Circle Hole Research Articles

Effect of hole diameter of rotary-shaped artificial reef on flow field

Opening holes, especially circular hole, in artificial reef block is a conventional choice in design of artificial reef. However, there is less scientific study about how to select the hole diameter. In this article the performance of the rotary-shaped artificial reefs with different size of circle holes was investigated using CFD method and the orthogonal experiment design. The reef having the best performance was identified. The results indicate that the design of interlaced hole diameter can significantly promote the flow field scope, especially the height of upwelling, in comparison with that with the uniform hole diameter. There is no obvious relationship between the cut-opening ratio and flow field effect for the rotary-shaped reef. This work supplies a scientific evidence for how to select the hole diameter for an artificial reef.

Fracture loads for blunt notches under mode I loading

In the present study, fracture load evaluation technique for blunt notches under mode I loading is investigated using the mean stress based line criterion. Considering the effect of notch root radius ρ, a new fracture evaluation method, applicable not only for the V-shaped notches but also for other notches such as shallow notches, is developed, For a large notch root radius ρ (i.e. ρ>ρ|Cri-1), the notch fracture can be evaluated by a simple rule that the fracture occurs when the maximum stress σmax reaches the material ultimate tensile strength σC. If ρ is large adequately such that ρ|Cri-1>ρ>ρ|Cri-2, the notch fracture is evaluated as the fracture problem of a circle hole in an infinite plate. Here, ρ|Cri-1 and ρ|Cri-2 are the critical values for ρ to satisfy the σmax-alone condition and the ρ-alone condition, respectively. Moreover, as long as the V-notch condition is fulfilled by the notch geometry, the notch fracture under mode I loading can be treated as the fracture problem of V-shaped notches and evaluated by the generalized notch stress intensity factorKIV,R or the maximum stress at the notch root σmax. Whether the σmax-alone condition, the ρ-alone condition or the V-notch condition is fulfilled is mainly determined by the ratio of the characteristic length d0m to the geometric size of notched specimen.

Numerical Investigations of Stress Concentration in Reinforcement Steel Structure by Composite Overlays

Abstract The stress concentration observed in the vicinity of cut-outs and holes in structural elements significantly influences the fatigue endurance of machines subjected to cyclic loads. Numerous studies have been made so far to improve this situation and increase the structure lifetime. Several design recommendations have also been worked out to avoid the problem of premature failure. The proposed article illustrates the influence of the composite overlays applied around the cut-outs made in flat steel constructional elements subjected to axial tension. The detailed study concerns the reinforcement made from the FRP (fibre reinforcement polymer) composite applied around the notches. Two types of composite materials were used, namely: TVR 380 M12/R-glass (glass fibres embedded in epoxy resin matrix) and AS4D/9310 (carbon fibres embedded in epoxy resin matrix). In the first step, the detailed numerical studies (finite element analysis) were performed for the steel samples (with no overlays added) with cut-outs made in the form of circle, square and triangle hole (the last two with rounded corners). The results of these studies were compared with the existing analytical solutions with respect to the stress concentration factors (SCF) estimation. The relatively good conformity was observed when using dense meshes of finite elements placed around the void vicinity. In the next step, the composite overlays were applied around cut-outs and their influence on the stress concentration was investigated. The influence of the fibre orientation, numbers of layers, sizes of the composite overlay used were considered. It was proved that the application of composite overlays evidently decreases the stress concentration around the notches.

Spider Web-Like Phononic Crystals for Piezoelectric MEMS Resonators to Reduce Acoustic Energy Dissipation

Phononic crystals (PnC) are a remarkable example of acoustic metamaterials with superior wave attenuation mechanisms for piezoelectric micro-electro-mechanical systems (MEMS) resonators to reduce the energy dissipation. Herein, a spider web-like PnC (SW-PnC) is proposed to sufficiently isolate the wave vibration. Finite-element analysis is performed to gain insight into the transmission property of finite PnC, and band characteristics by infinite periods. In comparison with the circle hole PnC at a similar bandgap, due to its already very lightweight PnC structure compared with previously reported PnCs, the proposed PnC offers a significantly lighter weight, smaller lattice constant, and greater energy leakage inhibition. More specifically, the resonator with the SW-PnC plate as the anchoring substrate exhibited a quality factor as high as 66569.7 at 75.82 MHz.

