design variables in determining the cracking performance of asphalt mixtures including both intermediate and thermal cracking performance, contributing to a better understanding of the mix design to improve the mixture cracking performance and promoting the development and implementation of the performance related specification and performance based specification. Total 20 mixtures were tested and evaluated in this study. The most current state of the practice mixture performance tests, including the Complex Modulus (E*) test, Semi Circular Bending (SCB) test, Disk Shaped Compact Tension (DCT) test and Direct Tension Cyclic Fatigue (DTCF) test were conducted on these mixtures for characterization of their cracking performance. The advanced statistical analysis methods were employed on the generated data base to investigate the significance of the mix design variables on determining the cracking performance parameters measured from the laboratory tests. The correlations between the various cracking performance parameters measured from the tests were also evaluated in this study. The results show that the binder related mix variables play the significant role for determining both the low temperature and durability cracking performance of asphalt mixture. For evaluation of the mixture fatigue cracking performance, several aggregate related variables in addition to binder variables are identified as the significant factors. Correlation analysis shows that mixture rheological based cracking parameter G-Rm does not show the strong correlations with neither the facture indices measured from the DCT and SCB tests nor the fatigue parameters measured from the DTCF test. This study also develops a simplified linear regression model as a predesign tool for evaluation and prediction of mixture cracking performance in general.