Right-angle Bend Research Articles

Design and demonstration of an acoustic right-angle bend.

In this paper, a broadband acoustic right-angle bend device in air is designed, fabricated and experimentally characterized. Perforated panels with various hole-sizes are used to construct the bend structure. Both the simulated and experimental results verify that the acoustic beam can be rotated effectively through the acoustic bend in a wide frequency range. This model may have potential applications in some areas such as sound absorption and acoustic detection in elbow pipes.

Microstructure evolution and properties of Cu-Cr alloy during continuous extrusion process

The microstructure evolution and properties of a typical precipitation strengthened Cu-0.82Cr alloy during continuous extrusion were investigated by means of optical microscopy, transmission electron microscopy, hardness and conductivity measurement. The severe plastic deformation and precipitation behavior of the alloy during deformation were discussed in detail. The results showed that hardness increased firstly until reaching the maximum value of 148 HB in right-angle bending, and then decreased in the extending extrusion zone. Severe deformation and precipitation process occurred during continuous extrusion, and the nano-scale precipitates inhibited the recrystallization in some extent, both of which contributed to the properties of the extruded alloy. The extruded alloy had an average grain size of about 1.5 μm, and it reached a yield strength, ultra-strength, elongation and electrical conductivity of 292 MPa, 346 MPa, 34% and 77.5%IACS, respectively.

Microstructure evolution of Al–Sr master alloy during continuous extrusion

The microstructure evolution of Al–Sr master alloy during continuous extrusion was investigated using X-ray diffractometer, scanning electron microscope and transmission electron microscope. Results indicate that the continuous extrusion process could change the Al4Sr particles of the alloy significantly in size and morphology. The as-cast needle-like Al4Sr particles are broken into small blocks in upsetting zone and crushed heavily in adhesion zone. Plenty of dislocations get tangled up in right-angle bending zone. Al4Sr particles grow in the extending zone. Finally, Al4Sr particles in products are approximately 28 μm in length. Al2Sr particles precipitate during the process. Compared with products by horizontal extrusion, Al4Sr particles by continuous extrusion are finer and distribute more evenly.

Effect of Billet Preheating Temperature on Continuous Extrusion Forming of Al-Sr Alloy

Abstract Based on numerical simulation and process experiment, this study investigates the effect of billet preheating temperature on continuous extrusion forming of Al-Sr alloy and the microstructure and mechanical properties of products. The numerical simulation results show that the temperature starts to rise after the billet enters into the cavity during the continuous extrusion of Al-Sr alloy, and the maximum temperature appears at the die exit. Moreover, the maximum equivalent stress appears in the right-angle bending zone. The billet preheating temperature increases from 300 °C to 480 °C, the maximum temperature of billet in cavity increases from 483 °C to 512 °C and the temperature at the die exit increases from 493 °C to 522 °C. The experiment results show that the Al4Sr phase morphology in products changes from granular to blocky and increases in size. The tensile strength decreases from 114 MPa to 104 MPa, and the elongation increases from 8.4% to 10.5%.

Mode Matching Analysis of an E-Plane $90^{\circ }$ Bend With a Square Step in Parallel-Plate Waveguide

We present a numerical model for the analysis of an E-plane right-angle bend in parallel-plate waveguide (PPW), with a single square step for matching purposes. This design can achieve wideband matching and can be implemented using hollow waveguides as well as multilayer printed circuit boards. An even-and odd-mode analysis is performed exploiting the symmetry of the structure. Two auxiliary problems are defined considering the bisecting plane of the bend as a perfect electric conductor or a perfect magnetic conductor, respectively. They are solved using a mode matching method. The mathematical derivations are discussed in detail. The proposed procedure can be embedded in efficient tools for the analysis of complex PPW systems, such as feed networks for antenna arrays.

Mathematical Modelling of Sound Radiation from a T Junction of City Roads in Windy Conditions

Abstract The sound radiation from vehicles travelling on the city roads with T junction was considered. The wind effect on acoustic field was taken into account. The solution of this problem was found with the help of the integral Fourier transforms and stationary phase method as the superposition of solutions for the cases of vehicles moving along the straight roads and roads with right-angle bend. As an example, the numerical analysis of traffic noise characteristics was carried out for the T junction city road on one of streets in the town of Łodź (Poland).