Characteristic Mode Cancellation Method and Its Application for Antenna RCS Reduction

This letter proposed a characteristic mode cancellation method for design of an antenna radar cross section (RCS) reduction. Two kinds of subarrays whose unit cells are composed of a square patch with a circle hole and a cross patch, respectively, are designed. With the characteristic mode theory, the currents represented by the characteristic modes of two subarrays flow in an opposite direction. By arranging two subarrays into a checkerboard patterned array, cancellation of their characteristic modes is achieved and, thus, the resultant RCS of the whole array is greatly reduced. The checkerboard array is integrated with a microstrip antenna to reduce its RCS. The simulated and measured results are in good agreement and show that with the checkerboard array, the operating band of the reference microstrip antenna covering 8.32–9.32 GHz keeps unchanged, and the −10 dB broadband RCS reduction both in band and out of band of the microstrip antenna is from 6.4 to 21.4 GHz with an in-band gain increase of 1 dB.

Finite element simulation on the reflection and transmission of the lamb waves across a micro defect of plates

This paper presents a theoretical and finite element (FE) investigation of the generation and propagation characteristics of the fundamental Lamb waves symmetrical mode S0 and anti-symmetrical mode A0 after testing with different types of defects in the plates. The reflection and transmission of Lamb waves at a micro symmetry defect and asymmetry defect are analyzed numerically in the two-dimension (2D) model. Mode conversion of Lamb waves can occur upon encountering the asymmetry discontinuities leading to newly-converted modes apart from wave reflection and transmission. When testing the symmetry defects, the reflection and transmission waves have no modal separation phenomenon. To describe the mode conversion and reflection and transmission degree, and evaluate the micro defect severity, a series of defects are simulated to explore the relationships of defect reflection and transmission with the length and depth of a defect in the 2D FE model. In the three-dimension (3D) FE model, the straight-crest Lamb waves and circular-crest Lamb waves are simulated and researched by contrast analysis. Then the straight-crest Lamb waves are motivated to study the scattering laws of Lamb waves interacting with the circle hole defects and rectangular hole defects. S0 mode and SH0 mode are contained in the scattering waves after S0 mode testing the through holes defects. Corresponding mode energy percentages were analyzed at different micro defect severities changed in different ways. Simulation results illustrated that the modal energy percentages varied in a different character and provided support for the analytically determined results of Lamb waves in the non-destructive testing and evaluation.

Elastic Buckling Behavior of Thin Plate with Circle Holes under Axial Compression

The stability of members will be affected because the stress concentration resulted from the holes in thin plates. Elastic buckling performance of the perforated circle plate under axial compression is analyzed using a general finite element software ABAQUS in this paper. Results show that the buckling stability coefficient of plate is significantly low when the hole locates at the short side of the plates. The buckling stability coefficient of plate will decrease with the increase of the dimension of holes when the hole size is less than a certain value. The buckling mode of plates will change because of the dimension of holes. Finally recommended calculate formula of buckling stability factor k of perforated circle plate under axial compression is presented based on parameter analyse.

Large-scale and contact-free fabrication of microwell arrays based on electro-pressure of depositing ions

Microwell arrays are showing great potentials for various optoelectronic and biological applications. However, large-scale fabrication of microwell arrays remains a big challenge to modern micro- and nanotechnology. Here, we report a novel fabrication method that can produce massive aligned microwells in a cost-effective way. With using ionic wind, the hole arrays of pre-fabricated masks can be projected on polymer films and form microwell arrays in a contact-free way, and at high efficiency. Thousands of microwells can be rapidly fabricated in several minutes with their parameters, such as shape, size, and density, being widely tunable, through adjusting the mask’s design and its location in the ionic wind. The fabricated circle and square holes in microwells perfectly replicate the features from the mask, thus being successfully used to trap suspension cells and culture them sustainably till significant cell patterns are formed.

Comparative Study on Flexible Link Aerator Using Arduino Programming and Dissolved Oxygen Meter

This paper presents the comparative study on flexible link aerator using Arduino programming and dissolved oxygen meter. To maintain the level saturation of dissolved oxygen it is importance to control the mechanism. For control the flexible link aerator for generating dissolved oxygen it will collaborate with Arduino system. Arduino will attach together to flexible link aerator and give the instruction to motor according to the level of saturation dissolved oxygen had been set on it. For set the level of saturation dissolved oxygen it will design the instruction suitable for the Arduino programming language. To reduce the steady state error it will work with PID controller to achieve the best performance on flexible link aerator. The experiment will be conducted in the model scale tank. On Arduino the programming will be set into the rate of dissolved oxygen between 18 O_2% and 20 O_2%. The mechanism of flexible link aerator is by using flexible link with circle holes. The Arduino controller program and the dissolved oxygen meter show is difference value because the result dissolved oxygen meter is considering the temperature. The result of dissolved oxygen level and the PID controller parameter are shown based on the current dissolved oxygen level during the experiment. The flexible link aerator can control the dissolved oxygen level by using Arduino and the motor of flexible link aerator is controlling by PID controller.

Measurement method of LCD surface deformation for smartphone based on optical vision sensing system

In this paper, a machine vision based smartphone LCD(Liquid crystal display) surface deformation measurement method is proposed through applying the designed optical sensing system and a corresponding inspection algorithm. In such an approach, the images of LCD surface are firstly acquired by the vision sensing system, which involves a precision plate with evenly distributed circle holes and a semi reflecting mirror. Then, the preprocessed image is analyzed by utilizing the inspection algorithm and thus the maximum deformation can be obtained. In the validation experiment, a smartphone LCD with deformed surface is used as the measurement object and this maximum deformation of the LCD surface approaches about 4.5μm in the row direction and is less than 3μm in the column direction. Experimental results show that not only the magnitude of maximum deformation of LCD surface can be measured but also the deformed position can be determined by applying the proposed technique. Compare to existing systems and methods, the presented technique is a more economical solution as it is easy in operation and lower in price.

Effects of hole shape on impingement jet array heat transfer with small-scale, target surface triangle roughness

Considered is the addition of special surface roughness patterns to impingement target surfaces to improve the effectiveness and surface heat transfer augmentation levels of impingement cooling. Three different impingement hole shapes are employed within a jet array: circle, racetrack, and triangle. These are designed so that all three hole shapes have the same hydraulic diameter. Different sizes, different shapes, and different distributions of surface roughness elements are utilized, including arrays of small triangle roughness, with different roughness heights, employed with and without the addition of large pin roughness elements. Data are presented for impingement jet Reynolds numbers of 900, 1500, 5000, and 11,000. Overall, the racetrack hole configuration generally provides approximately the same heat transfer augmentation as the circle hole configuration, with slightly better performance, under some conditions. The triangle hole configuration provides lower heat transfer augmentation, compared to both the circle hole and racetrack hole configurations. The addition of small triangle roughness to the target plates shows an increase in heat transfer augmentation, compared to the baseline target plate, for both the circle and racetrack hole configurations. For the triangle hole configuration, the addition of small triangle roughness generally shows negligible or negative improvement, compared to the baseline target plate. Also illustrated is significantly different Reynolds number dependence for impingement cooling, as hole shape changes from circle to racetrack, and triangle.

Fundamental study of mechanism of band gap in fluid and solid/fluid phononic crystals

Phononic crystals (PCs) have possessed outstanding features to control/manipulate the propagation of the acoustic/sound wave. In this paper, the local resonant elements, such as local resonant cavity in fluid PCs and local resonant inclusion in solid/fluid PCs, are introduced. The effect of geometry parameters, Poisson's ratio, Young's modulus on the band gap solid/fluid PCs are investigated in detail. It is found that wider multiple band gaps are obtained for the fluid PCs with local resonant cavity of “+” hole compared with square and circle holes. More importantly, the very low-frequency band gaps can be obtained by introducing the local resonant inclusion with consideration of fluid-structural interaction for solid/fluid PCs. In addition, we have compared the sound transmission loss in fluid and solid/fluid PCs. The numerical results have clearly indicated that solid/fluids PCs with consideration of fluid-structural interaction can block the propagation of stress wave effectively compared with fluid PCs. The theoretical study and numerical simulation conducted in this work have provided a new avenue to design more innovative fluid and solid/fluid PCs.