Microstructure evolution of Cu–0.2Mg alloy during continuous extrusion process

Abstract

DESIGN OF A BROADBAND RIGHT-ANGLED BEND USING TRANSFORMATION OPTICS

A right-angled waveguide bend using conformal transformation optics is proposed which guides the input electromagnetic wave smoothly through the waveguide, reduces the reflections and broadens the bandwidth of the device significantly. The isotropic material parameters are obtained through solving Laplace's equations with Dirichlet and Neumann boundary conditions. It is shown that the performance of the proposed bend is mainly determined by refractive indices lower than one. Utilizing this, the approximated resulting medium is implemented by drilling hole arrays in a dielectric background. In order to take advantage of planar technology, it can be implemented in a substrate integrated waveguide.

Common-Mode Noise Reduction Using Asymmetric Coupled Line With SMD Capacitor

In this paper, a bended differential transmission line using the asymmetric coupled line (ACL) with surface mount device (SMD) capacitor is proposed to suppress the common-mode noise. The bended differential transmission line using the ACL with SMD capacitor can greatly reduce the mode conversion from -6.91 to -13.29 dB and the Time-Domain-Through common-mode noise from 0.063 to 0.023 V as compared with the bended differential transmission line using the right-angle bend. Also, the differential-mode transmission is increased and the small differential-mode reflection is maintained. To verify the simulation results, measurement is done in the frequency and time domains where the measurement results are in good agreement with the simulation results.

Smoothed particle hydrodynamics simulations of flow separation at bends

The separated flow in two-dimensional bends is numerically simulated for a right-angled bend with different ratios of the channel widths and for a symmetric bend with different turning angles. Unlike the potential flow solutions that have several restrictive assumptions, the Euler equations are directly solved herein by the smoothed particle hydrodynamics (SPH) method, which is a Lagrangian approach without a mesh. The coefficient of flow contraction is obtained in terms of the ratio of the channel widths and the turning angle. The velocity field and pressure distribution in a right-angled bend are calculated. The shape of the free streamlines for a symmetric bend with several turning angles is obtained. The numerical steady-state results are validated against available theoretical solutions. The computed velocity on the free streamline is consistent with Kirchhoff’s theory.

Reciprocity in the scattering coefficients of acoustic waveguide modes

In this Letter, a proof is provided for the reciprocity between modal scattering coefficients of the acoustic waveguides connected by a junction enclosure. The result holds for all waveguide modes and for junction enclosures with locally reactive boundary conditions away from the interfaces between the junction and waveguides. Also provided is a physical interpretation of the reciprocity of the modal scattering coefficients. The scattering of two-dimensional waveguide modes by a right-angled bend in a rectangular duct is used as an illustrating example.

Determination of the complex acoustic scattering matrix of a right-angled duct

A method for determining the complete higher-order scattering matrix of an acoustic discontinuity is developed. The method is demonstrated for a right-angled waveguide bend, and the magnitude and phase of the reflection and transmission coefficients are extracted precisely. The procedure is straightforward and based on the solutions to the Helmholtz equation by the finite element method (FEM). The consistency of the scattering coefficients found by this method is verified by their properties of symmetry, and their accuracy is established by the conservation of energy. The reliability of the new technique is further proved by means of an arbitrary sound source and by comparing the direct FEM response to the reflection matrix calculation. Some features of the scattering matrix as a function of frequency are surprising, such as the steps and reversion of the phase evolution or the complete loss of transmission of the incoming wave. The methodology detailed in this paper can be extended to other multiport junctions, such as T-junctions or size discontinuities in ducts.

Corner cuts are close to optimal: From solid grids to polygons and back

We study the solution quality for min-cut problems on graphs when restricting the shapes of the allowed cuts. In particular we are interested in min-cut problems with additional size constraints on the parts being cut out from the graph. Such problems include the bisection problem, the separator problem, or the sparsest cut problem. We therefore aim at cutting out a given number m of vertices from a graph using as few edges as possible. We consider this problem on solid grid graphs, which are finite, connected subgraphs of the infinite two-dimensional grid that do not have holes. Our interest is in the tradeoff between the simplicity of the cut shapes and their solution quality: we study corner cuts in which each cut has at most one right-angled bend. We prove that optimum corner cuts get us arbitrarily close to a cut-out part of size m, and that this limitation makes us lose only a constant factor in the quality of the solution. We obtain our result by a thorough study of cuts in polygons and the effect of limiting these to corner cuts.