Evaluation and experimental study on the sealant behaviour of double gaskets for shield tunnel lining

As waterproof joints are essential for shield tunnel segmental lining, double gaskets have been adopted for certain tunnel segments with high ground water pressure to prevent water leakage. To investigate the leakage behaviour of double gaskets in shield tunnel lining with joint opening and offset combination, mechanical and leakage tests were conducted on double gaskets subjected to water pressure. The linings are made of bolted and precast concrete with double gaskets, and the two gaskets are different sizes, but both have open bases. The mechanical test results revealed that three distinct phases are observable in the gasket load deformation curve, due to the process of gasket compression. Inappropriate design parameters for the gasket can result in the segment spalling around the gasket groove in field. In this study, improved parameters, including the diameter of circle hole inside the gasket and the hardness of the gasket, are presented with the goal of preventing segment damage. The experimental sealant test results demonstrated that the joint opening has a significant effect on the gasket leakage capacity: with increasing joint opening, the gasket sealant capacity decreases. The leakage mechanism of the double gaskets is also elucidated.

Stress distribution analysis and optimization for composite laminate containing hole of different shapes

This paper proposes a flexible analytical method to obtain the circumferential stress of hole's edge in composite laminate, which can provide convenience for the optimization of hole's shape meanwhile. Firstly, different shapes of hole are expressed in one map function based on the conformal transformation. Secondly, stress function method is applied to the anisotropic elastic theory, which derives the stress expressions to calculate arbitrary point's stress in equivalent anisotropic plate. Thirdly, the circumferential stress of hole's edge in composite laminate can be calculated by combining the map function with the stress expressions. This method is verified by finite element simulation for the hole of circle, triangle and square, which draw a conclusion that circle hole is not always the best choice for aeronautical structure design. Meanwhile, an optimal shape of hole is obtained by the mentioned method with help of gradient descent algorithm and mesh deformation technique. The optimization result is validated by simulation and it meets the conclusion identically, which also means the method's accuracy is reliable.

Controllable multiple plasmonic bending beams via polarization of incident waves.

Plasmonic bending beams, which preserve their spatial shapes while propagating along curved trajectories in metal-dielectric interface, offer important applications in the fields of fiber sensor, optical trapping, and micro-nano manipulation. In this work, circular hole array, as a local point-like sources of surface plasmon polaritons, is designed on the metal film to generate multiple plasmonic bending beams. The electric field intensity of multiple plasmonic bending beams is controlled by polarization angle of input light. In addition, the electric filed intensity of multiple plasmonic bending beams relies on circle hole radius. These findings provide guidance in the design and optimization of plasmonic bending beam generators.

Numerical Investigation on the Two Phase Flow Behaviors in Supercritical Water Fluidized Bed with Swirling Flow Distributor

ABSTRACTSupercritical water fluidized bed reactor is a promising in the clean and efficient conversion of coal, and the distributor is one of the key component for the heat and mass transfer enhancement. However, the optimization study for the distributor in supercritical water fluidized bed reactor has been seldom conducted due to the special thermal properties of supercritical water. In this work, the swirling flow distributor was designed for its optimization for heat and mass transfer inside a supercritical water fluidized bed reactor. The swirling flow can be generated by the concentric circle or triangle type hole distribution in distributor with 0 or 45° intersection angle between the fluid inlet velocity direction and the distributor plane. The computational particle fluid dynamics (SCWFB) method, which has quick calculating speed and high accuracy, was used in this work to study the particle-fluid two-phase flow behaviors inside SCWFB with swirling flow distributors. Investigations were made to reveal the influence of the hole distribution type and intersection angle on the bed pressure drop and particle volume fraction characteristics. The results showed that the triangle type distributor with 45° intersection angle has the best fluidization performance. The conclusions drawn may has potential application for continuous and stable operation of supercritical water fluidized bed reactor for coal gasification.

Experimental Research on the Factors Affecting Fusion Zone Size and Mechanical Properties in Crack Arrest by Current Detour and Joule Heating

When pulsed current passes through the specimen containing a crack, since the cannot flow through the crack, the current has to detour around the crack tip, and the current density at the crack tip is excessively high. Owing to Joule heating, local melting occurs and a circle hole is formed at the crack tip. In this work, with 316 stainless steel as a specimen, the crack arrest experiment is performed on high pulsed current discharge device of type HCPD-I. The factors affecting the fusion zone size are studied. By making tensile test and fatigue test, relationships between the molten hole size and the crack arrest effect are derived. The experimental results indicate that the molten hole size is proportional to crack length and discharge parameter. The discharge parameter to the best effectiveness of crack arrest can be obtained.

Thermoelectric fields and associated thermal stresses for an inclined elliptic hole in thermoelectric materials

A theoretical model for the thermoelectric coupling analysis of thermal materials with an inclined elliptic hole is constructed. The extended problem of an elliptic hole under biaxial loading is also discussed. Theoretical and numerical results for the thermoelectric coupling resulting thermal stress are obtained. Results show that, for the biaxial loaded elliptic hole, the solution cannot be the linear superposition of the solutions of two uniaxial loaded cases due to the nonlinear coupling. For inclined elliptic hole, the maximum thermoelectric concentration occurs when the major axis is perpendicular to the loading direction. However, the maximum stress concentration occurs when the major axis is parallel to the loading direction. The solution of a circle hole problem is given as a special case in the framework of elliptic hole problem. The crack problem is also discussed when the ellipse degenerates into a crack. It is found that all field intensity factors exhibit the traditional inverse square-root singularity at the crack tip. The mode I stress intensity factor only depends on the applied electric current. The mode II stress intensity factor only depends on the applied energy flux when the crack line is perpendicular to the loading direction. However, in the biaxial loading case, the mode II stress intensity factor relies on the applied electric current density and energy flux. This is the first paper to conduct a strict closed-form solution for an inclined elliptic hole in thermoelectric materials.

Stress analytical solution for an infinite plane containing two holes

An analytical solution is presented for an elastic infinite plate containing an ellipse hole and a circle hole, which undergoes the internal traction along the holes and uniform tensions and shears at infinity. The solution uses the conformal transformation in complex functions, with the multiple connected region mapping onto a circular ring. The stress distribution solved for the infinite plane containing two unequal circle holes in prior literatures is the special case of this article. And contrast between the results of two unequal circle holes obtained by using the present analytical method and the Hoang's results is made in the article. As there is no analytical solution for two non-circular holes, the results obtained using the present analytical method are compared with the numerical results calculated by ANSYS. Computational examples given in this article has been analyzed to study the effect of distance between two holes, the ratio of stress in two directions at infinity, and the ratio of the major and minor axis, on the stress distribution of the hole boundary.

Perforated ZnO nanoflakes as a new feature of ZnO achieved by the hydrothermal-assisted sol\u2013gel technique

The perforated ZnO nanoflakes with high degree of crystallinity and uniformity were synthesized via the hydrothermal-assisted sol–gel technique without any template. ZnCl2 was used as a Zn-containing precursor, causing the oriented growth of particles. The observation of a hole on the facet of the as-synthesized particles was discussed in this work. XRD, TEM, and DRS were used to investigate the prepared powder and a simple mechanism was suggested to explain the hole formation on the surface of nanoflakes. As a result, the synthesized powder included pure ZnO with direct band gap energy of 3.24 eV. The range of particle size was within 1 µm in diameter and <50 nm in thickness. A circle hole with 300–500 nm in diameter was observed on the facet of the as-synthesized particles.