Bended Differential Transmission Line Using Compensation Inductance for Common-Mode Noise Suppression

In this paper, a bended differential transmission line using a compensation inductance is proposed to efficiently suppress the common-mode noise. The bended differential transmission line using the compensation inductance can then be implemented by the bended differential transmission line using the short-circuited coupled line. It has been shown that the bended differential transmission line using the short-circuited coupled line can greatly reduce the mode conversion from -5.47 to -14.75 dB, and the time-domain-through common-mode noise from 0.068 to 0.02 V as compared with the bended differential transmission line using the right-angle bend. In order to verify the simulation results, measurement is done in the frequency and time domains where the measurement results are in good agreement with the simulation results.

Microstrip discontinuity compensation using DGS

A novel compensation method for right-angled bend, T-junction, and cross-junction is presented. This method uses defected ground structures (DGS) to accomplish the compensation task. Special design graphs are provided to ease further designs. Three prototypes are designed and fabricated. The simulation and measurement results are in good agreement. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.

A comparison of outlet boundary treatments for prevention of backflow divergence with relevance to blood flow simulations

Simulation divergence due to backflow is a common, but not fully addressed, problem in three-dimensional simulations of blood flow in the large vessels. Because backflow is a naturally occurring physiologic phenomenon, careful treatment is necessary to realistically model backflow without artificially altering the local flow dynamics. In this study, we quantitatively compare three available methods for treatment of outlets to prevent backflow divergence in finite element Navier---Stokes solvers. The methods examined are (1) adding a stabilization term to the boundary nodes formulation, (2) constraining the velocity to be normal to the outlet, and (3) using Lagrange multipliers to constrain the velocity profile at all or some of the outlets. A modification to the stabilization method is also discussed. Three model problems, a short and long cylinder with an expansion, a right-angle bend, and a patient-specific aorta model, are used to evaluate and quantitatively compare these methods. Detailed comparisons are made to evaluate robustness, stability characteristics, impact on local and global flow physics, computational cost, implementation effort, and ease-of-use. The results show that the stabilization method offers a promising alternative to previous methods, with reduced effect on both local and global hemodynamics, improved stability, little-to-no increase in computational cost, and elimination of the need for tunable parameters.

Polymer waveguide delay device using right-angle X junctions

A four-channels polymer waveguide delay device is demonstrated and fabricated using direct ultra-violet photolithography process. The device is composed of right-angle junctions and bending waveguide. The optimized structural properties of the device and fabrication procedures are demonstrated. The loss of bending waveguides and right-angle X junction is calculated. The near-infrared field guided-mode patterns of the devices are obtained. Each incoming radio-frequency signal can be independently received. Measured delays are 0, 60.9, 121.9, and 182.9 ps. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26050

Moulding the flow of surface plasmons using conformal and quasiconformal mappings

In this paper, we analyze how transformation optics recipes can be applied to control the flow of surface plasmons on metal–dielectric interfaces. We study in detail five different examples: a cylindrical cloak, a beam shifter, a right-angle bend, a lens and a ground-plane cloak. First, we demonstrate that only the modification of the electric permittivity and magnetic permeability in the dielectric side can lead to almost perfect functionalities for surface plasmons. We also show that, thanks to the quasi two-dimensional (2D) character of surface plasmons and their inherent polarization, applying conformal and quasiconformal mapping techniques allows one to design plasmonic devices in which only the isotropic refractive index of the dielectric film needs to be engineered.

Effects of Continuous Extrusion on Microstructure Evolution and Property Characteristics of Brass Alloy

The continuous extrusion process would refine the microstructure effectively and increase the formability and properties of extrusion products, without preheating and post-mechanical treatment. During the continuous extrusion operation the microstructure of brass alloy significantly influences formability and properties. So the microstructure evolution rules of brass alloy during the whole continuous extrusion process were analyzed, and the hardness changing laws of the extruded brass alloy were also researched in this paper. By observing the microstructure evolution at different regions, the evolution rules of microstructure and properties of the continuous extrusion brass alloy were obtained. It was found that the dynamic recrystallization occurred at the right-angle bending region, which was proved by the hardness evolution of the extruded brass alloy. Therefore, it is feasible to control the properties of the extruded products by concentrating the right-angle bending region. This work gives the researching foundation of low formability materials based on continuous extrusion operation.

Micromachined 300-GHz SU-8-Based Slotted Waveguide Antenna

A micromachined 300-GHz slotted waveguide antenna is demonstrated using a simple fabrication technique based on metal-coated SU-8 thick resist. The antenna is designed to be built from a four-layer structure of equal layer thickness. It is fully characterized, and the measured radiation patterns show excellent agreement with the simulation. An H-plane matched right-angle bend is integrated in the antenna in order to achieve reliable and accurate connection with standard waveguide flange. The micromachined antenna is directional and low-profile and may find applications in low-cost sensors and radars.